My AC/heat blower only blows on high

113,000 MILES • 5.2L • V8 • 2WD • AUTOMATIC
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MICHAEL CHURCH
  • MEMBER
  • 2 POSTS
My AC/heat blower only blows on high. I have replaced the resistor next to the blower and it was corroded and cracked. My fuses are good blower is good. Only thing left is the switch. Could this be the issue.
Sep 30, 2019 at 10:10 AM
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SCGRANTURISMO
  • ✓Experienced Mechanic
  • 4,897 POSTS
Hello,

There should be 3 resistors on the Blower Resistance Block. The reason your blower motor is only working on high speed is because when the slower speed switch is turned to low the electrical current must pass through all of the resistors to get to the blower motor. When it is on medium it only passes through half of them and when it is on high it doesn't pass through any of them. In this way the vehicle manufacturer controls the amount of electrical current going to the blower motor and how fast or slow it operates at. In the diagrams down below I have included a diagram of the heater circuit for your vehicle. Here is a link below for how to service a blower motor that you can use with the wiring diagram to inspect and fix the Blower Resistance Block in your vehicle:

https://www.2carpros.com/articles/blower-fan-motor-works-on-high-speed-only

Please go through these guides and get back to us with what you are able to find out.

Thanks,
Alex
2CarPros
Sep 30, 2019 at 1:58 PM
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MICHAEL CHURCH
  • MEMBER
  • 2 POSTS
So if I’m understanding; you I need to replace the blower motor also. Which no big it’s relatively easy to get to.
Sep 30, 2019 at 7:29 PM
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SCGRANTURISMO
  • ✓Experienced Mechanic
  • 4,897 POSTS
Hello again,

No. If you go all the way to the last section "Blower Fan Works On High Only" it will explain exactly what is going on with your vehicle, how to check the resistors, and how to replace them. Please go through this guide and get back to us with what you are able to find out.

Thanks,
Alex
2CarPros
Sep 30, 2019 at 8:17 PM
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