My wife has a 2004 Grand Prix. The fan stays running when the car isn’t running. We had to unplug it. How can I tell if the resistor is bad? I was told it was the resistor or the switch.
A bad resistor (likely there are at least three of them) will not cause the fan to stay running. They are only used to provide speeds other than high. Assuming you are talking about the cabin fan and not the engine fan, the only cause I can think of is a bad switch, or in newer cars, it might be a computer error.
Are you sure you mean the blower motor fan, the one inside the cabin, and not the engine fan? The blower motor fan is typically ignition-switched, while the engine fan in many cars is programmed under certain conditions to run even without the key in the ignition. Does the problem exist even without the key? Please clarify.
The high blower relay is included in the resistor assembly which would be your most likely culprit. The next time this happens remove 30 amp fuse in underhood fuse block labelled something like “Batt main 4” and see if it stops. If so I would take this as an indication of a bad relay in the resistor pack.
It’s not the engine fan and it happens with the key out.
It’s the heater fan.
There are kits (supplied by GM) called “afterblow” kits. The idea is to keep the blower running for up to 20 mins after engine shutdown in an effort to dry out the evaporator so as to reduce the chance for bacteria (and the odor associated with it) from forming. I ask have you had the car long enouch to say this is not the effect from a afterblow kit? will the blower eventualy stop on its own after a period of time, if yes, how long is this time period?
Just changed the resistor. Working fine now.