sorry guys, i know this is OT with maxima's, then again, i could just lie and say its happening to my car but my father's MPV is getting no heat and the dealer diagnosed the wrong thing and now i THINK he's about to lose 600 dollars because the problem wasnt correctly stated by dealer. In general, what causes loss of heat? When car is warm and your climate control is manually put on hot, what makes it throw cold air? How do u fix this? thanks guys.

It could be your temperature sensor

Dude... sounds like your dads heater core is clogged in his MPV. I have seen it happen many times. Or... the heater valve may be malfunctioning. What diagnosis did you get from the dealer?

the flap that directs air, either from the heater core or AC unit (damn, cant remember the name, not the condenser, the other one...) could have gotten stuck too, thats not uncommon. does his AC work?

Does he get ANY heat? like when the RPM's are up?

It could also be something as simple as being down a couple of quarts of coolant - not enough coolant avialable to pump to the heater core.

Ok, this might be EXTREMELY IMPORTANT: If it is not what everyone else has suggested, check the water pump. DO NOT DRIVE THE CAR if you suspect that it could be the water pump. The damage could be painful and unreversible.

the heat has not been working for a FEW months now. and yes the air conditioner works. I'm gonna to talk to him to see if its any of these problems and see what he says, thanks guys

Did you by any chance change the coolant recently?
I had this problem with my other car (GS300), not my max. after I changed the coolant the air from the heater was cold eventhough the eng was warm.
I just parked the car uphill, and reved the eng. with the heat at max. to get the traped air pocket out of the heater core.
No problem since......

Good luck,
Michael7278

i'll be very ****ed if your idea works

hello?? stuck open thermostat anyone.change that and the gasket and add new cooalnt.problem solved

Yea, most likely the thermostat or heater core. However, if you had your coolant flushed, you might have a bubble of air in your radiator, which is really bad.

THERMOSTAT