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2006 GMC Envoy - Only works on high

blower motor quit working…now it only works on high after replacing blower resistor

Check HVAC fuse 44, 30 amp.

Tester

Or a blower resistor, probably behind the glove box, cheap part easy fix.

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Take a close look at that resistor connector , sometimes they will partially melt and need to be replaced .

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I like the advice that @Tester gave about the fuse. There are separate power sources feeding the speed control and the full output circuits. No power is getting to the resistors.

If no power was getting to the resistors no power would not allow it to run on high. See previous response for my suggested repair.

Well the poster already replaced the resistor pack and then the blower only worked on HIGH. Looking at the schematic it seems to show that when the blower relay isn’t activated, it is tied to direct power from a different source than the normal supply to the blower is tied to.

Could be the blower motor switch is kaput too. OP could – as a test — disconnect the top input to the switch then try jumping around the switch to the various speed taps on the other side, see if the motor worked then. Common sense says to check the fuse first.

Looks like the blower motor relay might be stuck closed, try swapping it out with another identical relay from the AC or whatever.

Voltage from fuse 44 holds the relay in high or the relay is stuck.
No voltage from fuse 44 and the relay connects to the blower resistor.And then to fuse 44

After looking at the schematic AGAIN and thinking about the design, I now think @87_Ranger makes a good point about the relay. The blower relay doesn’t turn on until the speed control is moved to the HIGH position. That closes the relay contact and ties to the power source that bypasses the speed resistors, which does work. So for that to work fuse 44 has to be working to supply power to the switched HIGH speed position. That now leaves the relay contact for the speed settings in question.

Yeah,Cougar it’s a shame the OP didn’t take a quick look at a GOOD wiring diagram like the one Tester posted before replacing that blower resistor,
Might have saved himself 50 or 60 bucks

I have the factory diagrams for the cars i own and they are so much better than anything in a Chiltons or Haynes

I concur with you @87_Ranger . There is no substitute for a factory service manual and is why I have them also. Good call on the relay.