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97 Deville Cadillac No Heat or A/C

frog19972001's Avatar
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01-22-04, 11:05 AM   #1  
97 Deville Cadillac No Heat or A/C

Suddenly I lost the blower and any heat or A/C. Fuses seem OK unless there is an inline one I can't find. In fact, I can't even find where the blower is. I want to check the voltage at the fan if I could only locate it. It's cold out there... any help greatly appreciated. I did pull the diagnostic codes off the dash.. not sure what they mean as it relates to this problem.

codes and my guess on what they represent (not sure is they are accurate)
MSM B0856 Dirty Battery
MSM B1983 Bat/source low voltage
MSM U1300 Class 2 shorted to ground
MSM U1136 Loss of serial communications for class 2 devices
PO 300 ???
PO603 ???

thank you

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davo's Avatar

Join Date: Apr 2002
Posts: 2,417

01-22-04, 03:24 PM   #2  
The blower motor is under the hood on the firewall.If you have a class 2 short to ground my guess is the hvac is the location of the fault but it could be elsewhere.You may have a hard time with this one you will need at the minimum a entire wiring diagram for the car and a tech 2 would be a big bonus.But check for power and ground at the blower maybe you will be lucky and the class 2 fault will be a history code.Also check your battery connections and your grounds on the engine.A alternator output test wouldn't hurt.Keep us posted.

msargent's Avatar

Join Date: Jan 2003
Posts: 469

01-23-04, 06:08 PM   #3  
Many GM cars have done away with the old blower motor resister, and put a blower control module in it's place. These things will cause the symptoms you've talked about.. It's also located under the hood, up near the windshield...

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