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Heater not working

Tiny
DESERTRAT52
  • MEMBER
  • 1994 GMC SIERRA
  • 285,000 MILES
The arrow on the Temp. Control, Flash all the way across, won't adjust heat.
I have replaced the control unit and it does the same thing.
Is there some sort of relay to open the heater core? I'm stumped.
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Friday, November 15th, 2013 AT 11:45 AM

13 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
See if the actuator i pointed to in the pic is working that may be your problem. Here are tow guides to help you fix the problem.

https://www.2carpros.com/articles/car-heater-not-working

and

https://www.2carpros.com/articles/replace-blend-door-motor

Check out the diagrams (Below). Please let us know what you find. We are interested to see what it is.
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Friday, November 15th, 2013 AT 11:59 AM
Tiny
BOOPERIII
  • MEMBER
  • 1 POST
I had to get a new actuator cost me $67.00 all fixed!
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Tuesday, April 16th, 2019 AT 2:09 PM
Tiny
TRUCK000
  • MEMBER
  • 10 POSTS
  • 1994 GMC SIERRA
  • 200 MILES
A/c doesnt get cold heat doesnt get hot. Air sounds like it shud b blowin hard but its barely comin out. Cant even feel it on low setting. Can still hear it tho. Changed thermostat and flushed core?Please help
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Saturday, December 26th, 2020 AT 2:47 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Actually, it sounds like there is a problem with the blend air door. This door is near the heater core. Its job is to turn one direction to allow the fan to blow air through the heater core and heat the vehicle, and the other direction is for the AC to cool the vehicle. Based on your description, it sounds like it is stuck in the middle. Therefore, you don't get good AC or heat and there is less air entering the vehicle.
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Saturday, December 26th, 2020 AT 2:47 PM (Merged)
Tiny
TRUCK000
  • MEMBER
  • 10 POSTS
How do I get to this door and I have read something about a blend door actuator is that the same thing? It is a digital control if that matters.
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Saturday, December 26th, 2020 AT 2:47 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
It will be next to the heater core. The actuator is the device that moves the door. Yes, it can be bad.
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Saturday, December 26th, 2020 AT 2:47 PM (Merged)
Tiny
TRUCK000
  • MEMBER
  • 10 POSTS
What about the blend door motor? And is there a way to tell which one it is. When pushing buttons on the control panel I can hear clicks coming from something near the heater core
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Saturday, December 26th, 2020 AT 2:47 PM (Merged)
Tiny
TRUCK000
  • MEMBER
  • 10 POSTS
Also will I have to open up the core housing to get to the door
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Saturday, December 26th, 2020 AT 2:47 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Everything may be working but need adjustment. You need to try it while you check the part. If you hear it, chances are something is disconnected or out of adjustment.
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Saturday, December 26th, 2020 AT 2:47 PM (Merged)
Tiny
TRUCK000
  • MEMBER
  • 10 POSTS
Will I have to open the core housing to get to the door
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Saturday, December 26th, 2020 AT 2:47 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Yes
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Saturday, December 26th, 2020 AT 2:47 PM (Merged)
Tiny
TRUCK000
  • MEMBER
  • 10 POSTS
Ok s its not the blend door. Found its working smoothly. Although there was a gadget unplugged. Plugged it back in (into a box that looked like the actuator box in the fron but this was in back (motor side) ) after plugging that in the box mad a loud clicking noise until we unplegged it. Any ideas
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Saturday, December 26th, 2020 AT 2:47 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
I would need to see a picture. It sounds like an actuator.
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Saturday, December 26th, 2020 AT 2:47 PM (Merged)

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