Question about 2003 Mitsubishi Eclipse Coupe

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2003 Mitsubishi Eclipse GS blows cold air in heat mode.

The heater does blow hot air while in motion but blows cold after stopping at a light or sign. Please advise, Thank you, Mike

Posted by mkgradle on

  • 11 more comments 
  • Anonymous Nov 24, 2008

    I have exactly the same problem w/5 spd trans. Whe at idle cold air blows in.

  • Anonymous Nov 26, 2008

    I have exactly the same problem in my 03 RS. I've found by revving the engine, it will blow hot air again. At idle, it won't. I'm attempting to find the answer tonight.

  • tellington22 Dec 07, 2008

    The same thing is happening in my '00 Eclipse GT. Cold air during idle and Warm air during acceleration.

  • kimmie2879 Dec 09, 2008

    Same Problem! Mine is an 03 GT and I live in Buffalo!!! We changed a fuse in the fuse box but it keeps blowing as soon as we turn the heat on.

  • Frankie1976 Dec 10, 2008

    I have the exact same problem as well. I drive a 2003 GTS. I'm not very happy in the cold mornings

  • faaesh Jan 23, 2009

    Same car, same year, same cold when idling/coasting, hot when engine accelerating. Why are these all failing at the same time? Is this a manufactuing defect?

  • protoman350 Jan 27, 2009

    I have the same problem. I thought it might be the thermostat so i replaced it to find my old thermostat visibly fine. I still replaced it but the problem is not resovled.

  • Anonymous Feb 21, 2009

    Same problem No heat at Idle / heat blows when reving also temp gage goes crazy ...03 Eclipse gts

  • Anonymous Feb 28, 2009

    Yeah I have the same problem! 03 gt did anyone find a for sure fix?

  • Anonymous Mar 02, 2009

    all of you guy are ***

  • rob meloccar Nov 22, 2013

    it always blows cold or hot don't matter if revving or not

  • Anonymous Mar 17, 2014


  • Anonymous Mar 24, 2014

    fan blows, but want blow heat when it is turned on. What is causing this?



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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.

Posted on Feb 21, 2009



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So I am the original owner of 2000 Eclipse and have taken it back to the dealer for the 1st 5 years and they would replace a hose and tell me that there was a leak and the coolant was low. Oddly enough I never witnessed leak or saw any a/f on the drive. Plus the overflow is still at full. I fed up with the dealer(warranty ran out) so I must do this on my own or suffer the arctic Cleveland commutes to work. My driveway slopes down and typically the car is parked nose down the drive. By luck I parked it bassackward or Nose Up. and had heat when the card idled in the drive. The Heater hoses are at the highest part of the cooling system and any deficiency in the coolant level replaces hot water with cold air in the heater core. I still can't tell you where my coolant goes each and every year nor do I understand why it won't **** it out of my overflow bottle when low. I just top off radiator frequently and alls well.

Posted on Oct 06, 2009

  • Anonymous Feb 08, 2010

    Alright THIS IS
    COLD years.

    Problem Description:
    Cold air at idle Warm air on

    Overfill tank is full and losing

    Radiator is low and needs to be topped off

    Why Do I have to fill my radiator
    when my overflow tank is full to the brim?

    Years ago, I also found the hose that is in the
    overflow tank had fallen off in the tank and had put it back on and secured it
    with a hose clamp since mitsu was to cheap to do

    I thought this was the answer that I had been searching for. Unfortunately I still had to cup myself at stop lights
    to stay warm.

    Hint: Don't trust a hose clamp to seal off the hose with out
    pressure testing as I found that the clamp I put in the overfill tank was
    leaking also

    DO THIS:

    1 take the hose off of the radiator
    which goes to the overfill tank
    2 Remove the Overfill tank cap and entire
    hose system.
    3 Fill kitchen sink with water.
    4 force air through the hoses
    while plugging the other end.
    5 clamp off any leaks until their are no air
    bubbles in the sink
    6 Replace the hoses and top off radiator and coolant tank
    if necessary.
    7 make sure to clamp the radiator cap hose as well this is the
    one that got me.
    8 run engine and enjoy the heat

    RARTHER69 hit the nail on the head and now it's too dang




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 same here. we flushed the radiator, and installed a new thermostat. the other was clogged so bad it would not open up. It blew "warm" for a day now its back to blowing cold thing to do is check a heater fuse...if thats not it. then the heater core...if thats not car.

Posted on Jan 05, 2009

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Heater blows cold air

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