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Discussion Starter #1 (Edited)
Hello all! I have a 81 Cadillac Eldorado that sat up for 2years with 60k miles on it thats having some issues.

I’m not getting any power from my climate control module,when I first got it the climate control would work sometimes and sometimes it didn’t.

I know it was low on Freon so we were able to Hotwire the compressor to get 2 cans of Freon in it thinking that would make things kick back on.
I took it to the mechanic shop and he said that the hvac control module programmer needs to be replaced.

just wanted to get a 2nd opinion to see if anyone else has had this problem before I spent any unnecessary money.


UPDATE.......

I took the Climate Control head out of the dash (which was surprisingly easy) and I cleaned the connection with a little contact cleaner in hopes that it would power on but that didn’t work.

i am having some issues with the radio to where it won’t play fm/am stations but I noticed that if I give the radio a “love tap”(while it’s out of the dash) and the display lights came on AND it started playing Fm stations.
Any idea what that’s about?
 

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Welcome to the forum,
I don't know the answer to your question but having a service manual and something which shows circuit diagrams can be very helpful. If there's an electrical trouble shooting manual for '81 that normally explains the operation as well as showing the diagram. There is a circuit diagram manual on eBay for $7.95 right now and hard to go wrong having something like that. You may simply have a ground or power/ fuse issue.

Here's the link to the electric diagrams for Eldorado and Seville on eBay:

Good luck,
Scott
 

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1981 Biarritz, V864
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I have an 81 Eldo and have the Cadillac Factory Service Manual for it. I had a look at the ECC section in the Manual and it has some very detailed troubleshooting flow charts and the detailed electrical schematics that they refer to also. There is a lot of interconnected wiring between the Climate Control head, the MPG display, the Climate Control programmer, the ECM, the Range Computer and the Power Module.
If there is no display and no control is the fuse for the Stop/Hazard lights good as it provides the power to the head. Also the fuse for the rear parking lights/license plate lights also feeds the head. If you are mechanically inclined I can send a scan of the wiring diagram but you will need to be a good troubleshooter to follow it. Also replacing the head is not difficult as it comes straight out of the front of the dash once you remove the bezel plate that is in front of it but you will need a replacement that you know works and that is going to have to come from E-bay or a U-pull yard if you can find one. I hate to suggest it but I would also be concerned that you may have blown the power module which controls the A/C compressor clutch and the heater blower motor if you didn't have the wiring disconnected from it when you jumpered the A/C compressor. They are a hard to find item and if you get one that is working they usually are a few $.
I have not had issues with mine but I would be happy to try and help out further so if you need more technical info., just let me know. Dave
 

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Discussion Starter #4
I have an 81 Eldo and have the Cadillac Factory Service Manual for it. I had a look at the ECC section in the Manual and it has some very detailed troubleshooting flow charts and the detailed electrical schematics that they refer to also. There is a lot of interconnected wiring between the Climate Control head, the MPG display, the Climate Control programmer, the ECM, the Range Computer and the Power Module.
If there is no display and no control is the fuse for the Stop/Hazard lights good as it provides the power to the head. Also the fuse for the rear parking lights/license plate lights also feeds the head. If you are mechanically inclined I can send a scan of the wiring diagram but you will need to be a good troubleshooter to follow it. Also replacing the head is not difficult as it comes straight out of the front of the dash once you remove the bezel plate that is in front of it but you will need a replacement that you know works and that is going to have to come from E-bay or a U-pull yard if you can find one. I hate to suggest it but I would also be concerned that you may have blown the power module which controls the A/C compressor clutch and the heater blower motor if you didn't have the wiring disconnected from it when you jumpered the A/C compressor. They are a hard to find item and if you get one that is working they usually are a few $.
I have not had issues with mine but I would be happy to try and help out further so if you need more technical info., just let me know. Dave
Hey man I REALLY do appreciate the advice any little bit helps! I have a mechanic that has been doing all of my work for me on this car but the a/c thing stomped him so that’s why I took it to an actual shop for a diagnostic.
I’d love to check out the scan of your diagram and hopefully we can find a resolve. I did find a climate control head on eBay that I plan to purchase just in case that is the problem
 

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Discussion Starter #5
Welcome to the forum,
I don't know the answer to your question but having a service manual and something which shows circuit diagrams can be very helpful. If there's an electrical trouble shooting manual for '81 that normally explains the operation as well as showing the diagram. There is a circuit diagram manual on eBay for $7.95 right now and hard to go wrong having something like that. You may simply have a ground or power/ fuse issue.

Here's the link to the electric diagrams for Eldorado and Seville on eBay:

Good luck,
Scott
Hey thanks for your reply! I was thinking the same thing that it was a ground or fuse issue. Would you happen to know where the relay for the a/c is located?
 

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I unfortunately don't know the system well. I have a 1979 and I'm not certain it's the same. In addition a lot of my experience comes from my 79 Toronado and that has the semi automatic system. I have both the Eldo and the Toro E-Bodies. Dave who also answered is very helpful. I'm concerned based on what he wrote jumping the compressor may have done some damage. The manuals may provide a method for testing it.

If you have a mechanic helping you I would get him/her the manuals. Most manuals are pretty reasonable. Most factory service manuals have nice diagnostic trees. The circuit diagram I found on eBay for $7.95 was even free shipping! That would almost certainly tell you where the relays are. They will name a junction by a letter and typically a 3 digit code and then describe where it can be found or show it in a diagram.

Scott
 

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1981 Biarritz, V864
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Here is the scan of the circuit diagram, two pages worth. This is for the 368 V864 engine which I have assumed is in yours? If you are buying one off E-bay watch carefully on your purchase as there are slight variations between different years and models and I don't know that they are 100% compatible. The correct PN should be 1224842 or 1224845 if it doesn't have the electric rear window defroster or 1224841 or 1224844 if it does. It indicates in the parts book that the lower number is the 1st design and the higher number is the 2nd design for the 81 E car. Not really sure what the difference is but maybe you should pull yours to have a look at the label (if is still attached). Dave
 

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Dave,
The one I found on eBay is for '81 but I just took as much of a look as I could and it seems like body and chassis only so the one I found, I suspect, may not cover all systems. It looks like one large color fold-out.

Scott
 

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Discussion Starter #10
Here is the scan of the circuit diagram, two pages worth. This is for the 368 V864 engine which I have assumed is in yours? If you are buying one off E-bay watch carefully on your purchase as there are slight variations between different years and models and I don't know that they are 100% compatible. The correct PN should be 1224842 or 1224845 if it doesn't have the electric rear window defroster or 1224841 or 1224844 if it does. It indicates in the parts book that the lower number is the 1st design and the higher number is the 2nd design for the 81 E car. Not really sure what the difference is but maybe you should pull yours to have a look at the label (if is still attached). Dave
Hey thank you so much I really do appreciate the help!! Yes mine is the 368 V864 and it doesn’t have a rear defroster option on the panel but I’ll make sure to pull it before I purchase a replacement.
 

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'84 Eldorado and Seville
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Chances are it is the dash control module. You can usually find a used one on eBay or a salvage yard. If you find a salvage vehicle close by you might get it cheaper than eBay. I pasted in a link to a salvage yard search.

What will cost you around $300 is a rebuilt blower resister control module located on top of the evaporator case with a bunch of wire's connected to it. That controls the A/C compressor cycling and blower motor speed. FYI I would remove the old blower motor and put in a new one.. Sure enough an old motor can burn up that module then you'll be screwed trying to find a rebuilt module. Rock Auto sells new blower motors and other places also. Pretty common GM part.

The other piece to all of this is the programmer module located behind the glove box that controls the vents opening and closing. I think an '81 used that. That has a screw like part that can strip off and not work. Then your vents won't work correctly as in no heat blowing out at the floor and A/C doesn't come out of the dash vents.

 

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1985 Eldorado ASC convertible, HT4100
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Welcome aboard 81. Good advice above. Just to make sure, did you check all the fuses and check/clean the relevant electrical connections behind the dash, in the engine bay, etc.?
 

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Discussion Starter #14
Welcome aboard 81. Good advice above. Just to make sure, did you check all the fuses and check/clean the relevant electrical connections behind the dash, in the engine bay, etc.?
Hey thanks!! We did check the fuses and they were all good but we didn’t clean any connections, I’ll make sure to do that.
I also just ordered Cadillac’s electrical troubleshooting Manuel for their 1981 series so I’ll try whatever else it takes to get it right.
 

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You won't ever regret getting any of the manuals. You can usually find the big one, the Factory Service Manual (the official Cadillac shop manual), cheap on eBay, like $15 shipped.

This new thread might be useful for you: 1984 Eldorado A/C control

by the way, I recently refilled my A/C. We probably have very similar systems. Refrigerant was bone dry. But even so the system ran when I turned on the A/C before refilling.
 

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Discussion Starter #16
You won't ever regret getting any of the manuals. You can usually find the big one, the Factory Service Manual (the official Cadillac shop manual), cheap on eBay, like $15 shipped.

This new thread might be useful for you: 1984 Eldorado A/C control

by the way, I recently refilled my A/C. We probably have very similar systems. Refrigerant was bone dry. But even so the system ran when I turned on the A/C before refilling.
There most definitely is some activity going on with the a/c system, I could feel the heat coming out of the panel and floor vents and also coming from the defrost vents.

I was thinking about just riding it out but I live in Texas where triple digit temperatures seem to be the normal during the summer 😂😂
 

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I've had three 81's. Two of them had HVAC blower module issues that might help you...
1. First one had blower starting /stopping/changing speeds causing dash display issues then finally no
HVAC blower motor module resistor.jpg
burnt area of failed module.jpg
unburnt amber color.jpg
blower! So I removed the HVAC blower motor module resistor and found it burnt out. There was noticable blackening. See photo attachment. The electronics appear to have been sealed in an amber colored epoxy/silicon.
The local junk yard only had a 1980 module that worked but my "cylinder live" display stopped. Eventually found a couple of 81 modules in a giant junk yard in San Jose, California. They both worked fine. So I'm not sure if 1981 had a unque module for that year only?
2.Next was blower motor again starting /stopping etc. This time it was the connections at the module that were dirty/oxidized'
I could see the ground sparking at night with the hood up and the engine running. After a good clean-up with tiny files and dialectric grease everything is happy again. Also cleaned the inner connect of the multi-pin connector.

Here's a photo of the ground (black arrow) and the middle single wire (orange arrow) that were loose and dirty.
The 2nd photo shows the burnt area of the bad module vs the original amber color of the epoxy/silicone sealer.

.....and yeah the junk yard in San Jose had "junkyard dogs" that they released to run free at closing time! They announced over the PA system warning the dogs were coming out in 15 minutes!

Time to go.

King
 

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Discussion Starter #18
I've had three 81's. Two of them had HVAC blower module issues that might help you...
1. First one had blower starting /stopping/changing speeds causing dash display issues then finally no View attachment 595061 View attachment 595066 View attachment 595067 blower! So I removed the HVAC blower motor module resistor and found it burnt out. There was noticable blackening. See photo attachment. The electronics appear to have been sealed in an amber colored epoxy/silicon.
The local junk yard only had a 1980 module that worked but my "cylinder live" display stopped. Eventually found a couple of 81 modules in a giant junk yard in San Jose, California. They both worked fine. So I'm not sure if 1981 had a unque module for that year only?
2.Next was blower motor again starting /stopping etc. This time it was the connections at the module that were dirty/oxidized'
I could see the ground sparking at night with the hood up and the engine running. After a good clean-up with tiny files and dialectric grease everything is happy again. Also cleaned the inner connect of the multi-pin connector.

Here's a photo of the ground (black arrow) and the middle single wire (orange arrow) that were loose and dirty.
The 2nd photo shows the burnt area of the bad module vs the original amber color of the epoxy/silicone sealer.

.....and yeah the junk yard in San Jose had "junkyard dogs" that they released to run free at closing time! They announced over the PA system warning the dogs were coming out in 15 minutes!

Time to go.

King
Lolololol hey man that 15 minute call seems fierce!!! Not worth being chased down by the part patrol 😂😂 🏃🏿 💨 🐕 😂

so did that mower ever cause your climate control head not to power on?
 

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The first burnt module issue began affecting the display controls of the center climate control and upper dash above the radio. Lots of wierd things.....partial numbers then no numbers with the HVAC motor slowing /speeding and eventually nothing.
The module is fairly easy to remove. Just 3 small screws and a large one attaching the ground to the upper center braces and 2 wires to unplug. Then it carefully lifts out. Check for black burnt area and burnt smell. When re-installing the 3 small screws, only snug them, as they are tightening into the plastic HVAC housing.

San Jose had another huge junkyard that was perfect too. Tons of Lakks raised off the ground. No weeds or mud puddles but crushed rock and neat lanes filled with clean Cads.But they charged $5 admission and had daily specials...the day I was there,
Cadillac trumpet horn.JPG
horns were 2 for $15. I snagged a rare long Cad trumpet horn from a 70. They also rented saftey shoes, work socks and tools.
Plus they would remove any part you wanted for a fee with forklifts, cranes and cutting torches delivering it to your trunk. In the parking lot there were food trucks!
Tacos and Bud.....does it get better?

King
 

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Hi King,
Those are some amazing heat sinks. I'm just guessing but I suspect the burnt color isn't necessarily the location of the failure but rather a sign something else failed. I don't know exactly how these work or how to test them but it seems it has a transistor. I wonder if that could have caused an overheat issue as they can act as an amplifier. Maybe someone else will see your photos who is more on the electrical side than I am and can comment. I was just wondering if the originals could be fixed if junk yard sources start to dwindle.

Scott
Edit: Also be careful of the proximity of that horn and your radiator. Rubbing could eventually cause a radiator leak.
 
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