I just bought a 2003 Altima and found that the heater only blows hot air when the revs are up or the car is moving. The fan blows but the air temp changes drastically. Also the a/c cycles on when the heater is on. Is this normal for a Nissan? This is the first Nissan I've owned. This car does not have the automatic temp control.

 

Are your coolant temp. readings normal ? .... sounds like your thermostat might be stuck open. The a/c cycling on when the heat is on makes no sense....

 

I replaced the thermostat and it made no change. I took off the outlet hose to the heater core and only got a small amount of luke warm water coming out. I think the heater core is either stopped up or there is an air bubble in the line somewhere. I am going to take off the hoses coming into and going out of the heater core and blow through it with a compressor to see if that helps. I also heard that there is a tsb from Nissan with a very strict way of bleeding the system of air. I have not found it yet. does anyone know where I can get it?