Why would your heater only blow cool air and how do you fix it on a 2002 Nissan Altima?

Answer 1

AnswerIf engine temp is normal I would check for a stuck blend door or blend door acturator. Are more simple just a broken control knob.

I worked at a Nissan dealer for 18 months and we'd get a lot of these in. The cold heat at idle is accompanied by a sloshing noise from behind the dash - you've got an air pocket in the heater core. What we used to do was lift the front end of the car about 3 feet off the ground using the hoist and take the rad cap off. Then we'd run the engine at a fast idle (jam a screwdiver against the throttle stop to hold it fast or put a slight weight on the pedal if it's Electronic Throttle Body. Run the heater on full heat and the engine like this. You'll see the rad 'burping' as the air in the cooling system travelling to the highest point it can - the open rad cap. Top up with a 50/50 mix of coolant and water as you go. When it burps no more, you have a full cooling system and should not suffer any more "cold heat".

If you do this yourself, PLEASE use jack stands, block the back wheels and put the parking brake on!!!