Cadillac Repair: 1987 Cadillac Sedan Deville, vehicle speed sensor, cadillac sedan deville

Question
Hi Bill,

I asked you a question earlier this week about this same car I just bought.  The a/c compressor just seized up and the clutch came apart yesterday.  I took the pulley off and installed a shorter belt to run the car without the a/c, but some other problems have arisen with the electrical system.  None of the climate control or fuel control panels lights up at all now and the speedometer is stuck on 85 (pegged).  The heater or defroster will not come on either.  Is this car beyond help?  I just bought it a week ago and have had all of these problems already.  Do I need to take it to a cadillac dealer?  Thanks for any help you can offer.  

Answer
Hi Robert, Sorry I didn't get back to you sooner things have been hectic around here. There doesn't seem to be any reason to have all this happen just because the a/c compressor went bad I would suspect that is why the car was sold in the first place because of the reoccurring problems. The first thing to do with any electrical problem is to check all the fuses that control those componants. You will need a book with complete wiring diagrams for the systems. For the climate and fuel panels what you need to do is unplug one and see if the other lights up. If it does replace the panel that was unplugged. If not then plug that one in and unplug the other. Same senario. Then unplug the a/c programmer. If panels light then the programmer is shorted. The BCM computor is the next step and if you are this far then have a shop double check the diagnosis to make sure you didn't miss something because the computor is $100 or more and a loose wire or bad ground could also cause this. The vehicle speed sensor is on the trans and Cadillac has a specil tool that will duplicate the vss signal to determine if it is a wire sensor or speedo head. The blower motor might have just gone bad. What you need to do is find out how many amps it takes to run the motor and if more than 8A or the meter spikes to 50 A or more starting then replaceing it might get it going again. There is a part called a power module that is mounted on top of the motor housing with 2 wire connectors. Sometimes it has to be replaced along with the motor. If the module isn't sending power to the motor then you should replace both the module and the motor and that might get the air flowing again. If these tests sound strange to you or don't have the propper test equipment then you will need to take it in. Bill