Author Topic: 76 Deveille Blows max Hot  (Read 304 times)

Offline 76couper

  • Posts: 3
  • Name: WDP
76 Deveille Blows max Hot
« on: June 08, 2017, 04:29:37 AM »
Hello my friends, I have a 76 Cadillac Coupe Deville. I recently had new dash speakers installed and the In Car climate sensor was disconnected when the dash pad was removed. After the car was reassembled, my car blows maximum hot and the speed at which it blows hot varies with the car speed. The manual says that this is caused by in car sensor not working. I read on a forum post, which I can't seem to find now, that it may not have been reconnected. I can look through my glove box and see the sensor and the connector and it is connected. However, it looks like there is nothing preventing me from flipping the connector around. My question is, can that pose a problem? Meaning could it be that the connector is flipped? I can see the connector but can't reach it so if that's the problem, I would have to remove the dash pad again and I wanted to confirm if that could be the problem before I do removed the dashpad..

Offline Scot Minesinger

  • Posts: 4223
    • CLC Member
      CLC Member #20543
Re: 76 Deveille Blows max Hot
« Reply #1 on: June 08, 2017, 07:13:26 AM »
Not sure if the sensor connector was flipped if it would matter, generally connectors that do matter are made so it cannot be connected wrong.  Since it is a resistor it seems that it would not matter, but you never know.  Get your multimeter out and your shop manual.  A multi meter reads at a minimum volts and resistance in ohms, and they are sold at HD, but best to buy a good one like Fluke on line for about $100 (they are sold as cheap as $20 but you get what you pay for).  Anyway with dash in place, and accessing both wires from under dash by removing connector that you can get to, measure the resistance in ohms with your multi meter and it should be consistent with shop manual.  I think you have to read all three in series, but that should be OK.  As I remember the readings may be around 200 ohms for all three and varies with temp which is what controls the system (tells it to either heat or cool, hi or low).  If the sensor was connected not properly (open) your ohms reading will be infinity, and if it is accidentally grounded (screw thru wire - has happened to me), then it will read very low or zero.  Infinite reading or near zero reading will cause system to go into an extreme either high heat or high cooling in auto, because the system thinks it is past 100'F or below zero due to extreme resistance readings.

BTW, I had a 72 Eldorado convertible climate control and many other issues to repair after the audio shop installed a new set of speakers and radio.  The way they removed the dash was to lower the top and use a back hoe to grab the dash pad and pull it out (not really, but seemed like it with all the broken tabs).  They are typically very sloppy and although the front desk may seem professional you would cry if you saw them work in the back.  Several of the two dozen Cadillac Climate control repairs I have completed are due to audio work.  You are smart to jump on this.  I would normally write to take it back to the offending shop, but it will only be worse if you do.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Offline cadillactim

  • Cadillac Tim
  • Posts: 591
Re: 76 Deveille Blows max Hot
« Reply #2 on: June 08, 2017, 08:38:42 AM »
If everything worked fine before the dash was removed, I would definitely check out that sensor. Maybe the sensor got broken during removal/reassembly (though that would be unlikely). But even though the wires may seem to be connected, there may be a loose connection. A unplugged sensor will cause the system to stay at full heat. As Scott said, this causes an infinite resistance which tells the programmer that it is very cold in the car, needing heat.

Tim
Tim Groves

Offline Gene Beaird

  • Posts: 1015
  • Name: Gene Beaird
Re: 76 Deveille Blows max Hot
« Reply #3 on: June 08, 2017, 03:14:29 PM »
Definitely get the dash pad off so you can chase the sensor wiring.  Perhaps the guy who did the speaker install utilized the 'spare' wire on that thing for his speaker hookups.   :o

Additionally, there's a vacuum hose that runs from the engine bay, through the firewall into the interior to operate the climate controller and vent doors.  I think that if this hose gets knocked loose, the system will also 'fail safe' and go full hot, with all the air through the defroster vents, so while you have the dash pad off, look for this vacuum hose. 

I think that hose entered the firewall on our Seville just to the passenger side of center.  Not sure where it's routed on the Deville, but I'd start there. 

Good luck!
Gene Beaird,
1968 Calais
1979 Seville
Pearland, Texas
CLC Member No. 29873

Offline cadillactim

  • Cadillac Tim
  • Posts: 591
Re: 76 Deveille Blows max Hot
« Reply #4 on: June 08, 2017, 07:44:49 PM »
Gene

The 71-74 programmers default to full heat, but the 75-80 programmers default to full a/c. Different type of transducer used.

Tim
Tim Groves

Offline 76couper

  • Posts: 3
  • Name: WDP
Re: 76 Deveille Blows max Hot
« Reply #5 on: June 22, 2017, 10:38:14 PM »
Thank you all for the replies. I contacted the guy who installed the speakers and he was very familiar with the sensor and was aware that if the sensor got damaged, the car would go full heat. I have another sensor and he is going to take care of it but I definitely want to try the resistor measurement first. Dave