'56 Coupe Deville project

[Cadman-iac]

Rick,

The specific resistance wire you are referring is called “Nichrome” it is the type used on both the inside A/C temp control lever and the thermostat on the evaporator unit. I believe the insulation used on the thermostat wire was cotton.

There should be two wires coiled around the capillary tube one has a few turns while the other has about twice as many. The short one would have a resistance of about 15ohm with a length of +/-15” and the long would be about 45ohm with a length of +/-32”. Both ends are strapped at the end of the capillary tube for the ground, DO NOT solder them at the end of the capillary tube you will destroy the tube.

The smaller wire heater is controlled by the inside temp lever position to open or close the thermostat for the compressor cycling. When the control is place on the full “cool” position the larger one is place in-line for a longer cycling.

Mine was bad so I had to modify it with a newer Ranco unit and built the heater coils and transplant the contacts over. I used a fiberglass sleeves to isolate the wires around the tube they were thing and did allowed heating around the tube.

HTH

Thanks for clarifying that Jose. I appreciate the help.  Let me ask you this though,  where do you get that wire at? What's more, what about the cotton insulation? Or any insulation that's small enough for the wire? If I use something that's too big or too thick it won't right. I think the heat wouldn't reach the tube.
And yes, the wire on mine was crimped under that small cap on the end of the tube for a ground.  I could see the solder on it too.
I had 3 of these control sensors to begin with,  but I knew at least one was no good as the mice had chewed up the wires everywhere.
While experimenting with this one, I found out the hard way that if you try to unsolder the original wires and replace them,  then the tube is rendered useless.  As the sudden flare from the end of tube in the solder made evident. (One down,  two to go). I won't be trying that again!
My thought was that the insulation was probably something like asbestos because of the heat involved. I could see scorch marks on the old stuff and figured that cotton would be really easy to light on fire.

[Cadman-iac]

R12 isn't that badly priced and there's tons of it on eBay and Craigslist.  I'd rather pay extra to run R12 and have it COLD than run R134 and have it _cool.

Dan, true, the R134 isn't as effective as R12, but I've had good luck converting my other vehicles over to 134.
One thing I learned is not to charge the system with as much as the conversion charts say to do.
The R134 seems to work better when it's under charged just slightly.
Now I'm not sure about that with this original Cadillac system. I'm going to use an A6 compressor though,  resealed with all new components, and a condenser and a (new) dryer from a '72 Cadillac. The newer condenser design (and larger), should be be better than the original one is. ( I had to laugh when I first picked up the original one.  No wonder these cars got lousy fuel mileage !!  It's all steel !!).
It's the size of the system that has me wondering.  That's an awful lot of refrigerant even for an R12 system.
There's a big chance that there will be a leak somewhere regardless of the preparations and precautions I would take. Just too many connections,  and using the  original equipment for most of the system,  I'd be more comfortable trying it with R134.

[J. Gomez]

Thanks for clarifying that Jose. I appreciate the help.  Let me ask you this though,  where do you get that wire at? What's more, what about the cotton insulation? Or any insulation that's small enough for the wire? If I use something that's too big or too thick it won't right. I think the heat wouldn't reach the tube.

I got the resistance wire and the insulation sleeves from different sellers on eBay. I believe the sleeve I’ve used are fiberglass they do allow head to go out as I’ve tested them with the wire before winding the wire around the tube and where the perfect width for the wire.

It has been a few eons ago and can’t remember where I stashed the left over ones. Memory capacity for storage is very low. 

The resistance wire came in different sizes so I had multiple uses for them beside the A/C thermostat, I’ve also use the large size to remake the headlight switch rheostat coil.

My thought was that the insulation was probably something like asbestos because of the heat involved. I could see scorch marks on the old stuff and figured that cotton would be really easy to light on fire.

It may well be asbestos not 100% sure at that time it look more like cotton after 60 years but with age things tend to look different.   

[Cadman-iac]

I got the resistance wire and the insulation sleeves from different sellers on eBay. I believe the sleeve I’ve used are fiberglass they do allow head to go out as I’ve tested them with the wire before winding the wire around the tube and where the perfect width for the wire.

It has been a few eons ago and can’t remember where I stashed the left over ones. Memory capacity for storage is very low. 

The resistance wire came in different sizes so I had multiple uses for them beside the A/C thermostat, I’ve also use the large size to remake the headlight switch rheostat coil.

It may well be asbestos not 100% sure at that time it look more like cotton after 60 years but with age things tend to look different.   

Thanks, that's good to know.  I'll look into it on the web then. I had checked with the local electronics supply store with no luck.

Let me ask you this then. Would the system work without the resistance wire, just use a resistor instead to get the load on the circuit,  and then just let the tube handle the temperature fluctuations on it's own?
I'm assuming that there needs to be a small load on the control panel instead of going straight to a ground at the sensor.
And would you happen to know what the amperage is on both of these circuits?
My guess is that it's not gonna be very much at all or the A/C control would fry.
The heavy amperage from the compressor clutch is handled by the cycling switch in  the  evap case if I remember.
I'm just trying to figure out if there might be a way to eliminate this resistance wire but still maintain the original control system.

Also. I'm gonna guess the system won't work with the resistance  eliminated completely.  There must be some sort of resistance here right?
I'm asking all of this looking for an alternative to the resistance wire, since it is such a pain to replace. 

And I understand completely about the limited storage space in the memory banks.  I too have this problem.
I usually learn something new every day,  however I alleviate it by forgetting twice as much every day.  I think that in about another 10 to 15 years I should be a complete blithering idiot! (Although some people think that of me now!) LOL

Have a good day Jose, and thanks for your time and help.

[J. Gomez]

Rick,

The resistance wire is needed to control the thermostat to cycle the compressor, when heat is generated to warm the capillary tube the thermostat will close the +12V path to the compressor to turn it on. When the cold temp inside reaches the set temp per the adjustment setting at the thermostat adjustment screw it then opens the path to the compressor to turn it off.

The thermostat is similar as the one used on freezers except it works in reversed order to cycle the compressor.

If you set the inside A/C controls to full cold the cycle last longer keeping the compressor “on” longer, since the longer heating wire at the thermostat would take a bit long to head up.

You also have a second thermostat which is inside the evaporator with the capillary going around the cooling line low side (from memory) this is the freezer control, this will open the path to the compressor if freeze develops around the lines.

HTH

[Cadman-iac]

Rick,

The resistance wire is needed to control the thermostat to cycle the compressor, when heat is generated to warm the capillary tube the thermostat will close the +12V path to the compressor to turn it on. When the cold temp inside reaches the set temp per the adjustment setting at the thermostat adjustment screw it then opens the path to the compressor to turn it off.

The thermostat is similar as the one used on freezers except it works in reversed order to cycle the compressor.

If you set the inside A/C controls to full cold the cycle last longer keeping the compressor “on” longer, since the longer heating wire at the thermostat would take a bit long to head up.

You also have a second thermostat which is inside the evaporator with the capillary going around the cooling line low side (from memory) this is the freezer control, this will open the path to the compressor if freeze develops around the lines.

HTH

Hey Jose,
Yes I figured the sensor in the  evaporator case/core cut power when it got too cold.
I think I got the resistance wire function backwards though.  I was thinking that the short wire didn't get as hot as the longer one.
But as for the actual purpose of the resistance wire, isn't it  there to keep the tube from switching the sensor off/on before the air temp gets too cold? At least that's the way I understood it to work,  but like I said before,  I'm no electrician, that's why I'm asking these questions.

I'm glad you're taking the time to answer them. I thank you too.
Rick

[James Landi]

James,
Yours must have been a 4 door sedan if the ac came out overhead.  I wish that GM had done that for all models. When I first got mine I thought someone had modified it because the ac vents were only on each side of the rear package shelf.
I found a set of the clear tube/ducts for it before I realized that the hardtop models didn't use any.
I would think it's more effective if it comes out in the roof.
I gotta wonder how much of the cool air will reach the front seat from flat vents on the rear shelf.
Another thing I'm wondering about is why the  control for the outside air intake is mounted on the rear package shelf where it can't be reached by the driver.
It seems like the engineers didn't think this through very well.
Nonetheless,  I'm excited to see how it works when I get it done.
I'm kicking around the idea of converting it from R12 to R134 because of the availability of the R12 and the outrageous price for it if you can even find it.

Thanks for your comments and memories on it. Much appreciated.


Rick

Getting back to your comments about the effectiveness of the "ceiling mount" a/c diverters in the SDV, as I mentioned, the a/c was "bellissimo"   --- with sufficient cooling to create condensate that would drip on my neck and shoulder, and often fog up part of the side windows.   Much like a/c in an modern jet liner, that system would cool down the car in three minutes time.  Also, in spite of the cold air running through those plexiglass tube in the rear, they never fogged up --- the a/c was amazing.   James

[J. Gomez]

Hey Jose,
Yes I figured the sensor in the  evaporator case/core cut power when it got too cold.
I think I got the resistance wire function backwards though.  I was thinking that the short wire didn't get as hot as the longer one.
But as for the actual purpose of the resistance wire, isn't it  there to keep the tube from switching the sensor off/on before the air temp gets too cold? At least that's the way I understood it to work,  but like I said before,  I'm no electrician, that's why I'm asking these questions.

I'm glad you're taking the time to answer them. I thank you too.
Rick

Rick,

Yes is a bit complex verbally explaining the function of the thermostat, it took me a while to understand the logic on its operation when I was working on it.

If you have the service manual under section 16 page 16-A-3 Fig 16-A-4 show the operation of the contacts on the thermostat.

The short resistance wire work in series with the A/C temp control rheostat, so if you move the lever to “cooler” area you will add additional resistance from the control rheostat causing the resistance wire to take longer to warm up. When you slide the lever over to the opposite side you will be decreasing the resistance causing the resistance wire to warm faster as the control moves lower.

HTH

[Cadman-iac]

Ok, that helps out.  If I'm getting this right then,  the control won't work without the resistance provided by the sensor?

What if you were to replace the nichrome wire with an actual resistor of the same value?

Just thinking out loud here, so to speak.
So the only purpose of the rheostat on the control is to provide a variable voltage to the resistance wire on the sensor, thus controlling the temperature. 

The resistance wire heats, or not, the capillary tube. The tube, being sensitive to air temperature,  expands and contracts the bulb moving--- what? So what does that sensor actuate? Just an on/off switch for the other sensor that's in the middle of the evaporator core which cycles the compressor, or have I got it all wrong again?

Is there any way to bypass, or eliminate this resistance sensor from the circuit, or perhaps a newer type of sensor?

I'm wondering how long would this original one work even if it was intact. It's not the easiest thing to remove given its location, and to rewire it isn't going to be easy either.

I looked up the nichrome wire,  and there's some available in many sizes, the smallest being I think 34 GA. not sure yet just what size mine is,  gotta get up off my backside and go look.
The temperature rating on this stuff is really high, upwards of 2500 degrees.
Just how hot does this resistance wire on the sensor actually get,  do you know? If it got that hot, I would think it would melt the solder.
But back to the wire insulation,  I think I had tried to determine what it was once by trying to burn a small piece of it. When it didn't go up in flames, I assumed it was asbestos.
I looked for the fiberglass wire cover.  I found it, but it didn't seem like it would be able to tighten up on the wire enough.  How big was the stuff that you got? And where did you find it?

Once again,  I want to thank you for your time and help. I'm very grateful to you for trying to educate me.
Rick

[Cadman-iac]

Ok, I just thought about the cycling switch swap idea, but that doesn't work because the newer cars that use it also use the mix door to blend the hot and cold air to get anywhere in between.
Now the'88 Brougham I had,  had a capillary tube sensor on the low pressure line before it entered the evap case, but I can't recall if it also had a low pressure switch on the accumulator as well. Even so, I guess that it wouldn't matter,  they still used the mix door to blend the air.
Just brainstorming here. ( I'm getting all wet!!!).
There's gotta be a way to rewire it so that the old sensor isn't required.
Without it, basically all you'd have is an ON, or OFF, no in between.
Any ideas?

[Cadman-iac]

So other than the expansion valve,  a POA valve,  a VIR valve, or an Orfice tube/low pressure switch with a mix/blend door, what other types of control systems are there?

I remember that the old under dash air conditioning used an adjustable capillary tube style switch to control the air temperature by cycling the compressor. Simple, basic, effective.
That's not gonna work for this though, I don't think they make a tube long enough to reach from the evaporator to the control panel.

[Cadman-iac]

Ok, Jose,
I just looked again at the other sensors I have,  and I tested a small fiber from the resistance wire insulation to see if it would burn.  My thinking was if it was asbestos it would not. Well, it burned. So maybe it is cotton after all.
I thought that cotton would catch fire much easier than asbestos would and in this high temperature application they would have used asbestos. But that's just me. Again,  I'm no engineer.

  I also looked at what I have tried for a replacement wire to make the sensor work again.  I've tried some wire from a couple of different old soldering irons,  as well as some from an electric fence cord.
None of them would work though.  Wrong resistance,  or too thick.
To insulate the wire,  I also tried dipping it into a can of plasti-dip. But it's too inconsistent and far too difficult, not to mention too messy.
I'll post a picture of what I have,  some of my notes,  the wire, sensors.

Another question I have is do you know what they used to put over the wire where it's wrapped around the base of the tube? It almost looks like some kind of ceramic or a putty that gets hard. I know that it's there to concentrate and retain the heat on the tube and bulb.

I was just comparing the tube/bulb unit to one out of an aftermarket under dash air unit one. The tube length is the same,  but I need to take the under dash sensor apart to compare the bulb ends. If they are the same,  I can repair the third original sensor I ruined when I tried to unsolder the resistance wire.

I had put all this stuff away for a while to clear my head. Sometimes it helps to take a break from it and just do something else for a while until you can think clearly again.

[Cadman-iac]

Off the subject of the A/C, here's a picture of some of my parts that I've put up after restoring them, the ones that would fit into a box that is. I've been doing  both the ones I'm going to use and any spares I have. This way if I ever do need a part, and it's something I have,  it's all ready to install.


The ones marked with "SP" are the spare parts,  "CDV" of course is for the Coupe Deville.

[gene harl]

FREE  ,,,,  i  have a   package tray A/C  that i removed  from a 59 coupe ,, it's  free if some one  want's to come and get it or pay for the ride..from Fallon Nv.   60miles east of Reno,,,,
     Gene Harl    CLC22406       775-423-8568

[Cadman-iac]

FREE  ,,,,  i  have a   package tray A/C  that i removed  from a 59 coupe ,, it's  free if some one  want's to come and get it or pay for the ride..from Fallon Nv.   60miles east of Reno,,,,
     Gene Harl    CLC22406       775-423-8568

If you'd have said something a week ago I'd have picked it up. My son was in the area for the Parker 500 race.
Damn the luck! I'm here 10 miles north of the Mexico border.
Let me ask you this though,  does it look like the picture I posted here? Just curious now.
Rick

[J. Gomez]

Rick,

If you do a search on eBay under “JELLIFF RESISTANCE WIRE” I’ve found a few sellers with what seems to have the correct wire already wrap with silk. Now that could well be silk what the old wire was wrap with but

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=JELLIFF+RESISTANCE+WIRE&_sacat=0

You may have notice the way the attached these wires was by possible spot-welded them  at the contact side and if I recall via a collar at the tube end.

With the one I refurbished I did not wanted to use any heat around the tube first the nichrome wire WON’T take solder and second as you know ruin the tube with heat. I instead wrap the ends with a few turns of solid hook-up 20AWG wire and used a bit of solder around the wraps careful in isolating the tube from any heat.

To attached the ends at the brass contact terminal I just cut a small grove and wrap the resistance wire around, I use all metal solder to cover the wire inside the grove.

HTH

[Cadman-iac]

Yes, I did notice how they connected the wire. The contact or connector ends had a cut or slice in them, like what you did, then they crimped it in place.
On the tube end, they slipped a sleeve over the end of the tube with the wire under it and then soldered it in place.
I did manage to remove the sleeve from the second sensor tube without any problems. I just used less heat.  On the first one I tried,  I didn't realize that the tube was soldered shut on the end, so I probably used too much heat, as evident in the small flare I got out of the end of the tube when the solder cut loose.

I was just looking at the tube on an aftermarket sensor,  and other than not having the small shielding for the wire to wrap around,  it's identical.  I'll have to reshape the tube to get the coil end on it, but I think it will work out fine.
Not that it will matter if I can't get the wire correct.

As for the wire,  is that guy only selling a 3 foot section for $2 or is that for the whole roll?  The silk cover would probably be fine I think. But I don't have anything silk to do a comparison on for the fire test.

The other thing is the size of the wire. The original wire was only   .006 thousands thick, which measures out to a 34  AWG wire.
The wire for sale you're referring to is  .0195" in diameter,  which is around 24 AWG. I don't know if this will be too big or not, but maybe it would last longer than the original one would.
Do you remember the size of wire you used on your sensor?

I'm sorry for all the questions, but I'm very grateful for your help on this. My thanks again. You've been a big help.

Rick

[Cadman-iac]

  Jose, or someone else with knowledge about these A/C systems, I have a question and an idea to run by you,

So the resistance wire is only there to cause the capillary tube to react faster to the changes in the incoming air temperature,  and make the sensor act basically as a cycling switch.
If the resistance wire is not working, (broken or burned out), then the capillary tube is much slower to react. 
Also, without the resistance wire working,  that takes the "variability" out of the control on the dash.  It's just turned into an ON or OFF switch,  more or less,  right?

What if you were to replace the air temperature sensor/capillary tube/resistance wire sensor/switch unit,  with one from an under dash unit. A capillary tube temperature sensor that's adjustable.
It would have to be adjusted by one of two ways. Either by a knob on the  rear package shelf just like the outside air control is, or, by means of a cable from the A/C control head itself.
This would eliminate the original sensor with a questionable dependability and no availability,  with one that is still available and has less to malfunction.
I would have to figure out how to make it work with a cable. 
But what do you think about that idea?

[J. Gomez]

Rick,

As for the wire,  is that guy only selling a 3 foot section for $2 or is that for the whole roll?  The silk cover would probably be fine I think. But I don't have anything silk to do a comparison on for the fire test.

The other thing is the size of the wire. The original wire was only   .006 thousands thick, which measures out to a 34  AWG wire.
The wire for sale you're referring to is  .0195" in diameter,  which is around 24 AWG. I don't know if this will be too big or not, but maybe it would last longer than the original one would.
Do you remember the size of wire you used on your sensor?

I’ve lost several files when my H/D crashed a few years back, unfortunately some of the details I had from my A/C work is lost.   

The seller has a .0075 wire which probably could be used for this application with a bit longer length to get close to the original wire resistance.

https://www.ebay.com/itm/C-O-JELLIFF-RESISTANCE-WIRE-SIZE-0075/291056178739?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

So the resistance wire is only there to cause the capillary tube to react faster to the changes in the incoming air temperature,  and make the sensor act basically as a cycling switch.
If the resistance wire is not working, (broken or burned out), then the capillary tube is much slower to react. 
Also, without the resistance wire working,  that takes the "variability" out of the control on the dash.  It's just turned into an ON or OFF switch,  more or less,  right?

I would speculate that to be true depending on which side is “open” the longer or the shorter one.

What if you were to replace the air temperature sensor/capillary tube/resistance wire sensor/switch unit,  with one from an under dash unit. A capillary tube temperature sensor that's adjustable.
It would have to be adjusted by one of two ways. Either by a knob on the  rear package shelf just like the outside air control is, or, by means of a cable from the A/C control head itself.
This would eliminate the original sensor with a questionable dependability and no availability,  with one that is still available and has less to malfunction.
I would have to figure out how to make it work with a cable. 
But what do you think about that idea?

I recall that you may be looking at replacing the original A5 compressor with a later type A6 and possible going with an under-dash unit instead of having the rear unit. If you are considering in going this route there are units available today to retrofit or maybe adapting an older unit.

The thing is, you will be the driver that would need to enjoy the cool air not the empty rear area.   

I’m not familiar with how the temp control works on those so I can’t give you any feedback. Or if there is a way to retrofit what is on the older Frigidaire units to replace the temp controls, sorry.. 

[Cadman-iac]

Jose,

I'm still trying to find a way to go with the original air, and with the original sensor.
What I'm have trouble with is finding a wire covering that is small enough and has the right heat protection.
I was looking on McMaster's and they have some that's small enough but I'm afraid it will melt.
They also have some that will hold up to the heat, but it's too big.

As for the under dash air,  I'm not going that route.  I want to keep the original ac.
What I was thinking briefly was maybe using a thermostat from an under dash air that doesn't need the resistance wire to work.  The only problem with this is being able to control it from the dash. It would have to be by a  cable,  or,  the knob put on the package shelf beside the  fresh air intake control.
Neither idea is very good,  I was just thinking out loud again, so to speak.

If I may ask,  how or where did you find out what the total resistance is supposed to be on the sensor? I couldn't find anything about the sensor in the  FSM other than the wiring diagram and a brief description of its function.

Rick