Heater Blowing Cool Air While In Park!

Hello, my wife has a 2008 Chevy Impala with over 80,000 miles. When the weather is cold, the heater will blow cool air while in Park, even with the car warmed up. Then, once it is put in Drive, the heater begins to blow hot air again. Again, all of this time the engine temp gauge is in the middle position. Does anyone else have this problem?

Are you saying that if you put it in drive and sit still it will then blow warm air? Or are you saying that it blows cold while sitting still and warm while driving?

In any case, the first thing you need to do is check the anti-freeze/coolant level. If that looks good you likely need to burp the system of air and then find out why there’s air in it.

But please do clarify.

If the coolant level is good, both in the reservoir and in the radiator, the heater core may have an air bubble in it. The cooling system may need to be purged of air to restore proper heat to the car.