heater problem

I have an 02 GT with heater problems. If the car is idling, and the engine is warmed up, the fan blows cold, only when it's reved up to around 3000 rpm, does the heat kick in. Any ideas of what it might be?
Could it be a faulty thermostat, or maybe a vacuum hose. The car has 90,000 miles on it. Any help would be appreciated.

I have an 02 GT with heater problems. If the car is idling, and the engine is warmed up, the fan blows cold, only when it's reved up to around 3000 rpm, does the heat kick in. Any ideas of what it might be?
Could it be a faulty thermostat, or maybe a vacuum hose. The car has 90,000 miles on it. Any help would be appreciated.
Check your heater core first. It could most likely be clogged depending on how much you kept up with you radiator maintenece. If you want to check your thermostat take it out when your engine is cold put it in a pot of wateer and boil you should see it start to open when it gets hot enough depending on what temp stat you got. for the heater core just take the hoses off hook up a water hose turn it on and see if water flows through and out

my 86 gt does the same thing, except mine has to be in gear and moving for the air to turn warm. I've been told it was a vacuum leak but I haven't been able to find it yet. Good luck!

I cant remember how they are on the celica but on the firebird there located close to the pcm on the pas side of the engine compartment.

Im sorry i thought you was talking about the vacuum switch on the heater control that could also be the problem if you want to try to check that out. the new part cost a couple of bucks.