Blower motor switch keeps blowing/shorting out!

[90_K5 Blazer]

Hey guys,

I'm about to pull my hair out on this one.

I replaced my blower motor switch last night for the 2nd time. So I was all excited that today on the way home from work, I would have A/C once again. Well I did, but only for 15 minutes. All of a sudden the fan just kicked off, and cycling the switch through all the speeds yielded nothing!

What in the name of all that is holy could be cause 2 blower motor switches to break in a 2 day period!?

The fan is fine. I have decent electrical knowledge, and after some wire tracing and continuity tests, I know it's not a bad motor.

Any help would be greatly appreciated!

Thanks in advance,

Eric

 

[HarryH3]

Check the a/c blower relay, mounted up on the a/c box under the hood. I've had them fail such that the relay contact was stuck in between the other 2 contacts, sending no power to the fan. When the switch is in the first 3 positions, the relay is off, sending power to the fan via the resistor pack that controls the speed. When you switch to high, the relay connects the fan directly to the battery power post on the firewall.