heater blows cold air when at idle even when temp is at normal?


Asked by Douglasfir Mar 09, 2013 at 11:50 PM about the Chevrolet Impala

Question type: Maintenance & Repair

when the car is accelerating it blows warm air but as soon as u come to a stop and idle say st a light
it blows cold air ,even if u free rev it ,it stays cold ...Any help please!

15 Answers

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The device known as the thermostat is supposed to let the engine warm up, then as soon as the coolant reaches 195 will open up and let the warm coolant circulate thru your heat exchanger...if it never gets up to 195 because it is stuck open, you will have minimal heat, just as you describe....in summation, change the thermostat and all will be skippy in skippy town.

9 out of 9 people think this is helpful.
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...also 195 is operating temperature...if it never gets there you'll have incomplete combustion, resulting in smokey exhaust and poor acceleration...if you didn't notice.

2 out of 2 people think this is helpful.
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be sure to have your mechanic 'belch' the heat exchanger or it will become air-bound after the thermostat replacement.

5 out of 5 people think this is helpful.

The dampers for the duct work of heating systems are controlled by vacuum. If at idle and car is at operating temp with heater on and you feel air coming out the vents but its cold and without touching any controls you start to drive and warm air starts coming out of them I would check for a vacuum leak going to the controller. As you drive faster the vacuum increases and will provide enough pressure to move the damper but at idle with the vacuum leak not enough pressure there to move it. This vacuum line will be coming from the intake thru the firewall to behind your heater controls. This is what I would check after you check all of what bob stated. Have to have heat in the heater core first.

15 out of 15 people think this is helpful.

Sounds like a coolant flow problem. Newer Impalas have electronic motors that control the doors under the dash for air temperature. Could be a partially clogged heater core. HTH. -Jim

2 out of 2 people think this is helpful.

Same with my 05 Impala. I changed the thermostat after it started blowing cold air. No improvement. I bled the brass bleeder on top of engine, filled resevoir, etc. It gets warmer the more gas you give it, then when letting off gas goes cold again. Both hoses to and from heater core get hot, so I am at a loss...

25 out of 25 people think this is helpful.

Sounds like the air temperature door under the dash isn't working correctly. HTH. -Jim

3 out of 3 people think this is helpful.

I am having the same exact problem in my 05 Grand Prix... going to change the thermostat tomorrow.

Roberta Fisher

My car is always doing the same thing. Blows hot air until I stop. is this a Chevy thing or what? I have a 2007 Saturn aura, same as a Chevy Malibu .

1 out of 1 people think this is helpful.

I wish I new what was going on. I changed my thermostat, radiator, radiator cap, anti freeze, and I still have the problem. At idle, its cold air. driving down the road, warm air. I have a 1995 Mitsubishi Montero SR that I purchased new. A great machine, but this is puzzling.

2 out of 2 people think this is helpful.
Jesus Molina

I've been having the same issue with my 2007 impala. Done many coolant flushes and replaced thermostat. Recently had it flushed again, heater was working for about a month now it's blowing hot air only when I'm hitting the gas. Been having this issue for two winters now. My mechanic has no idea what's going on. thinking about replacing heater core? Any suggestions?

15 out of 15 people think this is helpful.
Casey Alexander

I fixed this issue for good in my grand prix. What it is is the coolant isnt being filled properly. Try running the vehicle for 5-10 minutes with your radiator cap off, and after it has been circulating for a little bit, fill it with coolant from the open cap and allow it to fill up your coolant container. This will flush out your bubble and solve you problem. At least it di for me...

2 out of 2 people think this is helpful.
Roberta Fisher

I took mine in. It was a blown head gasket. Thank god it was still under warenty. It would have been close to 2 grand


I have tried several things on my 07 Impala. Total tune up including new thermostat. Nothing. Just had the heater core replaced, still no hot air when idling. Not over heating so no water flow problem. I will try the radiator, cap off while idling, adding coolant directly to opening and see what happens.

Joey Charity Gish

I changed my thermostat n my 2009 impala and done a flush and then my car started to do right on heat

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