Heater problems?

[93 SE]

Last winter I got a brand new thermostat put in my car.My heater works fine as long as I let the car warm up for about 15 minutes.As long as my car is idling and the temperature gauge is showing like 130 or so degrees it heats fine,But when I get in my car and start driving within about 2 miles the temp. cools back down to about 100 degrees and stays there and blows cool air. I dont understand why it cools off after I start driving it.
PLEASE HELP ME!!! I'm freezing my ass off.

[Jchiasson]

Just a stab in the dark, but I think your thermostat is gone again. Sitting there idling the car should heat up quicker than 15 minutes. Also while idling there is no air flowing through rad unless fan comes on, so once you start driving the cooling effect is cooling the coolant but the coolant never actually comes up to temp, because thermostat is stuck open, before returning to the rad.

[93 SE]

Its been doing that since the last thermo got put in. Maybe it was a faulty thermostat or something.

[Jchiasson]

Or was put in backwards....

[jamiemc]

I had the same problem with mine and it ended up being a clogged heater core. All I did with mine was flush water through it backwards since it was still not leaking. I removed it from the car which surprisingly wasn't that hard to do or time consuming. I would fill it with water and force it through with my air compressor at low pressure. Once the water flowed through easily and was coming out clean I just put it back in the car and now it puts out heat again.