Car wiring question

My heater fan blower motor is stuck on high speed only. I know there is other speed likes low and medium which is indicated in the dash controls but it remained on high speed regardless of the position of the control knob. I really want these features to work because sometimes, it really gets so hot inside the car. Checking with a friend mechanic, I was told there is a resistor or relay associated with this. Can you send me some info with this problem?

Vehicle wiring advice

Yes, the relay and a resistor are a part of the blower circuit to control the fan speed. The blower motor relay is located on the left center of the engine compartment. The blower resistor is located under the center of the dash. Your fan speed might be caused one of these 3 components:

# Defective blower resistor
# Defective blower fan relay
# Defective blower motor switch located in your dash

The quickest way to check this problem is to check the resistor wirings. The resistor pack is located under the center of the dash near the glove box. It has four wires and if you put the voltmeter test lead on the orange wire, it should change it’s voltage every time you change the setting of the blower motor switch. If not, the resistor is defective which requires replacement of the resistor pack. This part is not expensive and is readily available from GM because it is a common problem.

Notes

The blower fan relay is located at the left center of engine compartment. If the resistor pack does not solve the problem that is your second choice followed by the heater blower switch.

What ever you do when working under the dash panel, do not touch the yellow-taped wiring harness to avoid accidental deployment of the air bag which will activate even with the battery disconnected. Remember: you do this service at your own risk.