Heater/AC fan only works on high

Tiny
CHUCK99999
  • MEMBER
  • GMC SIERRA
My truck is a 1997 GMC Sierra with a 5.7l Vortec engine and 80,000 miles. The fan only works on high. The blower motor itself is only 2 months old so that shouldn't be the problem. Is it the switch or is there some sort of regulator between the switch and fan that has blown?
Saturday, November 3rd, 2007 AT 11:00 AM

2 Replies

Tiny
CHEVY22
  • MECHANIC
  • 1,375 POSTS
Most likely if you have one speed only you will need to replace the blower motor resistor, it is located under the right side of the dash. Sometimes hard to see because the bottom is black but it does have a connector and two 7mm bolts in it and not too expensive.

Jim
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Saturday, November 3rd, 2007 AT 5:50 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good evening,

The power for the blower resistor comes from the control head. You will need to verify the power on the brown wire to the control head.

https://www.2carpros.com/articles/how-to-check-wiring

The blower resistor is the most common failure but the voltage needs to be checked to the resistor to be sure.

Roy
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Thursday, March 26th, 2020 AT 4:43 PM

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