07-20-10, 07:53 PM
I have a '03 DHS and the blower fan will turn on all by itself with the engine off and the key out but only if I leave the a/c on when i get out. Now I thought it might be either the blower resistor or blower relay but I can't seem to find them I did find the bcm or dashboard intergration module mounted behind the glove box and thought maybe it does the job of both the resistor and relay. If anyone has any info please let me know.
Your HVAC system "might have" what GM calls "afterblow" enabled in the HVAC controller. Afterblow can be enabled to move air over the evaporator to reduce the growth of fungus in damp areas. A dealer can enable or disable afterblow with a Tech II tool; the instructions are in the Service Manual.
You will not find a relay or a resistor bank for speed control. Modern systems use pulse width modulation to control blower speed.
07-21-10, 04:29 PM
Do you think this is something that would likely be disabled for a car that would be sold in Florida because of the higher humidity and would it likely run long enough possibly to kill the battery?
Do you think this is something that would likely be disabled for a car that would be sold in Florida because of the higher humidity
All I can offer is an explanation of the options. There is no way I can know if your afterblow is enabled or not.
....and would it likely run long enough possibly to kill the battery?
I believe the maximum run time for afterblow is in the two minute time frame. Certainly not long enough to kill a battery that is not otherwise failing due to age.
It was probably enabled not disabled because the car was in Florida! Again, the fan comes on after shut down to blow air over the evap core to help stop the formation of mold on the surface of the evaporator. ( a normal function ) Also alot of people set the temp display to 60 in the summer which effectively shuts down any incoming air thru the cowl speeding up the formation of mold/ mildew. Imagine closing the door to the bathroom and not turning on the exhaust fan while showering, mold/ mildew form on the walls if done long enough. MAX A/C or 60 degrees displayed has much the effect in a car. So, to wrap up, sounds like your car is normal.