Why does AC change from AC to heat in summer and.

Tiny
CAMPERMONROE
  • MEMBER
  • 2004 GMC YUKON
  • 160,000 MILES
Why does ac change from ac to heat in summer and heat to ac winter front could be drivers side passenger side or both never effects rear
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Wednesday, April 3rd, 2013 AT 2:32 AM

15 Replies

Tiny
BLAZE45
  • EXPERT
It sounds like your blend door could be jammed open or closed. Another common problem is there is a valve that allows hot water to come through the heater core at the firewall. This could be wedged open/closed. Check to make sure it operates properly. You should be able to hear the blend door moving back and forth when you turn the climate control knob to hot/cold.
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Wednesday, April 3rd, 2013 AT 2:53 AM
Tiny
CAMPERMONROE
  • MEMBER
It doesn't do it all the time just intermittent the only way to reset it is stop vehicle turn off restart it will be ok for for 10 minutes or all day just depends on how lucky I am
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Wednesday, April 3rd, 2013 AT 2:59 AM
Tiny
BLAZE45
  • EXPERT
Try a system reset. Start engine, turn off climate system. Stop engine. Turn key on, but do not start. Leave for 10 seconds. Turn off and pull key out of ignition. Leave out for 30 seconds. Restart engine, turn on air conditioning. Try that and see what you come up with.
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Wednesday, April 3rd, 2013 AT 6:44 AM
Tiny
CAMPERMONROE
  • MEMBER
I tried something similar to this last year it did not help
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Wednesday, April 3rd, 2013 AT 11:59 AM
Tiny
BLAZE45
  • EXPERT
89018964 Module, HTR & BLO & A/C CONT this is an updated part # for the blower control unit if that has gone out.

Check this unit as the terminals can melt on them sometimes.
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Wednesday, April 3rd, 2013 AT 3:20 PM
Tiny
CAMPERMONROE
  • MEMBER
There is nothing wrong with the blower motor
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Wednesday, April 3rd, 2013 AT 6:27 PM
Tiny
BLAZE45
  • EXPERT
Let me know how the system reset goes.
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Wednesday, April 3rd, 2013 AT 7:57 PM
Tiny
BLAZE45
  • EXPERT
If the problem occurs intermittently I would venture to say there is a loose connection/short that is happening in the system.
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Wednesday, April 3rd, 2013 AT 8:00 PM
Tiny
RIVERMIKERAT
  • MEMBER
The control unit that Blaze mentioned could also be the culprit since it helps determine whether the system blows hot or cold.
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Thursday, April 4th, 2013 AT 2:53 AM
Tiny
CAMPERMONROE
  • MEMBER
I have reset system will let you know if it works with in a few days
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Thursday, April 4th, 2013 AT 4:21 PM
Tiny
RIVERMIKERAT
  • MEMBER
Ok. We'll be waiting.
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Friday, April 5th, 2013 AT 3:25 AM
Tiny
CAMPERMONROE
  • MEMBER
Ok relearn did not work passenger side now blowing hot with ac on
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Friday, April 5th, 2013 AT 11:58 PM
Tiny
RIVERMIKERAT
  • MEMBER
Can you cycle the unit through the various settings and listen for the doors to actuate? Do they seem to be moving?
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Saturday, April 6th, 2013 AT 1:44 PM
Tiny
CAMPERMONROE
  • MEMBER
Yes today it is working fine right know I might change both actuaries this week many they are both weak before changing the control module don't know what else to do. Need to fix before wife kicks me out of bed
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Saturday, April 6th, 2013 AT 2:42 PM
Tiny
RIVERMIKERAT
  • MEMBER
Ok, let us know how it goes with the actuators. Without being able to see and touch it, those would be my guess as to the culprit.
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Saturday, April 6th, 2013 AT 5:11 PM

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