Just purchased '04 Monte and the heater/air fan is only occasionally running (barely at full setting), it turns on and off if I hit a bump in the road or shut the door. It will run for awhile if I sit still, but if I hit a bump then the fan cuts out, and may not start up until I shut the car off and start it back up (and shut the door) Any help? Thank you!

 

If you haven't already fixed this, it sounds like you need a new blower motor resistor module. They're easy to check before you replace.