Why does my heater blow heat when I am running over 2k rpms?

SOURCE: heater doesnt heat

could be thremostat, heater core, or you may just need anti-freeze/ water

SOURCE: heater blows cold air

the heator core has gone out this is a divise that uses hot coolent from the engine to heat the air that blowes tru your vents it is located behind the glove box some times it's tricky to reach look under the hood to find 2 hoses running side by side in to the fire wall on the passenger side to pin point the location

SOURCE: 2003 Mitsubishi Eclipse GS blows cold air in heat mode.

ok here we go and you aren't going to believe it...
I replaced the thermostat step one

I noticed that I had a small leak at the engine side of upper hose fixed that by taking it off and cleaning it and putting the hose back on Step two

then while refilling the reservoir with coolant i found that the hose that was supposed to be in the fluid was curled up on top and not sticking down in the fluid where it should be.
played with the hose until i got it to fall down in the reservoir where it should be Step 3

I started the car with the radiator cap off and let it run until it got to normal operating temp. and keep filling the radiator with fluid until the level stayed constant. Then put the cap back on and test drove. Everything worked fine haven't had that much heat in awhile and it kept blowing hot even when i stopped and let it idle for ten min.during test drive. Checked reservoir when I got home and had to add a small amount of coolant but not much.

I really think that the hose in the reservoir not being in the right place and pulling air into the system instead of coolant is the real culprit of this drama, but i replaced the thermostat to be safe.

SOURCE: heater blows cold air

I had the same problem with the heater only working when accellerating. Found the overflow tank pick up tube was kinked. This of course made my coolant level low. So when the cars hot the coolant would push into the overflow, but when the car cooled the kink would prevent it from flowing back to the radiator.

Marvin

• 85242 Answers
• Posted on Oct 25, 2012

SOURCE: No heat blows cold air

In all modern cars there is a tiny DC electric motor driven gear drive that moves a plastic door that blends heated and cooled air from the AC and the heater core, this is called (interestedly enough) the air temperature control blend door actuator. The motor that moves this door fails because the door starts sticking from warping, most common complaint is no heat but it can be no AC as well. To replace these parts (blend door and blend door actuator) you must remove the entire dash from the car.