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Cadillac & LaSalle Club Forums => Technical / Authenticity => Topic started by: 79 Eldorado on December 11, 2021, 01:33:01 PM

Title: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: 79 Eldorado on December 11, 2021, 01:33:01 PM
After seeing what forum member Willem Bostoen "Wbostoen" added to his '76 I thought it would be interesting to integrate a gauge within the instrument cluster of the 79-85 with analog gauges. For anyone who missed it what Willem did was pretty impressive and he shared what he did within the following thread:
https://forums.cadillaclasalleclub.org/index.php?topic=166662.0

I previously test fit a 1989-92 Buick Century temp gauge (first photo below). That fit fairly well but I decided against continuing.

When I saw what Willem did I thought I would consider reviving the topic of adding a gauge. This is more of a back-burner project but there were a few things I was able start without much effort. I started by creating some sample graphics (photo2) and with cut-paste I added a sample version to a 1979 dash photo (photo3).

Next I needed to learn something about Arduino programming. I was able to get it to work today using a spare 70's EFI air/coolant temp sensor as the variable input (measured using a reference resistor). I selected that specific sensor because I know them well enough to convert the reading to a temperature (doesn't hurt that I'm making them either). It's a start and could be applied to any vehicle just by creating a gauge which fits and looks like it belongs in the dash. Of course EVERY vehicle I have other than the Cadillac already has a real temp gauge. I guess the Cadillac management decided having an actual gauge was too complicated for us.

I described the idiot light set-up to a friend as an "oh crap" light followed a few seconds later by "I guess it's time to call a tow truck" red light. He asked me if I considered simply replacing the existing sensors with lower temp sensors. I had started looking into that once before and it would be an alternative if someone wanted a very quick improvement. I would suggest moving the ~260F red light sensor wire to the lower temp sending unit (Red light would then come on at ~240F). I would then replace the red 260F sensor with one which grounds at around 210-220F. The thermostat should be a 190F stat so if my car gets as hot as 210F I would certainly like to know; 240F is too late. If it hits 240F it's an issue where you will likely see 260F 30 seconds later if you're lucky.

Scott

Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: bcroe on December 12, 2021, 10:42:46 AM
Many approaches will work.  Practice here for a long time has been
to install a compact 1.5 in 270 degree gas bulb gauge in the dash. 
Not much space taken, and works even after shutdown. 

On the 79 Eldo work is underway to install this gauge paired with a
fuel pressure gauge, which has been seen as a useful addition, esp
with fuel injection.  One problem in this case is finding enough coolant
ports for all the sensors.  Bruce Roe
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: 79 Eldorado on December 12, 2021, 11:05:21 AM
Bruce,
Yes a fuel pressure gauge would be great for diagnosing an issue as it occurs live.

On the coolant temp it would be great if I could read the resistance which the ECU is reacting to directly from the ECU (without altering the resistance). I could use any generated signal which is proportional to that resistance. Maybe the voltage could be read parallel to the sensor wires. If that were possible there would be no need for an additional sensor. I assume the ECU knows the resistance through a voltage divider set-up.

I was also thinking I could use the position currently occupied by one of the idiot light sending units. If the red light sending unit was removed we would still have the "lower" temp 240F light. I don't recall the thread size for those. I would likely place the wire for the red light on the 240F sending unit (red light would come on at 240F).

The Arduino version needs power and ideally a 5V source but it can tolerate a higher input; so a key turn without starting would display the temp.

Scott
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: bcroe on December 15, 2021, 12:32:40 AM
Quote from: 79 Eldorado. Bruce,
Yes a fuel pressure gauge would be great for diagnosing an issue as it occurs live.

On the coolant temp it would be great if I could read the resistance which the ECU is reacting to directly from the ECU (without altering the resistance). I could use any generated signal which is proportional to that resistance. Maybe the voltage could be read parallel to the sensor wires. If that were possible there would be no need for an additional sensor. I assume the ECU knows the resistance through a voltage divider set-up.

I was also thinking I could use the position currently occupied by one of the idiot light sending units. If the red light sending unit was removed we would still have the "lower" temp 240F light. I don't recall the thread size for those. I would likely place the wire for the red light on the 240F sending unit (red light would come on at 240F).

The Arduino version needs power and ideally a 5V source but it can tolerate a higher input; so a key turn without starting would display the temp.  Scott

I created a T from a block of brass threaded for a couple clamp
fittings to fit into a section removed from the fuel rail.  The third
port is pipe threaded for the electronic pressure sensor on the 79. 
The mechanical sensor in this old pic is not the compact solid state
sensor I am now promoting. 

There is a near linear voltage in the ECU coolant temp sensor ckt. 
I actually wired this to a spare op amp section of the LM124, and
the output went thru an extra connector to a triple gauge unit I
had.  There is a trick to help cancel slight non linearity.  This worked
fine.  HOWEVER I was into swapping ECUs, which killed my temp
gauge, it quit with ignition off, and the extra connector was more
wiring to deal with.  I eventually decided to go to the gas bulb gauge. 

I am not much a fan of pure digital readouts. I like moving needles
and moving bar graphs.  Bruce Roe
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: 79 Eldorado on December 19, 2021, 10:28:09 PM
Quote from: bcroe on December 15, 2021, 12:32:40 AM
I created a T from a block of brass threaded for a couple clamp fittings to fit into a section removed from the fuel rail.  The third port is pipe threaded for the electronic pressure sensor on the 79.  The mechanical sensor in this old pic is not the compact solid state sensor I am now promoting. 
Nice idea. It reminds me of the AN blocks designed for a gauge.

Quote from: bcroe on December 15, 2021, 12:32:40 AM
There is a near linear voltage in the ECU coolant temp sensor ckt. I actually wired this to a spare op amp section of the LM124, and the output went thru an extra connector to a triple gauge unit I had.  There is a trick to help cancel slight non linearity.  This worked fine.  HOWEVER I was into swapping ECUs, which killed my temp gauge, it quit with ignition off, and the extra connector was more wiring to deal with.  I eventually decided to go to the gas bulb gauge. 

I am not much a fan of pure digital readouts. I like moving needles and moving bar graphs.  Bruce Roe
I was thinking of the reference 9.5V you mentioned in another post where you explained the standard for devices like this had not been yet established when the ECU was designed (later 5V and 3.3V became the standard). I assumed that possibly the ECU has a voltage divider set-up to know the resistance of the sensor. I mean if the ECU has a reference resistor, in series, the voltage across the sensor and the reference would be proportional to each other and add to 9.5V. I was thinking the ECU would "react" to that variable voltage to know essentially read the temperature. If that is true I was thinking I could read the voltage in parallel to sensor. Since the sensor resistance is very close linear, in the range we need to read, the voltage in that range would be as well. If I know the value of the reference resistance, and the input voltage (9.5V?) I could calculate the expected voltage at sensor resistance which we have he reference temp for. Assuming that is how it works I could also measure the voltage at a known temp and that should allow me to determine the reference resistor value.

I guess maybe it's not that simple but if it is the connections could be made on the external plug going to the ECU which would mean you could change ECU's anytime you wanted without the need to re-wire.

I agree I like moving needles more than digital output for things like this. I also want it to fit the look of the instrument cluster.

Scott
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: bcroe on December 19, 2021, 10:53:57 PM
Likely a better arrangement than my first attempt, would be to
build the gauge ckt entirely outside the ECU, any ECU would
work unmodified.  I would suggest a meter circuit box which
ties into the temp coolant sensor wire on RED conn pin D, and
the sensor dedicated ground on RED conn pin G.  Pick up 12V
ignition power to run the meter on on BLACK conn pin F.  All
this from my drawings, could forward the latest 79 version. 

The ECU would supply the regulated voltage divider, you just
measure the voltage across the sensor pins and translate that
to your readout deg F.  Bruce Roe
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: 79 Eldorado on December 19, 2021, 11:13:55 PM
Bruce,
If you do have a latest circuit diagram it would be great. If the circuit is similar to what I described the Arduino could likley read the reference directly but it normally deals with a 5V reference. It has the ability to read the reference (analog in). If the ECU has a ref resistor in series I guess what I would be reading with the Arduino would be roughly half of 9.5V though. I could always use a diode to divert over a value which could be too high.

Thanks,
Scott
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: smokuspollutus on December 20, 2021, 02:29:31 PM
This is a cool idea Scott. I actually did a rendering of what that would look like years ago. It's buried on my Flickr somewhere. I like the Buick Century gauge approach. This is all a moot point for me since my car has the digital display and that slot is occupied by the fuel range display. But most of my Eldos have had the analog unit and I couldn't help but feel that the coolant temp idiot light was a last minute addition considering the ample space in the info centers for another light and that the hole is a perfect mirror of the fuel gauge. Maybe a fuel gauge could be repurposed for the task? Or swap the Buick century guts to a spare Eldo fuel gauge body so it will mount up cleanly in the cluster?
Title: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: bcroe on December 20, 2021, 02:44:09 PM
Quote from: 79 EldoradoBruce,
If you do have a latest circuit diagram it would be great. If the circuit is similar to what I described the Arduino could likley read the reference directly but it normally deals with a 5V reference. It has the ability to read the reference (analog in). If the ECU has a ref resistor in series I guess what I would be reading with the Arduino would be roughly half of 9.5V though. I could always use a diode to divert over a value which could be too high. Thanks, Scott

Easy enough to find a voltage which translates directly to a coolant temp
when the ignition is on.  Tell me again just how you want to drive a display
of this temp?  Bruce Roe
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: 79 Eldorado on December 20, 2021, 05:07:14 PM
Quote from: bcroe on December 20, 2021, 02:44:09 PM
Easy enough to find a voltage which translates directly to a coolant temp when the ignition is on.  Tell me again just how you want to drive a display of this temp?  Bruce Roe
Bruce,
The Arduino can move a servo with a PWM (Pulse Width Modulated) signal. So far I've been using the voltage divider concept to measure the resistance (through voltage measurement) in one of my sensors versus a fixed known 1000 Ohm resistor in series. Once the voltage is read (input pin) a simple program relates measured voltage to resistance and temperature. I then map the voltage accordingly to the servo to move to the proper temp.

Quote from: smokuspollutus on December 20, 2021, 02:29:31 PM
This is a cool idea Scott. I actually did a rendering of what that would look like years ago. It's buried on my Flickr somewhere. I like the Buick Century gauge approach. This is all a moot point for me since my car has the digital display and that slot is occupied by the fuel range display. But most of my Eldos have had the analog unit and I couldn't help but feel that the coolant temp idiot light was a last minute addition considering the ample space in the info centers for another light and that the hole is a perfect mirror of the fuel gauge. Maybe a fuel gauge could be repurposed for the task? Or swap the Buick century guts to a spare Eldo fuel gauge body so it will mount up cleanly in the cluster?
Anthony,
I thought the Century gauge looked close but in the end it would have been a fair amount of work for something I wasn't certain I would be happy with. I felt I would have likely tried to disassemble it and create a new custom face plate. That would be a lot to do for a single car and nothing easily offered to others as the Century parts aren't that readily available either.

I'm not a gauge expert but they need to be tailored to the particular resistance range. The fuel gauges are something like 0 to 90 Ohms by memory. I don't know for sure but I don't think that's a range which is easily found in temp sensing devices which vary resistance. The EFI sensors, as an example, are around 1000-2000 Ohms in the temp range we need. So the fuel gauge might work but we would need additional circuitry to translate what the sending unit is reading to what the gauge would see as equivalent to 0-90 Ohms (or the resulting voltage). Spare fuel gauges for our cars I suspect are not easy to find either.

The project Willem worked on was digital. If you could find a place where it fit the look of the digital dash I'm sure his concept could be used on your car. He even customized his graphic. He's the one who turned me on to the Arduino idea. As long as there's a way to fit the parts in the space I think I could get a local sign/graphics place to create a custom overlay. I may paint one myself to start though.

I would like to retain at least one of the idiot lights but I think I could set things up so it would be visible despite the gauge. I'm not certain yet.

Retaining both lights would be possible if the voltage signal comes directly from the ECU; at least 1979. That said we don't need 2 lights which are 20F apart. I could fairly easily design a sensor to go in place of one of those existing sensors. If they're already 1/4 NPT the 1976-79 EFI coolant sensor would work without modification. One problem with using the ECU signal is the gauge only works for the 1979 then. If I replace an idiot light sensor it can work on anything from 1979-1985 (I guess?).

Scott



Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: bcroe on December 20, 2021, 06:20:12 PM
All the 70s Cad EFIs use about an 1100 ohm resistor from 9.5V to the temp
sensor, current flowing to the ECU ground.  My notes say the sensor voltage
is about 3.96V at 0F, 5.38V at 200F.  You could zero that in a bit on your setup
and find other values for a gauge.  It is not perfectly linear, but most temp
gauges on close examination are not either.  Sometime an extra bend can be
added to get what is wanted, pretty common practice from way back. 

I gave the pin numbers, you want to use that ECU ground, as random body
grounds will shift some with things like alternator current to headlights or blowers. 

Use a fuel gauge with recalibrated scale?  Once you have curves for the output
of the sensor and input of the gauge, all you need is an amp with that transfer
function, not difficult.  The amp may run a bit of power for that gauge. 

You can do the same with any engine, but supply your own voltage, resistor, and
sensor to pick up the temp.  A current source might give a bit more linear output
than a resistor.  If you want it to work without ignition power, you will
need to find another way to turn it off and not run down the battery. 

Bruce Roe
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: 79 Eldorado on January 16, 2023, 04:57:21 PM
After touching on this under a topic Cory started it seems like using a traditional gauge shouldn't have been dropped as a potential idea without more investigating...
Link to Cory's topic:
https://forums.cadillaclasalleclub.org/index.php?topic=170475.0

I found a gauge which will fit in the position to the right of the speedometer and the gauge face doesn't even look that bad. It's a single wire gauge. I can come-up with a holder to mount it securely but without changing the gauge face, easier to leave it the way it is, you will very likely be able to see the edge of the round face. The needle can be painted to match the other needles.

I was concerned about the lighting in that area of the dash but I found the photo I took after changing all of my dash lights and there is a light source there.

A gauge face could be made in the same shape as the "Coolant Temperature" panel graphic already there. A decal with lines, maintaining "Coolant Temperature" could even overlay the original panel. The material of the original looks brittle though and holes need to be added to put the pointer and the screws through. The original panel as well doesn't have much structure.

Conclusion:
Working traditional gauge doesn't look that difficult... there are a lot of different ways to go and some are easier than others.

Any thoughts? I initially thought a sticker/decal would make the black backing appear too gloss like but I'm not certain that's true. Can the gauge face be swapped without risk of damage?

Scott
OE Dash lights at night:
IMG_20190518_222737.jpg
Replacement gauge without changing the face just sitting in place for now:
2023_01_15 3_32 PM Office Lens.jpg

Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: TJ Hopland on January 16, 2023, 05:59:33 PM
That doesn't look bad.  Mask off the roundness and it would look better.  What's it gonna look like in the dark with it lit tho?   That may be where it falls apart.
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: bcroe on January 16, 2023, 07:38:37 PM
That looks pretty good.  It occurs to me, another
gas gauge might fit well over there, needing new
scale.  But they are not very sensitive, would
need a proper drive ckt.  Bruce Roe
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: 79 Eldorado on January 16, 2023, 11:03:53 PM
TJ,
When I had it apart I didn't realize there was "another" light source, other than the coolant bulb, until I saw my old photo in the dark. I suspect though it would at least be as bright as the photo. I can probably make the mask hide it a little better but I didn't want the mask to give the appearance of shrinking it too much.

Bruce,
Cory mentioned using the fuel gauge as well but I don't love that idea. I would still need to change the face plate, come-up with a different sending unit and I also realized GM error proofed the mounting screws to seemingly prevent someone from mounting the gauge on the wrong side. On top of that there's a limited supply of those old fuel gauges.

I worked on the CAD version of the graphics. I spent hours before I realized the file font I was using seems to have an issue with the "H" as well as at least one character in the words "Coolant" and/or "Temperature". So I have a perfect "C" and that's it. What a time wasting exercise. Powerpoint must have a separate font file or it simply doesn't have the issue which FreeCAD has. I did create the lower divided graphic and part of the temperature bulb.

Another thing I thought of was building on Cory's idea of using that blank panel on the 1979. we could mount a couple of gauges in that position.

Scott
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: fishnjim on January 17, 2023, 11:02:04 AM
I generally like gauges, but in this case I don't think it makes much difference to have a warning vs indication.  I doubt the muckitymucks had much say over the engineering/design depts.  Cost targets yes, but dictating instrument layouts, doubtful.
The coolant system is capable of mild pressurization so it'll see temps over 220F as normal and some have catch tanks so there's no issue of overflow.  Depends on the cap pressure when it'll overflow to protect the integrity of the system.
You have to look at likelihood when applying instruments and how often is this a problem?  Regular inspection of the fluid level is easy.  I think some people will not understand what's going on/how cooling system works and it they see the temperature go up or down, they'll head to the service window and drive them nuts.   It's not controlled like the thermostat in your house.
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: 79 Eldorado on January 17, 2023, 08:11:19 PM
Jim,
I've had a few situations where a gauge alerted me that something strange was happening before I had catastrophic issues. There are optional or standard gauge packages for almost everything GM makes...except these old Cadillacs. The Toronado of the same year, also an E-Body, had a coolant temp gauge even without ordering the optional gauges which were available. I could see someone making the decision going through the same thought process that you mentioned but doesn't that say all other owners are capable of understanding a gauge but Cadillac owners are not?

There are 2 lights on the Eldorado. As I recall they're 20 degrees F apart but the lower one is already higher than I've seen the Toronado run assuming there was no issue.

Scott
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: bcroe on January 17, 2023, 10:08:24 PM
That gauge keeps me up to date on the capability
of the cooling system.  It will tell me when the
situation is getting too difficult.  And it will
tell me when it is time to make adjustments (take
it easy), and if the adjustments are sufficent
to get back into safer territory.  Yes I have
rolled the windows down and run the heater at
max on a very hot day.  But got home. Bruce Roe
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: eldofever58 on January 19, 2023, 07:52:37 PM
Bruce, here's a pic I took the other day subbing the fuel gauge. From what I could tell, mounting would be pretty easy- Cut a rectangular backer out of thin gauge aluminum, punch a hole in the center, and drop the gauge in. Drill two holes to match the cluster bosses and you're set. But to Scott's point, they are getting tougher to find. I see digital clusters 2:1 at the yards. I also suggested using the low fuel light as an overtemp attention-getter, but a driver circuit for the works would need to be drawn up.

(https://ht4100.com/temp/IMG_5855.JPG)
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: 79 Eldorado on January 19, 2023, 09:48:11 PM
Cory,
Cool that you tried moving a fuel gauge over. I've been working on CAD modeling the parts. The following capture is the aftermarket gauge body I found placed behind the idiot light mask and positioned so it should fit properly within the cover mask and be visible.

Some things I noticed:
-The idiot light mask looks amber in color so I suspect that's the orange light which comes on before the red light. I couldn't recall which was which.
-The OE mask is very thin. That plus better location relative to the plastic holder might be why they added those bottom locating bayonets. It shares the same screws though. In the spare dash I bought those bayonets weren't even inserted as they should be.
-The plastic part for placing the idiot light mask seems really over complicated. I wonder if some of that was to seal the light of the warning bulb from "leaking" to other areas of the instrument panel when the warning light lights. I suspect it must have been for that reason. I was going to create some form of that part to cradle the gauge body but the entire part could possible be eliminated or greatly reduced.
-If I use a decal or transparent stock sticker I could likely cut a window in the gauge face so that the amber/orange warning light still works through the gauge face.

Once everything is modeled I don't think this would be terrible to implement. That aftermarket gauge has a low-limit stop pin for the gauge needle. Does anyone know if that's really necessary? I could probably braze a pin in, I mean literally a sewing pin, and cut it off but that's the closest thing I can think of unless those pins are available someplace.
TempGaugeConceptonOEMask 19JA2023.JPG

Scott
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: 79 Eldorado on January 22, 2023, 11:15:40 AM
All,
Here's the first 3D test print of the gauge holder. It wasn't easy to measure everything relatively from the deeper area to the face. There are locating pins at the bottom. Those control the location but they need to be closely aligned with the screw hole locations on the face. It looks like I got most things spot-on but I need to move the face down, relative to the body, to get the screws to align properly. As you can see the lower right corner is close to the screw boss. The lower right corner of the OE part is very similar. I will alter the geometry slightly on that corner before moving the face, and holes, down.

I was very happy with the first test print. I still need to determine where to add a hole in the gauge holder for the gauge wire. That gauge wire will also need to go through the instrument panel.

Something I realized while doing this was the OE "gauge holder" was needed to only block any light from illuminating the amber idiot light at night when the normal dash lights were on. The normal light which illuminates that part of the dash is above the gauge holder "cup". The OE design has a rounded triangle as part of the face plate. I assume that reduces light over the idiot light area so I eliminated the obstruction.

Here's a photo of the test fit.
2023_01_22 10_37 AM Office Lens.jpg

Scott
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: bcroe on January 22, 2023, 12:45:30 PM
Am waiting to see what mechanism you will put in there.  With
some electronics, a single temp sensor could drive it, with the
Red signal coming from the same electronics.  We did something
like that for the 57 Eldo gauge fix. 

While your Olds intake has spots for a lot of coolant sensors, they
are not unlimited.  All might be used on my car, a pipe thread drill
and tap on the intake manifold done.  I typically have a switch for
a HOT light and a resistive sensor or gas tube for a dial gauge. 
But the 79 E also wants one for the EFI, and I had a second for
an after market ECU experiment.  That was too many, the after
market sensor is now gone. 

One possibility here is connect to the wires of the EFI coolant
sensor, the operating voltage can be directly translated to temp. 
That then used to drive a gauge.  One less sensor. 

A problem here with my cars having so many miles, driven so
much at night, is the incandescent dash illumination bulbs get
hot and eventually distort the plastic mounts.  Contact may be
lost.  And of course they get black/burn out.  My conclusion is
that white LEDs might be the cure.  But LEDs do not have an
omniudirectional light pattern, so some experimentation is
needed to get it right.  That might be part of this project. 
Bruce Roe
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: 79 Eldorado on January 22, 2023, 01:25:03 PM
Bruce,
Before I started designing the holder I found the aftermarket gauge which fit (guessed and it worked). The holder is designed for that gauge specifically and I will as well create a custom face plate. I also found the sending unit for the same gauge. It's very small diameter and single wire. Take a look at the photo attached below. It was one I had from when I was working on the intake. There is a large brass plug partially blocked by the oil fill cap in the photo. That position is not used on the EFI cars. I plan to design a brass adapter bushing for the sending unit and use that position. I think most Olds intakes have that position.

One other thing I thought about was using the amber warning light position. I thought possibly an adapter could be plugged into the dash light socket and the same wire could be used. The sender for the amber light would be replaced by the sender I found. I don't think they're the same size though. I don't recall which one is used for the amber light. One of the ones used is the position between the EFI coolant sensor and the thermostat housing; not certain if that's the red or the amber one though.

When I changed the lights in my Eldorado dash I thought about LEDs but my experience with them is some do not dim properly with a dimmer, seems to take a specialized version, and second the life isn't always up to the advertising. I had a 2010 BMW 3 series in Europe and the rear taillights were sealed because who would ever need to change a bulb if LEDs are used (sarcastic)? Well a single LED went bad in one and the entire light was garbage. It then happened on the other side a year later. The original BMW replacement, single side tail lamp, was around $700. An electrical shop tried to repair one of the failed LED assemblies by hot knife cutting part of the rear of the assembly out but the repair lasted about 6 months. Finally an aftermarket company created replacements for something like $100 per side. I do have some Phillips home LED bulbs which work well on a dimmer but prior to those I tried a different brand and while they were advertised as dimmer compatible they were not. That said if someone had an LED which they know works with a dimmer I could certainly try them.

Intake350z FelPro1356.JPG
Scott

Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: bcroe on January 22, 2023, 05:33:12 PM
Scott,

Yes every Olds intake here has the 3 positions, just use an
adapter (or tap it out) to get the right size.  And you have solved
the gauge issue.  Will the original bulb function also be
included in the design?

The LEDs have a different voltage response curve, may only
agree with incandescent at max.  If you have 1 LED in series
with a resistor, it will not be so bad.  Stack more LEDS in series
and it is more efficient, but the curve gets worse as it is
dominated more by the LEDs and less by the series resistance. 

I never dimmed those lights much, so I have just been using
LEDS set as I like and putting them on an undimmed tail light
circuit.

As for BMW, lets just say I would never own one.  Bruce Roe
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: 79 Eldorado on January 22, 2023, 05:49:41 PM
Bruce,
The plan is to keep the idiot light functioning with the gauge. I plan to add a window in the face plate, in the area of the temp bulb graphic, and then hopefully I can get some orange/amber material possibly as the sticker/decal stock. I know the bulb/window will work but I need to see what's available regarding labels.

The LEDs just seem like more trouble than they're worth.

Scott
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: 79 Eldorado on January 25, 2023, 09:05:23 PM
Cory/Anyone,
Do you happen to have a photo of the dash with the instrument panel removed? The gauge wire needs to go through the light blue gauge holder and I'm wondering which area has sufficient clearance for the wire. I was thinking through the back of the blue holder (front relative to the car) or the top. I see locating features on the back and I know the dash slides in but I don't have a reference for the clearance around that part.

I wouldn't necessarily care now but I need to add a grommet/hole in my holder and where the wire comes in can make one location better than another. If it enters the rear it could come through the extreme right side of the speedometer area. If it comes from the top it could come in above the gauge. I guess I can also try to locate my clearance hole so it works ok with either location and hopefully there will be dash clearance in one of those areas.

Thanks,
Scott
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: eldofever58 on January 26, 2023, 07:51:50 PM
Scott, have a look at my speedometer swap page, there are a few pics from different angles with the speedo cluster removed. The area where the connector passes through for the digital speedo head looks like a decent spot on the analog cars.  https://ht4100.com/speedoswap.html (https://ht4100.com/speedoswap.html)
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: 79 Eldorado on January 27, 2023, 05:30:54 PM
Thanks Cory!

When I looked at those photos I noticed that the back of the dash must have close clearance because those push-in ribbon connectors would require close proximity to what they plug into. It was interesting to see the green wire tucked-in. The green wire appears to go to the idiot light position and sending units often have green wires. I was even planning to use a green wire.

I placed the grommet in a position which would be good for a wire coming in any of the 3 places I assumed it would need to; left side of my holder facing the side of the speedometer. That will allow the wire to have pretty direct access if it comes through the speedometer area or in the idiot light area as well as either from the rear or the top of the blue instrument cluster holder.

Scott
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: 79 Eldorado on January 27, 2023, 09:58:32 PM
I think I'm satisfied with the graphics now. There were issues with some of the characters in the font I was using so I selected another one which looks a lot like the fuel gauge font for "Coolant Temperature". I added a warning triangle with an exclamation mark. The idea is that area will be transparent red and so if the light comes on the triangular outline will light and as well the exclamation mark. I thought red would look nicer than amber and the warnings will still look different from one another.

Here's a photo with a paper copy printed out in very close to the correct size and position.
2023_01_27 8_16 PM Office Lens.jpg

Scott
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: 79 Eldorado on January 28, 2023, 12:40:41 PM
I had a revelation this morning and not a good one. I was wondering how a single wire could possibly function. Well it seems it cannot or does not in the case of this gauge. The single wire is just the only easily recognizable connection. The gauge still needs normal power and ground. I think I must have had hysterical blindness. The gauge has 2 receptacles for what are likely 2.5mm pins. Those pins go into the back of the gauge. The center threaded stub, coming from the back, holds the gauge to one of the flexible copper/plastic circuit backings and creates the third connection.

That probably means that gauge holder I spent so much time on needs to change and I need a connector for what should be three wires. Kicking myself because I questioned it when I saw it and I should have questioned it again when Bruce asked a question which should have given me another chance to evaluate what I thought I was seeing.
2023_01_28 12_28 PM Office Lens.jpg
Scott
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: eldofever58 on January 28, 2023, 01:06:34 PM
If I understand correctly, your printed housing won't accommodate the additional connectors? Since this is going to be custom and "permanent", I'd probably remove the gauge backshell and solder the +12 and Grd wires directly to the contact areas, reinstall the shell, then run those wires over to the fuel gauge for pow/grd. No connector protrusions to worry about.
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: 79 Eldorado on January 28, 2023, 01:42:07 PM
I was trying to maintain the idiot light warning function else I could have totally eliminated the holder. That seems to be the only real reason for the gauge holder. In the OE application the "gauge holder" just blocks the normal dash light, always on with lights, from back lighting the amber idiot light. The idiot light specific bulb is boxed inside of the "gauge holder" which isolates that area. My part was a redesigned to be an actual gauge holder, still only needed to isolate the warning light, but for the gauge to fit in that location I needed to move the bottom wall down so that the gauge face would be properly positioned in the window. Moving the gauge down avoids the need to trim the black plastic, likely fragile, instrument panel cover panel.

I think I really only need to make one area deeper in the gauge holder. I was taking a closer look after I posted and it looks like the way I have it now it would be close; another 2 or 3 millimeters deeper in the area I bumped-out for the the gauge and it would likely work if there isn't already enough room now.

That style receptacle probably has an advantage because the part of the terminal sticking out can be flat like a nail head which would be easy to solder a wire to. I cannot find a loose connector but I saw a photo of the terminal holder and it has 2 pins outboard of a center hole. The connector goes over the stud and the nut keeps the pins from pulling out.

I do think it would probably be easiest and acceptable to solder the power/ground to the existing circuit board because every lamp in the cluster needs the same.

Here's a capture of my current version of the gauge holder. That barrel bump-out area might need to be deeper.
GaugeHolderCapture 28JA2023.JPG
Scott
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: eldofever58 on January 29, 2023, 01:15:42 PM
Ah, didn't realize you were keeping the warning light with the gauge. Should things not work out, you could always populate the other Coolant Warning light location in the left Info Center panel.

(https://ht4100.com/speedohist/79InfoLeft.jpg)
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: bcroe on January 29, 2023, 05:10:31 PM
Quote from: eldofever58Scott, have a look at my speedometer swap page, there are a few pics from different angles with the speedo cluster removed. The area where the connector passes through for the digital speedo head looks like a decent spot on the analog cars.

Nice guide to the digital vs analog change.  I was
well aware that the tank sending unit typically
reads full for about the first 1/3 tank, then drops
like a rock.  Not much use for calulating stop
points.  One of the things I always do is pull the
sender and modify the arm, so the float will just
touch the top and the bottom of the tank.  That
makes it quite accurate, can say within a gallon
what a refill will need.  Probably makes it equal
to the digital pickup.  Speedo gets callibrated
a lot better, and a few other things.  Bruce Roe
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: 79 Eldorado on April 08, 2023, 12:13:33 PM
Update:
I got some stainless gauge faces cutout with a warning triangle outline plus an exclamation point in the middle of the triangle. I then had labels made to my design. The following photos are of that actual gauge pictured above but with the new face plate (needle painted and moved over). The warning triangle has lithographers dark ruby red film over it. The rated temperature extremes, of lithographers tape, are not as much as I'd like but it seems the temp range is based on strength and in this application it's basically being used as window tint. If the warning light comes on an outline red triangle should light with a red exclamation mark in the middle.

It was a bit of a challenge to get everything refined to fit nicely but I really like the way it looks. I think it looks as if it could have been there from the factory (IMO should have been there from the factory).

There's still some work to do. I plan to make an adapter for the sending unit to fit the more common NPT size in manifolds.
2023_04_08 11_55 AM Office Lens.jpg

Scott
Title: Re: Adding an actual Coolant Temp gauge to 79-85 Eldorado
Post by: bcroe on April 08, 2023, 06:18:00 PM
Here is a variation, not very original looking.  I
have long promoted  real temp gauge, later with EFI
fuel pressure and Wide Band OX sensor gauges can
help monitor things. 

The 79 Eldo here has had a WBOX gauge for a couple
dozen years.  Since it does not have cruise control,
I mounted the pressure and temp gauges in the switch
position.  The connections for gauge power and light
were nearby on the rear defog switch, so I just extended
a small cable over to the new gauges, with a connector
for service removal.  Temp is a gas bulb needing no
power, fuel pressure uses a solid state sensor T'd
onto the fuel rail, no fuel line or mechanical sensor
to wear out.  Bruce Roe

79TmFP.jpg