need help with heater

[thao]

i have a 94 celica st. my heater works but only when i step on the gas pedal.
if it's parked, i have to rev my engine to get warm air. if i am at a stop light or stop sign,
the air becomes cold. i thought it was a fuse but it's not. any ideas?

[90celica]

could be a clogged heater core!

[Luckynumber5]

^ Thats a possibility, or a clogged cooling system, when was the last time you had it flushed? What kind of antifreeze/water mixture are you running, when was the last time you changed your thermostat?

[90celica]

could an improper coolant & water mixture cause this also???

[thao]

i had never changed my coolant yet. maybe i'll try that this weekend. where is the heater core located?

[markpc]

Your cooling system needs more than just water, the anti-freeze you should put in your cooling system also stops rust from forming inside the the engines internal parts. If the water is a horrible rusty brown drain the system and refill run the engine until it reaches full temp and check it again if it is not clean repeat but DO NOT PUT COLD WATER IN A HOT ENGINE as you can crack the block. If the problem is still there you will have to take out the heater matrix in the dash and either clean it yourself or buy another. Good luck and use anti-feeze. The matrix or heater core is in the middle of the dash and is a tiny radiator so be gentle.

[Luckynumber5]

Try the simpler things first, like I said above when was the last time your thermostat was changed? if its stuck open a little bit the engine will run a little too cool and you may not get any heat.