SPONSORED LINKS

Heater will be warm until I turn on the fan, then it cools off

Tiny
ACREY
  • MEMBER
  • 2007 GMC YUKON
  • 5.3L
  • V8
  • 2WD
  • AUTOMATIC
  • 221,000 MILES
My heater will be warm until I turn on the fan, then the temperature starts to cool off. The rear heat works. I have checked the coolant level it is good. I have located the actuator beside the gas pedal, the one over the transmission hump and one on top behind the radio. How to know which one is the bad one?
SPONSORED LINKS
Monday, October 29th, 2018 AT 9:25 AM

9 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon.

Before assuming the blend door motor is no good, I would suggest checking the temperature of the heater hoses under the hood where they go through the firewall.

Touch them when they are hot and tell me if they are hot. It may be a clogged heater core.

As far as the blend door, do you have dual or single controls?

Roy

https://www.2carpros.com/articles/car-heater-not-working
Image (Click to make bigger)
Thumb
SPONSORED LINKS
Was this
answer
helpful?
Yes
No
Monday, October 29th, 2018 AT 12:24 PM
Tiny
ACREY
  • MEMBER
  • 5 POSTS
Both hoses are hot, and yes I have duel temp controls. One for drivers and one for passenger. It seems like the passenger side does not work as good as the drivers side does. Also, I hear a lite noise when I adjust the passenger temperature. Hear the same noise when I turn from inside to outside air.
Was this
answer
helpful?
Yes
No
Monday, October 29th, 2018 AT 12:32 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
I attached the location of the blend door actuator for the passenger side along with the procedure.

I still think you have a clogged heater core. You should remove both hoses and flush the core with your garden hose. Flush back and forth several times until you get an even flow from both sides.

Roy
Images (Click to make bigger)
Thumb
Thumb
Was this
answer
helpful?
Yes
No
Monday, October 29th, 2018 AT 12:37 PM
Tiny
ACREY
  • MEMBER
  • 5 POSTS
I will flush the heater core, but if it is that blend door actuator how in the world do you get it out of there? I took loose the glove compartment door and I can see it and feel it, but I do not know if I can remove it from this position.
Was this
answer
helpful?
Yes
No
Monday, October 29th, 2018 AT 12:46 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Did you read the procedure I sent you?

You remove the top cover and it is right there.

Roy
SPONSORED LINKS
Was this
answer
helpful?
Yes
No
Monday, October 29th, 2018 AT 12:49 PM
Tiny
ACREY
  • MEMBER
  • 5 POSTS
Not on a 2007 Yukon. Can remove the trim around the radio and temperature controls and remove radio and temperature controls and it is not accessible from there.
Was this
answer
helpful?
Yes
No
Monday, October 29th, 2018 AT 12:59 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
This is what it shows on my Alldata.

Roy
Image (Click to make bigger)
Thumb
Was this
answer
helpful?
Yes
No
Monday, October 29th, 2018 AT 1:06 PM
Tiny
ACREY
  • MEMBER
  • 5 POSTS
Thanks, I will try that.
Was this
answer
helpful?
Yes
No
Monday, October 29th, 2018 AT 1:18 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
You are welcome.

Keep us updated.

Roy
Was this
answer
helpful?
Yes
No
Monday, October 29th, 2018 AT 1:21 PM

Please login or register to post a reply.

Related Heater Content

Heater
GUIDE
Heater
Once the engine has been started and has run long enough to warm up the hot coolant is transferred into the heater core which is located inside the passenger compartment via...
VIEW MORE

Sponsored links