12 Volt conversion of 1941 6219

[28938]

I recently converted my '41 to 12 volts. Can someone give me a part number for the temp gauge sender for the conversion? Mine is showing HOT and the car does not run hot.

[tturley]

My Lasalle was converted to 8 volt and had same issue. I went to a radio supply house and bought an assortment of inline resisters and experimented with different ones until temp gauge matched IR readings.
They are very cheap

[C Gorgas]

I went through the same issue and finally removed gauge and sender...forwarded both to Williamson's Instruments, Chester, Arkansas. Problem solved. They advertise in Hemming's and are reasonable. Chet 25441

[bcroe]

Inserting a resistor might make it read right at the most important normal
operating point.  But it will still be off everywhere else. 

I have built some gauge correction circuits.  But now there is a universal
device available, that you can customize to your situation.  Bruce Roe

adapt between any sending unit and any gauge.

http://www.technoversions.com/MeterMatchHome.html

[35-709]

Neat!  How about posting that over at the MCLC, Bruce.

[bcroe]

Neat!  How about posting that over at the MCLC, Bruce. 

Did somebody ask about this problem?  You can post it.  Bruce

[35-709]

No one asked, I just thought it was a great piece of information to pass on for someone's future reference, a great gizmo --- in my alleged mind.  I have placed your link in my "Favorites" file and will post it over at the MCLC.
Geoff

[bcroe]

No one asked, I just thought it was a great piece of information to pass on for someone's future reference, a great gizmo --- in my alleged mind.  I have placed your link in my "Favorites" file and will post it over at the MCLC.     Geoff   

Yes imagine, a programmable device on a 40s car.  Wondering if it could
work on anything but 12V, negative ground.  I have designed a few gauge
circuits, but now anyone can do it. 

Come to think of it, this device could emulate the 70s EFI temp sensors,
and it costs a lot less.   Hmmm  Bruce Roe

[Glen]

Most newer digital devices run on 5 volts, which would work well on a 6 volt system.   

[bcroe]

Most newer digital devices run on 5 volts, which would
work well on a 6 volt system.   

5V did become a standard logic supply in the 70s.  But to actually use electronics
in the hostile environment of a car, you need a power supply.  That might be as
simple as a reverse polarity diode and a filter, or it might be more complex.  A
common voltage regulator needs a minimum of 2 extra volts (headroom) to
function, with a diode putting you at 8V minimum.  Voltage regulation in cars isn't
great, you could lose more headroom to that. 

These days there are devices using lower voltages like 3V.  If they are used in
the MeterMatch, it might well handle 6V cars.  Use in positive ground could be
handled by reversing the supply lines, but the output meter driver circuit would
need to cover rail-to-rail, bi directional drive.  I'd certainly inquire if MeterMatch
would cover such a situations. 

When I first tried adding electronics to my (7 year old) 62, I found that stuff
working when I shut the engine off, had failed when it was restarted.  The cause
was tracked down to voltage spikes generated by the starter motor.  The arcing
of the commutator generated pulses of up to 300V on the wiring, of both
polarities.  The pulses were extremely short, on the order of a microsecond.   
They were no threat to robust things like 12V bulbs, but the pulses punched
holes in my transistors.  The solution is a power supply designed to tolerate and
keep out such pulses.  This  can be done by devices like TVS diodes and other
means.  More headroom may be used in the process.  Bruce Roe

[Driver8]

Yes imagine, a programmable device on a 40s car.  Wondering if it could
work on anything but 12V, negative ground.  I have designed a few gauge
circuits, but now anyone can do it. 

Come to think of it, this device could emulate the 70s EFI temp sensors,
and it costs a lot less.   Hmmm  Bruce Roe

Bruce, wow, so odd that you mentioned the EFI sensors here just now. This morning while looking up some car stuff online, I thought... maybe I ought to grab 1 or 2 extra EFI sensors to put away for safe keeping (im down to one used spare). then checked 500cid.com and wow... they've now gone up to $130 each + shipping. Yikes. so then thought, next time i talk with Bruce I'd ask if he ever has considered coming up with his own version of these sensors. Then while browsing the forum, come across this an hour later.

BTW, You've brought so much to Cadillac owners globally with your calibrated ECUs & new MAP sensors that keep these old EFI Cadillacs running happy & strong. If not for you, many of us would be forced with zero option, to go to a carb-conversion. I learned about this system and how to maintain it myself because of you. Can never thank you enough for this

You being an electrical engineer understand all of this so well, I certainly do not, but essentially, is it correct in saying that one could somehow install this on the '70s EFI and have an existing old or dead coolant/air-temp sensor still send the proper signal to the ECU so the car starts and runs well cold as if the sensor was still ok? If so, would you need one device for each sensor then?  mark~

[35-709]

"BTW, You've brought so much to Cadillac owners globally with your calibrated ECUs & new MAP sensors that keep these old EFI Cadillacs running happy & strong. If not for you, many of us would be forced with zero option, to go to a carb-conversion. I learned about this system and how to maintain it myself because of you. Can never thank you enough for this "

Agreed!

[bcroe]

Bruce, wow, so odd that you mentioned the EFI sensors here just now. This morning while looking up some car stuff online, I thought... maybe I ought to grab 1 or 2 extra EFI sensors to put away for safe keeping (im down to one used spare). then checked 500cid.com and wow... they've now gone up to $130 each + shipping. Yikes. so then thought, next time i talk with Bruce I'd ask if he ever has considered coming up with his own version of these sensors.

is it correct in saying that one could somehow install this on the '70s EFI and have an existing old or dead coolant/air-temp sensor still send the proper signal to the ECU so the car starts and runs well cold as if the sensor was still ok? If so, would you need one device for each sensor then?  mark

Mark, The good news about the 70s EFI sensors, is that they only add fuel enrichment
when the engine is cold.  Once hot, you can unplug them, they make no difference.  A
bad sensor can't be fixed.  The thought is use a common, cheap sensor.  The issue with
them is their log output curve.  A log sensor with an electronic box could emulate the 70s
sensor.  This would require a multiple point correction curve, which the MeterMatch can
do.  Probably not perfectly, but well enough for cold operation.  Guess you could even
customize it to your engine, the calibration could be complex.  2 units would be required,
with a 12V connection probably off the cold idle air heater circuit.  And a couple of those
round connectors, cut off defective temp sensors?  Where to mount it? 

I see one more problem, the MeterMatch outputs a voltage, but the ECU expects a
resistance.  Those could be interchangeable for one ECU.  But if a different ECU
supplied a somewhat different current, the MeterMatch should output a somewhat
different voltage.  That may NOT be a problem; I could check that all 5 ECU versions
use the identical sensor interface.  I and others petitioned the original mfr and they
are willing to supply sensors for now.  So I haven't pursued another solution, but at
least there may be another one now. 

Another way is to install a small conversion PCB in the ECU.  But this would make
it custom and entirely NOT interchangeable with any other ECU.  I have completely
avoided any solutions of that nature till now.  Bruce Roe