Heater fan switch not working

[73c20jim]

Heater fuse was bad, replaced - upper upper, right right corner of fuse box.

New fan switch.

It works on off - low low fan - no problem like it's supposed to.

Car running, will not adjust fan.

Help, please.

 

[Charlie]

Not sure if my previous issue is related to yours, but, check it out. May be related to the fuse.

https://www.gmsquarebody.com/threads/ac-heater-blower-motor-does-not-work-on-high.26939/#post-513945

I also found out how to disable the lowest blower motor speed. I now have off, med1, med2, hi. Let me know if you want to do that and I will give you instructions.

 

[Mobius]

With the car running, does it only run on high? If so, your blower motor resistor is bad. It’s a five minute fix to replace it.

 

[MikeB]

Are you saying it works on LOW but not on MEDIUM or HIGH?

 

[73c20jim]

Are you saying it works on LOW but not on MEDIUM or HIGH?

Yes.

 

[Matt69olds]

You may have multiple problems. The lower speeds are powered from the fester fuse, to the fan switch, they the various heater resistors, to the high blower relay thru a set of normally closed relay contacts, then to the fan motor. The high speed bypasses the blower resistor, the fan switch on high triggers the high blower relay do a different set of contacts and supplies direct battery voltage to the blower moter thru a separate fuse or fusible link. Put a test light on the blower motor power wire, see if you lose power on the other switch fan positions. Then do the same test on the resistor block. Hopefully you find one or more resistor block contacts that loses power. Then check for power at each blower switch wire. You should see one that has power anytime the key is on, and power at one wire for each speed. If not, the switch is your issue good luck