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MIKEVIN_BEGGS, ASE Certified Technician
Category: Car
Satisfied Customers: 162
Experience:  General Motors, Ford, & Mitsubishi Certified technician.
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1993 cadillac: diagnose..sedan deville..the climate control panel

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I am trying to diagnose a digital dash problem on a 1993 cadillac sedan deville. It's all digital. The problem is that the climate control panel, the fuel data panel, and the information panels are blank. The climate control and the fuel data panel both display a "c"...that's it. Disconnect the battery for awhile, reconnect, turn the ignition switch on, and all displays work momentarily and then flicker and go blank again. The radio doesn't work either, except that it does display the time. Blower motor operates always with key on, circulating air through the defrost only. I have not removed the instrument cluster yet. I have checked all fuses and relays underdash and underhood...all appear okay. Cannot do any onboard diagnostics because the climate control center is blank and doesn't operate. Snap On scan indicates no codes, for ecm only. Ecm has been replaced. Checked what I could in the dash...boards in BCM appear okay under magnification. Bought the car this way.
I will do some research on your trouble and get back with you with an answer, Thanks for being a customer of justanswer Dave

Customer: replied 9 years ago.
Yes, the car runs and drives just fine. Everything else works fine too. The readout on the remaining instrument cluster is fine too...speedo, mileage, etc.
Great will be to you soon Dave
Customer: replied 9 years ago.

I will wait for your answer.





Customer: replied 9 years ago.



Was wondering if you found out anything yet.


I working on your problem for sure Dave
Customer: replied 9 years ago.

Thanks Dave. I'll just take another day away from this problem and tackle something the meantime maybe you will come across something of benefit that might lead to a cure.

Customer: replied 9 years ago.


It's been since last Wednesday that I presented my question, and I have not received an answer yet. Is there anyone else you can forward the question to that perhaps might have a clue as to where I should proceed from here with this Cadillac problem? I could take it to a Cadillac dealership for diagnosis, but the reason I presented the question was to avoid the high costs associated in doing that. Please let me know, at least, if you intend to answer the question and in what given time-frame?

Hello, my name is Kevin,


I have been asked to help with your concern.


These vehicles had an issue with coolant or moisture getting into the bcm at the pass side floor board, causing the bcm & both dash units to fry. (all it takes is a drop) .


If you check the heater core box, I'll bet it is damp on the inside.

(look behind the glove box & you will see the programmer (has vacuum lines & elec. connectors) remove the programmer & the heater core cover).

If is damp, this is your cause. 7 times out of 10.




This is the best pic. I could find.



If it is not. then it is one of the three modules. Unfortunately there is no way to test the modules to find out which one ( or combo ) failed.


Be sure that the replacement modules part numbers match ( check your local bone yard & give them the part numbers off each piece ( on the back of each piece there is a part labile) to save yourself a trip)


replace the heater core if the box is damp, the bcm & both dash units no matter what.

be sure to use a gop of dielectric grease at the bcm.


If there are any further questions feel free to ask.


Best of luck,


MIKEVIN_BEGGS, ASE Certified Technician
Category: Car
Satisfied Customers: 162
Experience: General Motors, Ford, & Mitsubishi Certified technician.
MIKEVIN_BEGGS and 4 other Car Specialists are ready to help you
Customer: replied 9 years ago.


Thanks for your me insight as to what to do next. Already have the glovebox out and will check into removing the programmer and core cover next. Now, it looks like it's bcm and module replacement time, regardless. To be sure, I know what the bcm is, but unsure whether or not the climate control panel and fuel data panel are considered the other two "modules" you mentioned. Are these display panels the other two modules?


Correct. the body control module ( bcm ) is located just under the heater box & the other two module are the HVAC ( ac ) control & the data center ( fuel data display ).


Very often what happens, the heater core starts to leak ( from a drip to a streem ) & the coolant will drip onto the bcm plugs & ZAP.


If I can be of further assistance, just give me a type.

Customer: replied 9 years ago.

Hi Keven,

According to books, the ecm is lodged against firewall, which has been replaced, and the bcm, which I had already removed and inspected, sits above the heater box. I removed the a/c controller and removed the heater box cover...dry with no signs of any leaks, while pressurizing the cooling system. Put everything back together and tried the key again...things flashed on and off, then a "6" appeared in both displays, blower running on high again, then the "c" returned in the displays. Shut the key off and now the blower ran for awhile, shut off, then came back on, then shut off. I pulled the maxi-fuse in the engine compartment after that so the battery wouldn't drain in case the blower motor came back on. So, that's where I'm at. Kevin, my thoughts are to just go ahead and start throwing parts at it, but this is like replacing a fuse without knowing what caused the problem. I'm sure you've been there before...sometimes there's just not enough to go on to be sure, and a guess might be the answer (or not).

Since there are no leaks of any kind.


Replace the fuel info center & the hvac control.


I have run into this type of concern many times, but the normal diagnosis is ineffective because you will always get false voltage readings from the dash modules.


Make sure the bone yard will have the bcm in stoke just in case it is needed.