'91 DeVille - fuel data center/HVAC out, blower was on high, now all is ok... ??
 

Hi all,

Yesterday evening I drove my '91 DeVille (84k miles) on some errands. I was out of the car for about an hour and when I got back in, I started it and the fuel data center, nor the HVAC control was lighting up and the HVAC blower turned on high (and I had it turned off when I turned the car off). I turned it (ignition switch) off and on a couple of times and on the third time it lit up and the blower turned off, but it had defaulted to 75° (I had it set on 60°). I drove home 30 miles and it was fine, they all stayed on. When I got home, I turned the car off and on about 4 times and each time they came on. This was the first time that had even happened, however a few weeks ago my HVAC blower came on high by itself while driving and would not shut off. It never happened again. I turned started it this evening and all came on as normal.

I am guessing a short or some sort of module or relay going out?

Any advice on what to check appreciated. The FSM has been no help with this. Someone on another Cadillac site said "BMC"? I think they meant "BCM" (body control module)? I am not sure what that is though, how to check, etc.

I want to be sure that the car does not break down on me - I plan on driving it to work over the next week or two while I have the A/C worked on my Toyota.

Thanks.

I had a similar issue.
 

My climate control and fuel data center got less and less reliable, and eventually would only turn on after 30 minutes to an hour of driving, eventually the neutral safety switch gave me trouble, and after replacing it, the climate control and fuel data center worked perfectly! I’m guessing a signal or ground that effects the BCM is routes through the switch, is replaced the BCM and prom with no effect on the problem.