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Toyota Highlander Heating Ventilation and Air Conditioning



  • kenlwkenlw Posts: 190
    Not to disagree but the heater bypass valve should already be closed (actually, in bypass mode) when the temp is on "cool" and the outlets are not on defrost.

    To cool a car down quickly after sitting in the sun, 1st put down ALL the windows, switch the AC to NON-recirculate and the highest fan speed. After about 1-3 minutes of driving, roll up the windows and switch the AC to RECIRCULATE.

    Why? The fastest way to move the cabin temp down from 140 is to get it to 100 by rolling down the windows. Then let the AC take it from 100, instead of trying to make it work against 140 air.
  • wwestwwest Posts: 10,706
    "heater bypass valve should already be closed..."'

    If you mean the reheat/remix vane/door then it will only be fully closed, and REMAIN fully closed, with the system in the max cooling position. On the other hand if you mean the actual coolant flow valve then the beancounters have been successful in eliminating that feature some years ago now.

    If the hot engine coolant is allowed to flow through the heater core then the radiant heating effects can be rather substantially adverse to the cooling capability of the system.
  • tonneytonney Posts: 1
    My 03 Highlander has a similar problem. When either the fan/vent or A/C is on, every once in a while the heat starts blasting. Very inconvenient. Had this diagnosed today - a resistor in the circuit board behind the panel will have to be replaced...$1,100!!!!

    Anything like this out there???
  • Yes, my 2002 V6 Highlander with manual ac/heat controls is also exhibiting this same condition. With the temp dial on blue (cold) and the fan on and the a/c on it periodically and intermitently blows warm air rather than cold air. It will do this for maybe 10 to 15 seconds and then go back to blowing cold air. So just $1,100. Are you going to get a second opinion?

    Also my V6 is using excessive oil and has blue exhaust when started in the morning. My dealer insists on measuring the oil usage requiring me to take it to them periodically to measure oil. Last trip used a quart of oil in 500 miles. I'm aware of the slug settlement but my dealer pulled the head cover off and told me there was no sign of slug. It's not sounding like they want to help me.

    Anyone have any suggestions, please help. thanks.
  • I had same problem a few weeks ago. It started about a month ago and it gets progressively worse. Toward the end. My AC was fine if ambient temp was below 80 but the hotter it got outside the hotter the air blew inside. Kind of defeats the purpose of AC. Dealer say it's a known issue but my extended coverage expited in May and it's dang hot here in TX... I paid the 1 K for the PWBA and it fixed it.
  • bdymentbdyment Posts: 549
    I am curious. What is PWBA?
  • jtumisjtumis Posts: 3
    How do we fix it? What is a pwba? Can I do this myself?

    Perhaps letting Toyota know may do something? &p_lva=&p_sp=&p_li=&p_accessibility=
  • mikefm58mikefm58 Posts: 2,882
    04 HL, 4 cyl, 40K miles, manual temp. controls, A/C blowing air that is barely cool, compressor not cycling on, freon pressure test is good. My wife is the primary driver and describes it kind of like some of the recent posts, works intermittently. I didn't see that anyone had anything conclusive. Any ideas?
  • kenlwkenlw Posts: 190
    if the compressor isn't cycling on, the air won't be cool at all. And if the compressor won't come on, how do you tell if the freon pressure is good?
  • mikefm58mikefm58 Posts: 2,882
    You're right about the compressor cycling, I must have not heard it correctly. I did notice the temp. control knob was quite loose as others have stated. I pulled the cover off and hand tightened the nut, seems much cooler now, but it's night time, still hot here in Florida but I'll know more tomorrow when it's hot.
  • I had the same problem with airconditiong on my 2005 Highlander. When I would select either heat or cold, it would be changing on its own every couple of secs. And then I found this forum and read some of your comments. I took off the temp knob, and there was a little screw which I just tightened and now it works like it should. Before I found these forums I was thinking of taking the car to the dealer who would probably rip me off. Thank you guys a lot.

    Since you helped me fix this problem, maybe you can this one also.

    Couple of weeks ago somebody broke into my car. They broke the drivers window. I ordered a brand new window from the Toyota dealer and raplaced it myself. The window works fine up and down, closes, opens but the only problem is the "Auto up". When I pull the which all the way up for the window to automaticly close, it come all the way up, and then by itself opens (comes down) half way and stays like that. In order for me to close it without opening on its own, I have to close the window manualy, not pulling the swich all the way up for the "auto close". I was told that I need to reset the motor and for that the dealer wants 150 bucks. I just don't think that it is worth that much money and that there is a another way to solve this problem. Does anybody know how I can reset this window so my Auto works?

    THank you in advance...
  • wwestwwest Posts: 10,706
    Try "normalizing" the window by holding the switch in the up position for about 20 seconds after the window is fully up.
  • Highlander 01 with the Auto Climate controls. Recently had the engine replaced and the AC works fine except when I put on the recirculation button. If the weather is cold and I turn on the recirculation button, it remains on... but when the weather is warm it seems to reach a certain point and then the recirculations starts to turn itself off and on, off and on. Any ideas
  • karen42karen42 Posts: 2
    my '04 Highlander A/C started blowing warm air. A check at my repair shop showed no freon so they added some and checked for leaks. Had cool A/C about 24 hrs, then hot air again. Freon added again but no leak ever found and again had cool air for about a day. The condenser and clutch are fine so I was told the evap core is probably the problem Also, when I just have the vent control on and the temp know turned too the cool side, hot air will come out when I go around a curve or corner. Very weird. Any ideas? I was told replacing evap core was very labor intensive therefore big $$. I live in an area where I need the A/C in the warm months. Thanks for any help/suggestions.
  • mikefm58mikefm58 Posts: 2,882
    I had a wierd similar problem like you described, but I wasn't low on freon. The air temp. in my case would also go between hot and cold by itself. Grab a hold of the temp. control knob and shake it. It should be firm. If it's loose, pull it straight out and check the nut that tightens down on the bolt. Tighten it down and use some lock tite so it won't come loose again.

    Good luck and let us know if this fixes it.
  • wwestwwest Posts: 10,706
    Many automatic systems will turn the system to fresh airflow within a few minutes if the A/C is not operating. Otherwise too much danger of moisture buildup in the cabin and the soon thereafter windshield fogging over.
  • howza1howza1 Posts: 1
    You Rock!

    Just fixed my Highlander in two minutes by tighening the nut.

    Car was blowing hot air even in the off position, and only hot with the AC on.

    Now it works like new.

    Thank You!!!!!
  • mikefm58mikefm58 Posts: 2,882
    Cool, glad I could help, I've even heard from others that had taken their vehicle to their dealer and been given huge estimates to replace major components of their A/C or heater systems. I've got to believe there is a TSB from Toyota somewhere.
  • Have now resolved the issue and it turns out to be TOO MUCH freon which causes the pressure sensor to cut out. I'm guessing that the garage I used filled the freon manually and put too much in. So if you have the situation where you can get cooling when the re-circulator is switched off, but when you put on the re-circulator the A/C continally switches on and off, then check the freon levels.
  • tidestertidester Posts: 10,110
    it turns out to be TOO MUCH freon

    I didn't know that was possible. Thanks for the info.

    tidester, host
    SUVs and Smart Shopper
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