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Toyota Highlander Heating Ventilation and Air Conditioning



  • wwestwwest Posts: 10,706
    Too much refrigerant and the pressure switch that activates the compressor is always open, especially if the OAT is HIGH.
  • jannersjanners Posts: 1
    It is definitely the nut behind the control knob. i believe htis is a fault with Highlanders. It comes loose and finally the wires break behind the knob making the heat either full on or intermitent.
    I tried to solder the wires but in the end bought a replacement unit on ebay for $200. the dealer wanted $700 to do it and $565 just for the part. it is easy just pry out the facia and then undo 4 screws the whole thing pops out and then replace with new or used unit.
    If you are good at soldering it could save you a lot of money. If it has only just happened you may be lucky and get away with tightening the nut behind the control knob

    Good luck!
  • karen42karen42 Posts: 2
    I took the temp control knob off and the nut was loose just like you all said,so I tightened it. It helped with the cool/warm air blowing when I just used the vent,. but my A/C still blows warm air when I turn it on. I'm afraid I'm going to have to find a repair shop to check it out. I will not go to the dealer since I don't really trust them not to rip me off. Thanks for all the suggestions.
  • ojnucciojnucci Posts: 3

    Could you tell me which part it was you bought on ebay? I would like to do the same thing- my Highlander has been doing this for about 2 years so I've been just half-turning the temp control knob to get cold (though it has still been very intermittent!). Its been a huge thorn and I've been quoted from two separate shops at over a grand to replace the "Blender Box."

  • ggartnerggartner Posts: 3
    Janners: the "Blender Box" is probably what I bought. It has been a while, but I took the module that the knobs hooked into to a junk yard. They found the replacement part - the first one they found, did not work when I installed. They searched other locations around the state and found another one. The second one worked like a champ. I think I paid about $125 for the part finally.
    Sorry this is not more help.
  • ojnucciojnucci Posts: 3
    This helps a lot actually. I have just started the online junk yard scavenging today. However, after tightening the bolt behind the temp control knob it works much better--so I may give it a few months!
    Thanks Gary.
  • kburger1kburger1 Posts: 2
    thanks for pointing me to the loose nut behind the temperature control knob. as thanks here is further info. If you tighten the nut and it still doesnt work try taking the nut off completely and gently move the knob to different positions with the blower on max air. If it changes from hot to cold in different positions the 3 wires connecting that control switch to the next upstream board are severed (broken solder joints) you can remove the whole assembly with the radio first disconnect the positive terminal of the battery. the trim around the radio and ac controls just pulls straight out from the bottom and then at the top very easy. disconnect the wires they are keyed, large connectors goto the air controls, small connectors to the radio. you need to resolder the wires back onto the control knob board. I have been soldering along time and it was hard. good idea to test joints with a multimeter. if you short any of them it probably wont work. you will show continuity between wires even when its done correctly, 2 have full continuity and you also have 1 with a resistance of like .7 which i think is an inline resistor. i replaced the existing grey flate wire with 3 small guage individual wires. label it so you dont get any wires crossed. I just got done test driving the car and the ac and heat work perfect. I hope this helps people out there to fix these problems without paying thousand of dollars to the dealer. I just fixed mine for free. Very satisfying.
  • rutrut Posts: 5
    In my 2002 highlander the air temp will vary with the slightest of bumps. It will jump from hot to cold immediately.

    The dealership wants $800 to replace the panel:( I'm thinking it is a loose wire or something.

    Anyone else seen this problem?

  • mikefm58mikefm58 Posts: 2,882
    Start reading posts backwards. Your answer is in there.
  • wwestwwest Posts: 10,706
    "...slightest of bumps.."

    Most likely a loose/intermittent connection to the OAT, Outside Air Temperature, sensor mounted behind or on the back of the front bumper just forward of the AC condensor/radiator stack.

    And open connection will indicate a sub-freezing OAT and the AC compressor will be disabled and the system will go into heating mode as long as the sensor is open.

    Another "bump", connection closes, AC cooling returns.
  • slowcarslowcar Posts: 59
    Problem description: in a hot day, the aircond only blows out cold air in the passenger side vents, warm air still in the driver side vents. The aircond was put in the recirculation mode; never have from the outside. My thought was that there was some thing (a valve, maybe?) blocking the cold air from going to driver side.

    What's wrong?


    Thanks all for help.
  • leean21leean21 Posts: 1
    ok, let me try this again, without hitting the enter button before i put a message....anyways, I just recently started having the problem of hot air blowing through while my ac is on, then switching back to cold air....i have tightened the nut behind the temp switch and am hoping that is the fix....thanks so much for all the guys are awesome
  • rutrut Posts: 5
    I actually took it apart and found a broken wire connecting the temp knob to the ckt board. It was a 3 wire cable soldered on each end. I removed the cable and replaced it with 3 individual wires. Problem solved.
  • I have same problem and tightened the knob. This has reduce problems but once in a while still get switch from cool to heat. How do I fix the broken cables? are there any specific instructions on how to do this?
  • I have same problem and tightening knot did not fix it. I like to try to solder wires. Could you please send me more specific instructions on how to remove ac unit? thanks.
  • rutrut Posts: 5
    You have to remove the complete unit out. it just kinda snaps out if I remember correctly. there is a circuit board that you have to remove. There are a few screws holding it in. Be careful handling the board as to not emit any static electricity that would take out the ic's on the board.

    You will find a small circuit board mounted where the temp control is. Go assuming you have taken the knobs off in front and removed the nuts on the controls, you can unclip the board and pull it out. There is a 3 wire cable connecting the circuit board to the temp switch. Mine had a broken wire at the small board. Be very careful trying to solder this back. It requires a small tip and not too much heat.

    Hope this helps. Better than spending $800 for a new one or $300 for a used one.

  • AlirobAlirob Posts: 17
    Slowcar, I have exactly the same problem on my 02 Highlander. Have you found a solution yet?
  • slowcarslowcar Posts: 59
    No...It seems like you and I were the only ones having this problem. It must be some thing very simple that prevents the freon from going to the driver side's vent. Hate to bring it in the dealer and spend $thousands$ .... Please post it here if you found some thing. Thanks.
  • rohoorohoo Posts: 2
    I have the exact same problem on my 01' Highlander. The temperature range is approximately 12-18 degrees warmer on the drivers side as opposed to the passenger side. I will let you know if I come up with anything.
  • Just wanted to thank the original poster regarding the ac temp issue and the loose nut. Just as you said, my husband took the knob off and the nut was loose. Boy am I glad I was reading this yesterday. It saved us a lot of money!
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