heat only works when driving

Posted by 93laser1g, Oct 31, 2011
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  1. 93laser1g

    93laser1g Proven Member

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    green bay, Wisconsin
    any idea why my heat only works when im
    driving at high speeds?
    #1
  2. 91stocker

    91stocker Proven Member

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    Vassar, Michigan
    Low coolant?

    Edit: Do you mean the blower motor/fan speed or the heat itself getting hot?
    #2
  3. 2point3Tsi

    2point3Tsi Proven Member

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    Maple Valley, Washington
    Thermostat stuck open
    #3
  4. BradM

    BradM Proven Member

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    Annapolis, Maryland
    +1 for low coolant. Had an Mr2 that leaked coolant, it happened all the time.
    #4
  5. CanadianTalonTC

    CanadianTalonTC Proven Member

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    Lethbridge, AB_Canada
    Your thermostat may be stuck open and it only heats up with a higher load on the engine. What does the gauge on the dash say when your driving around the city?

    Check coolant level also like the guy above said.

    Joel
    #5
  6. Abe'sGST

    Abe'sGST Proven Member

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    Goldsboro, North_Carolina
    i had that problem b/c this weekend i flushed my coolant. What i did wrong was that when i filled it with new coolant i closed the drain plug before i started filling it up. To make long story short, i had to "burp" my cooling system b/c i had air in it
    #6
  7. 93laser1g

    93laser1g Proven Member

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    green bay, Wisconsin
    my heat gauge is always right in the middle but drops down a little when the fan turns on.
    #7
  8. CanadianTalonTC

    CanadianTalonTC Proven Member

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    Lethbridge, AB_Canada
    Weird, when I did mine I had my drain plug closed and it filled fine. How did you "burp" it?

    Joel
    #8
  9. ktgurl87

    ktgurl87 Proven Member

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    Elizabeth City, North_Carolina
    OP... what exactly is the problem? You say your heat only works while you're driving, then you say that your temp gauge drops when the fans kick on? That's normal.

    So are you talking about your temperature gauge... or the actual heater in the cabin of your car?
    #9
  10. Abe'sGST

    Abe'sGST Proven Member

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    Goldsboro, North_Carolina
    it works like bleeding your brake lines, if you bleed the lines, tighten them up and then pour brake fluid in the master cylinder you will have air in the lines afterwards...i removed my radiator cap, started her up, run it at about 1500 rpms to let it get to running temperature and when the thermostat opens and coolant starts to cerculate the trapped air gets out, then i just top it off with more coolant

    what he's saying is that his heater doesn't work unless he's driving at cruising speeds
    #10
  11. natural laser

    natural laser Proven Member

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    Spokane, Washington
    My 91 laser seems to do the same thing, not moving its just pushing air, when im actually driving is when it heats up and actually blows warm air. and i checked my thermostat so in my case thats not the issue
    #11
  12. mb3000

    mb3000 Proven Member

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    Myrtle Beach, South_Carolina
    Might have some blockage in your coolant system.
    #12
  13. Abe'sGST

    Abe'sGST Proven Member

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    Goldsboro, North_Carolina

    if it's not the thermostat, it can either be some blocking in the colling system or air in it
    #13
  14. ramsack

    ramsack Banned Member

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    West Lawn, Pennsylvania
    The heater core circuit is the primary loop. It will get a constant flow of coolant even if the thermostat is wide open, or non-existent. The temperature of the coolant entering the heater core is not controller, whatsoever. You probably have a blockage in the heater core, itself. Just get a new one and put aside a day to replace it.
    #14
  15. TSiAWDRatlemstr

    TSiAWDRatlemstr Proven Member

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    Boise, Idaho
    I have had this happen a couple times. Actually, it happened just two hours ago coming to work :) The first time that it happened, I had a small pinhole leak in one of the lines and the coolant leaked out once it was up to temp and the lines were pressurized. I checked the system with a coolant system pressure tester and found the leak. I replaced the line, refilled the coolant, bled the system of air (running with the cap off, filling up the overflow tank) and made sure that the thermostat opened. It happened again this morning, and it was a gusher! I know what I'm doing tonight :) The reason that the temp fluctuates, as far as I can figure out, is that there is still coolant being pushed through the system as the rpm increases to flow to the heater core, just not enough to flow at idle or low rpms. Happy leak fixing :)
    #15
  16. 93laser1g

    93laser1g Proven Member

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    green bay, Wisconsin
    okay i am talking about the heat inside the car. when idling i turn the blower on and nothing comes out of the vents, no cold air no warm air, nothing. when i start driving the heat begins to blow out of the vents. and the faster i drive the harder it blows. i need these solved asap as i live in wi and winter will be here soon and so will my baby so i need heat
    #16
  17. mchustle

    mchustle Proven Member

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    johnson city, Tennessee
    Sounds like it may be your blower motor or simply a fuse.
    #17
  18. UrbanSmoker

    UrbanSmoker Proven Member

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    Oakville, ON_Canada
    +1 ^ op, you didnt say anything about the FANS not blowing ANY air.... again +1 to mchustle
    #18
  19. Dsm78

    Dsm78 Proven Member

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    Fort Wayne, Indiana
    Try flushing out your heater core. If it is plugged up you will experience the problems that you are referring to.
    #19
  20. XLR8

    XLR8 Proven Member

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    Kingston, New_Hampshire
    Fuse might be having bad contact. I had a issue once on a car, I did every diagnostic I could and still not working. Turns out the fuse box had some corrosion in it, ended up having to tweak the sides of the fuse in opposite directions to get good contact. Ever taken apart a fuse box, layer by layer? It is amazing how everything is connected inside.
    #20
  21. blindboarder_02

    blindboarder_02 Proven Member

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    Kenosha, Wisconsin
    I would say a bubble of air in the lines. I would try Abes post. He explains it perfectly. After you put the cap back on, fill the overflow so it can pull some if it needs any.
    #21
  22. casperfast

    casperfast Supporting Member

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    Salem, Oregon
    the only reason you feel air when driving is due to the air blowing in cowl while you are moving. the blower motor is out or the fan switch in your dash. might be a fuse, but fuses dont blow for no reason. has nothing to do with the cooling system, coolant, radiator or the heater core.
    #22
  23. knochgoon24

    knochgoon24 DSM Wiseman

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    Rochester Hills, Michigan
    I had this happen when the coolant was really low. The coolant wouldn't circulate well until the rpm increased.


    EDIT: Just re-read the problem. Oops.

    Try checking the fuse. You can also test the blower fan by applying 12v to it. If it turns on, then you have a problem somewhere else in the the electronics.
    #23
  24. 93laser1g

    93laser1g Proven Member

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    green bay, Wisconsin
    okay does anybody know where the fuse is located?
    is it under the hood or under the dash b y the pedals?
    #24
  25. Anubis_4_99

    Anubis_4_99 Proven Member

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    omaha, Nebraska
    I dont personally know, but why not just check both areas? Search for any blown fuses and address them.

    It is also possible that your blower motor has seized, or just plain stopped working. Try replacing the fuse, but if it is popped, and pops again, check your blower motor and make sure it spins freely.
    #25

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