I have a 2007 maxima with 191k miles. I recently noticed when I put on the heat, it is cold at idle, but when I start driving its hot again. Anyone know what this can be? Why the hot air is cold when the car is stopped?

 

You have air in your coolant. You need to burp your coolant system. You can search on how this is done on YouTube. Very easy. This has been covered on this forum before as well. You can search above in the 6th gen section. Good luck, let us know if you have any questions.

 

This is a classic sign that the coolant in the radiator is starting to get low. When the engine is cold, remove the radiator cap and check the coolant level. The radiator should be totally full, not a bit of air.

If you can, do this when the nose of the car is slightly inclined. It helps to get air pockets out.