[FirebirdHank]

I was driving my '08 Grand Prix today , outside temp right around zero, and thought the air coming out of the vents should have been warmer. Both sides were set at 75 so I bumped my side up to 80. No difference so I bumped the passenger side up as well and still no difference. The air coming out is somewhat tempered but not really warm. Engine temp was up to normal, just below center of gauge. Bumped both sides up to 90, as high as it will go and still no diff.
The car will turn over 140k miles with-in the week.
Heater core partially blocked?
Heat control "doors"?
Thoughts please.

[Sirrotica]

Originally Posted by FirebirdHank

I was driving my '08 Grand Prix today , outside temp right around zero, and thought the air coming out of the vents should have been warmer. Both sides were set at 75 so I bumped my side up to 80. No difference so I bumped the passenger side up as well and still no difference. The air coming out is somewhat tempered but not really warm. Engine temp was up to normal, just below center of gauge. Bumped both sides up to 90, as high as it will go and still no diff.
The car will turn over 140k miles with-in the week.
Heater core partially blocked?
Heat control "doors"?
Thoughts please.

Check your coolant level, I had the same problem in my 99 GP and all it was was coolant loss, not enough to cause it to overheat, but enough to not have the heater core full. Adding about half a gallon was all it took to get heat again.

There is some engineering design in the HVAC on GPs that will make even the middle vents different temps. When the freon was low in the A/C I had 2 vents that were warm and one that was cold right next to each other in the center of the dash. Once I charged the A/C all three were equal temps. I suspect you'll have the same problem with not enough heat mixing with ambient air from outside.

It's a common problem with A/C, or heat from what I read on the net, because of how the system mixes exterior air.

[pontiac6269]

I would also back flush the heater core. Have done this to both of our 08 GPs. Made a big difference on my wifes car, was amazed by how much scale came out and it had 120,000 miles at the time. I have to do a coolant flush on mine so I will flush the heater core again.