Fan speed switch?

[gunmunky]

Need the help of smarter than me people!! I have an 03 GMC Sierra and the fan speed switch works fine on 1,2,3,4 but on 5 /high/ it turns off. Is this most likely the switch or something else ? Thanks for any help.

[jeffreyd]

high fan resistor or relay

[gunmunky]

Do I find these in the cab on the passenger side?

[Jeremy airjer W]

Yes, it will be located near the blower motor under the passenger side dash.

The high speed relay and resistor are one unit. You should have power to the orange wire at the resistor with the switch in the high position. This will verify that the switch is working. Check for power on the red wire at the resistor. This is the power from the high speed fuse that is used to power the blower in high speed mode. If there is power there than the resistor is bad.

[gunmunky]

Thanks for the info. Hopefully I can get to it in the next couple of days.