Lose heat when I turn to defrost position

Discussion in 'OT Driven' started by lutharthegreat, Oct 21, 2007.

  1. lutharthegreat

    lutharthegreat OT Supporter

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    I have a 1999 Toyota Corolla 4 cylinder 3 speed auto transmission with around 112,000 miles.
    This thing gets warm when you use dash or floor or combination. As soon as you turn it to defrost, it kicks the AC on ( I know this is normal in order to remove moisture from the cab) the thing will start blowing cold air out vents. Turn it back to dash or floor and it will take 3 min to become hot again. I replaced the thermostat and flushed the cooling system to ensure it is good. I ran the engine to get it to cycle the engine fan and it cycles fine and coolant apears to be circulating fine. I touched both inlet and outlet to heater core and they are hot to the point you cant hold them very long.
    Im not sure what to check next. Is there a ambient temp sensor that senses outside air in order to control the AC on heat? Anyone have any ideas? I have pulled the console the dash checked all the linkage and door operation I could find. I did not see any valves inline to be stoping the flow when defrost is used. The coolant lines to the heater core remain hot in this position as well.
    Any ideas?
     
    Last edited: Oct 25, 2007
  2. P07r0457

    P07r0457 New Member

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    it is doing exactly what it's designed to do. When on "defrost" you want cold air.
     
  3. E-dub

    E-dub New Member

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    Wrong. Cold air has nothing to do with fogged windows. If anything it would get worse as the cool air crystalizes the said fog.

    AC is a dehumidifier. It sounds like another problem, since any car should be able to run the heater AND AC at the same time, blowing warm dehumidified air.
     
  4. lutharthegreat

    lutharthegreat OT Supporter

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    I agree, I just can't figure out if it is a door inside the heater box not moving to the proper location or if the flow of coolant is minimal and can't compete with the AC. I wonder if it could be a relay that is not functioning properly?
     
  5. deusexaethera

    deusexaethera OT Supporter

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    You can't be serious.

    He wants DRY air, not COLD air. Most cars turn on the A/C when the climate control is turned to defrost mode, but it's generally assumed that the driver will crank up the heat as well. This dehumidifies the air.
     
  6. lutharthegreat

    lutharthegreat OT Supporter

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    :werd: Now what seems to be the major malfunction?
     
  7. bjonesy77

    bjonesy77 New Member

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    move to florida
     
  8. lutharthegreat

    lutharthegreat OT Supporter

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    That sounds good, the AC kicks some serious ass. But it is my sons car and he isnt looking to go south.
     
  9. alltracman78

    alltracman78 New Member

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    I know it's not your question, but are you sure you have a 3 spd auto?
    I'm pretty sure you have a 4 spd auto....

    Anyways, so your problem is you turn the blower to defrost and it blows cold air, then you turn it to dash or floor and it won't blow hot air for 3 min?
    Does it stay AC cold?
    Or just not get hot?
    Have you tried putting it on hot when it's in defrost mode?

    If the doors are working fine [put the fan on it's lowest setting and listen for it] there's the possibility the expansion valve is stuck [clogged?] slightly open, so when the AC is turned off it will continue to drip for a bit, giving you cold air.

    Or it just takes that long for the air to cool in the evaporator area, cooling the air before it hits the heater core....

    Since it apparently does get warm, it's hard to say exactly what it would be when I can't directly look at the car.
     
  10. lutharthegreat

    lutharthegreat OT Supporter

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    It is a 3 speed auto. I have the heat cranked to full hot and as soon as turn it to defrost it takes 30 seconds and it starts blowing cold air. I believe it takes the time to warm up the evaporator in order to blow hot air again. I would think even if the AC ran for a bit it should still be hot. This is very very strang and driving me nuts.
     
  11. deusexaethera

    deusexaethera OT Supporter

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    No way it's a 3-speed auto unless something's broken. That year the Corolla came with a 5-speed stick standard, or a 4-speed auto as optional equipment.

    They haven't made 3-speed autos since the 80's.
     
  12. P07r0457

    P07r0457 New Member

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    not true. The Dodge Neon had a 3-speed auto :mamoru:
     
  13. lutharthegreat

    lutharthegreat OT Supporter

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    Here is the proof, since you won't believe me, even when I drive the car from time to time.

    http://www.corolland.com/specs.html

    Scroll half way down to find your proof.

    Gear Ratios

    3-Speed Automatic (VE only)
    • 1st - 2.810
    • 2nd - 1.549
    • 3rd - 1.000
    • Reverse - 2.296
    • Differential Ratio - 3.421
    OK
    Now fix my damn problem.......
     
  14. deusexaethera

    deusexaethera OT Supporter

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    Wow. Why the hell did they even make a special 3-speed 'box?

    It sounds like a problem with the electronics. Turning on the defrost shouldn't stop coolant flow to the heater core.
     
  15. lutharthegreat

    lutharthegreat OT Supporter

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    Only thing I can think of is it is the blender inside the heater box. That is a shit load of work to tear apart. Looks like a weekend project unless I find something else.
     
  16. deusexaethera

    deusexaethera OT Supporter

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    I'd take it to a shop, personally. Shit like that, that takes hours and hours to do, isn't worth my time. An hour to change my headlights is one thing, but I'm all done with spending half a week's worth of evenings fixing something a shop can do in half a day. I got tired of that after I installed my gauge pods and my turbo timer. (The alarm bypass was a BITCH to get right.)
     
  17. alltracman78

    alltracman78 New Member

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    Yeah, I stand corrected :bow:
    You have an A131L.
    3sp auto.
    If it makes you feel any better, that's the third or fourth engine it's been mated to. It's been around since 89 or so, and is available all the way to 01.
    ick

    Anyways, do you know if you have cables or servos to move the doors?
    Have you tried listening yet?

    To pull the heater box you need to pull the evaporator.
    Which means you have to disconnect the AC lines.....
     
  18. lutharthegreat

    lutharthegreat OT Supporter

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    Yep
    This is the cheaper model, it is good other than heater.
    It has cables and all seem to be working properly. I was down to the box but ran out of time. I did notice that it's not as warm as it was, makes me wonder if the core may be plugged. I may tear it apart this weekend or just say screw it and call the dealer.
     
  19. alltracman78

    alltracman78 New Member

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    Ah, you don't need to listen if you have cables.

    They're all moving smoothly?
    No binding?
    Disconnect the cable from the arm and see how it feels with just the arm.

    Try changing from cold to hot that way.

    Have you tried going from AC to hot in any other mode to see what it does?

    Could be a blocked heater core, but if your heat works fine, I doubt it.

    Have you ever done your AC yourself?
    Taken any of the lines off?
    How long have you had the car?
     
  20. lutharthegreat

    lutharthegreat OT Supporter

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    They all work smooth and free.
    Going from AC to hot in any position takes some time to blow hot again.
    Im not convinced it's the core but I have seen stranger things happen.
    I was a diesel technition for 18 years, but I have always hated working on cars. There is just no room to work and it takes hours to get to what you want to fix. Hell, I could tear the heatercore/evaporator out of a semi in a couple hours. We got the car a few months ago, other than this, it has been a good car so far.
     
  21. alltracman78

    alltracman78 New Member

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    I was a diesel tech in the Marine Corps for 8 years [on tanks].
    I'm now a Toyota tech.
    I like cars better.
    Especially Corollas. They're easy, and not much on them.
    The evaporator should take an hour or less [most of that time is from discharging the AC] on a Corolla.
    The heater core longer, depending on if the whole dash needs to come out or not. I haven't done one on a Corolla, so I can't say.

    Try working on a Land Crusher or Sienna.
    They suck.

    Honestly, it sounds to me more like the AC is staying on [possibly a stuck expansion valve].

    Does it take a while when you go from cold [no AC] to hot?
     
  22. lutharthegreat

    lutharthegreat OT Supporter

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    The last 12 years I worked on CAT truck engines so I didn't have to work on the rest of the truck much. It will warm right up from cold to hot with the AC not being on. What is a good manual to get? Should I get an online or an actual book? I will check the flow through the heater core Saturday.
     
  23. alltracman78

    alltracman78 New Member

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    I wish I could work on just engines, they're what I really like.
    But, I'm not so lucky.

    The best manual by far is the factory one.
    It's MUCH MUCH better than Chiltons, Haynes, Alldata, ect.

    But it's expensive. They usually run over $100 for the set.
    I guess Chiltons is usually the best of the cheaper manuals.
    If you intend to look at wiring at all I highly suggest the factory wiring diagram at least.
    Everything is laid out and it color so it's very easy to read.
     
  24. deusexaethera

    deusexaethera OT Supporter

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    Hey alltracman, do you know how to score a factory manual for a 2007 Mazda MX-5? I know they exist, but I've only ever seen one and I didn't win the auction.
     
  25. alltracman78

    alltracman78 New Member

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    Have you tried the dealer?
     

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