Blower motor doesn't turn on - no signal to blower control module?

[Joe942]

The Digital Auto/AC control unit (CJ2) on my 98 GTP isn't putting a signal to the blower speed control wire. I performed the diagnostics in the factory service manual three times and have replaced the auto A/C head unit (twice!) per the diagnostics. There is still no current when I back probe the Auto A/C head unit connector (C11) which drives this wire. All three head units work fine with the exception of putting out a voltage to the gray/black stripe blower speed control wire which goes from the digital Auto/AC control unit to the blower control module. I'm really stuck. Any ideas?

Many many thanks,
Joe

Background: The source of all this was likely a surge from the Electronic Evaporator Dryer (EED) unit which was incorrectly installed by the dealer years ago pursuant to a TSB. The mechanic should have spliced the positive output lead from the EED to the positive blower motor wire instead he connected it to the positive lead going to the blower motor controller. The three wire connector going to the blower motor controller has a burn mark by the 12V+ terminal and there is a burn mark where he spliced into the defroster circuit for 12V+ to power the EED. I've since removed this device and repaired the wiring. The blower motor works find but without a signal to the blower control module no current flows to the wiring which goes to the blower motor.

 

[farmboy73]

I have the exact same problem. I replaced my blower motor about a month and a half ago. Today, drove to work, was blowing warm air just fine. Got in the car to come home, and nothing. The digital unit comes on, fan speed dots raise and lower, but absolutely nothing comes out of the vents and blower motor not engaging. I have checked all the fuses and they are all good. Where do I look now? Many thanks....Todd

 

[Joe942]

Here is the diagnostic procedure from the 1998 Grand Prix Service Manual and the schematic. I'm stuck! I've replaced the original digital climate control head unit (CJ2) with two different used units and still get only a 0.01 to 0.03 v signal from terminal C11 which provides the signal to blower control unit where the factory spec is 0.5 to 7.0 volts. (The circled steps are the ones I used.)