Question: My 1998 Pontiac Grand Prix GTP's CJ2 Digital Heater - A/C Control is putting out only 0.03 volts at pin C11 when the CJ2 connector is back probed and the defroster is set to high. I have performed the air conditioning diagnostics ("Blower Motor Inoperative at Any Speed," pages. 1-186 and 1-187) several times always reaching the final step, # 29, which is to replace the Heater - A/C Control.

I replaced Heater - A/C Control with two different units - both represented as good - and still only 0.03 volts at C11 where the factory specification is 0.5 to 7.0 volts. All three Heater - A/C control units function correctly in all other respects and in the diagnostic mode position 00 is 00. I'm desperate and hope you can help me with a problem that has bedeviled me for months. Thank you, Joe.

Answer: "Back probing" indicates you are doing the test at terminal 11 with it and the blower control module (resistor) plugged in. If this is correct, you are doing it wrong. You need to do it at the blower module terminal C and ground with control head plugged in, but blower module disconnected.

Heater Fan Wont Shut Off

2004 Grand Prix fan for heater doesn't turn off when key is turned off! Please help, what part do I ask for?

Answer: This is a common problem of a burned blower motor resistor. What happens is that the resistor burns, contact is made between different circuits and keeps the fan on. The blower resistor is located under the passenger side of the dash. It has 2 or 3 screws holding it in. That electrical connector may be burned as well. If so, it will have to be replaced too.

Blower motor and resistor location.

Blower Only High Speed

1999 Pontiac Grand Prix heater blower only working on high? Lower speeds of fan not working at all.

Answer: This is another example of a bad blower motor resistor. When they burn up, you can loose some or all speeds.