: Electrical Issue



piroguy14
07-11-11, 04:42 AM
I recently purchased a 1979 Coupe DeVille and upon turning the a/c on, the dash began to smoke and I immediately turned the car off. I took the dash, where the radio and a/c control panel is located off and found that the purple wire, on the far right side was partially melted. When the a/c is off everything is fine, as soon as i turn the a/c on the wire heats up. I figure it has to be a short somewhere but i have no idea where to look. I bought a Chiltons manual but it doesn't seem to have any info on where that wire leads. Any help would be amazing i want my a/c to work!!

pompste
07-11-11, 08:49 AM
I recently purchased a 1979 Coupe DeVille and upon turning the a/c on, the dash began to smoke and I immediately turned the car off. I took the dash, where the radio and a/c control panel is located off and found that the purple wire, on the far right side was partially melted. When the a/c is off everything is fine, as soon as i turn the a/c on the wire heats up. I figure it has to be a short somewhere but i have no idea where to look. I bought a Chiltons manual but it doesn't seem to have any info on where that wire leads. Any help would be amazing i want my a/c to work!!

Looks like this is your first post here--welcome to the forum!
Congrats on your '79 Coupe Deville!
First things first--check your A/C fuse under the dash far left corner near the parking brake.Your fuse may be too rated too high since it should have blown the fuse first and not melted the wire.
It could be a short or possibly the A/C compressor is seized up.
Others will chime in soon to offer some helpful info.

csbuckn
07-11-11, 10:15 AM
I believe they were known to have issues with the AC relay. Cant remember where it is but it would always melt.

sven914
07-11-11, 11:05 AM
Get a Factory Service Manual that was used by Cadillac dealerships. They are reasonably priced on eBay; here is a link (http://shop.ebay.com/i.html?_nkw=1979%20Cadillac%20Service%20Manual&_dmpt=Motors_Manuals_Literature&_ds=1&_fcid=1&_localstpos=44641&_sc=1&_sop=15&_stpos=44641&gbr=1). You want one that says "Service Information" on the cover, because they include everything (engine, body, and electrical) for your car.

The Climate Control system used in those cars did kill relays, but that shouldn't cause any melted wiring.

piroguy14
07-11-11, 01:08 PM
Looks like this is your first post here--welcome to the forum!
Congrats on your '79 Coupe Deville!
First things first--check your A/C fuse under the dash far left corner near the parking brake.Your fuse may be too rated too high since it should have blown the fuse first and not melted the wire.
It could be a short or possibly the A/C compressor is seized up.
Others will chime in soon to offer some helpful info.

Thanks for the quick reply! Well i did check the fuses under the dash and it looks like almost everyone one was rated wrong, it seems that someone pulled a bunch of them and put them back in the wrong slots. I switched them around and now im going to go try it again and hopefully this time the fuse will blow out and the wire wont heat up. If that is the case, how would i be able to tell if the compressor has seized is there any tell tale signs?

piroguy14
07-13-11, 06:21 AM
I am now just considering removing the a/c unit and all that stuff all together. I'm not sure what would be involved with that but would it be cheaper/easier to remove it all or to have a mechanic trouble shoot/fix and convert to s-134?

pompste
07-13-11, 08:06 AM
I believe they were known to have issues with the AC relay. Cant remember where it is but it would always melt.

The '77-'79`s had "blower motor relay" problems----design flaw.I know since my '78 Deville had that problem.

pompste
07-13-11, 08:13 AM
Thanks for the quick reply! Well i did check the fuses under the dash and it looks like almost everyone one was rated wrong, it seems that someone pulled a bunch of them and put them back in the wrong slots. I switched them around and now im going to go try it again and hopefully this time the fuse will blow out and the wire wont heat up. If that is the case, how would i be able to tell if the compressor has seized is there any tell tale signs?

If it`s seized up,the front of the compressor that rotates when a/c is turned on would`nt move.

pompste
07-13-11, 08:21 AM
I am now just considering removing the a/c unit and all that stuff all together. I'm not sure what would be involved with that but would it be cheaper/easier to remove it all or to have a mechanic trouble shoot/fix and convert to s-134?

When you say "removing the a/c and all that stuff"---do you mean remove it permanently?
Most auto service shops will do a diagnosis for free--i`d go that route first and get an estimate.
I converted my '78 Deville`s A/C from R-12 TO R-134a myself last year and it works great! But you need a working compressor to do it.Make sure your compressor works or not first.

sven914
07-13-11, 12:30 PM
If you remove the Climate Control, what would you put there? It would be pretty difficult to replace the system with a non-Cadillac unit (not to mention it would look horrible). You could replace it with a digital ECC unit, from an '81-'89 RWD, but you would need a lot of parts and it could get expensive.

The most cost effective thing would be to find out where that purple wire goes. The insulation has probably rubbed off and it's touching metal somewhere, so you should replace it. Then you need to test the component, the wire goes to, for any malfunction or damage.

If there was no problem with the A/C system before the wire melted, there is no reason to exchange the refrigerant. If you do upgrade to 134a, you (technically) should replace the compressor because the 134a molecule is smaller than R-12 and will leak. If you live anywhere that gets hot during the summer, you will notice a lack of performance from the A/C system, because 134a does not cool as well as R-12.

CADforce69
07-13-11, 03:52 PM
My '73 dodge previous owner charged the A/C system with R134 gas, as he proudly told me, with no conversion (5 years ago I did not know it was needed) and at first it cooled very well but when engine was getting hot or I revved up, I got only warm air. I felt like it was shit. As I had to rebuild engine, this time I got R12 and since that day that A/C cools like devil. you canīt stand thermostat at half power; I usually adjust it by 1/4 power.

piroguy14
08-03-11, 03:09 PM
Thanks for the suggestion, I need to find a diagram of where that wire goes, I will probably get the Cadillac service manual for some online source

sven914
08-03-11, 03:54 PM
eBay would be the best place to find for the lowest price.

cadillac_al
08-04-11, 07:16 AM
Doesn't the purple wire go to the blower? Did the blower work when it was on? could be seized up