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Thanks to the information found here and Wizzer's instructions, I was able to repair my 2002 Highlander's intermittent heat by installing new wires between the knob board and the controller board. It saved me $1100 the dealer was going to charge me to replace the entire module. I figured the module would be a black box under the dash, but it is the whole darn center console minus the radio!

It was easy for someone who has soldering tools on-hand, but you need small diameter wire, a steady hand and probably a magnifying lens and light to be sure you don't leave solder trails between the tight contacts on the two circuit boards you will solder.

I took the posts from the link listed in previous posts and showed the pictures to the dealer service agent. He was able to let me talk to a service tech who told me this fix would not last but a couple of months and that I should replace the module. I beg to differ, I tightened the nut on the knob which stopped the wobble that allows the wires to flex and break. I followed the tip above to put some nail polish on the threads before tightening it. This should prevent it from working loose again. The tech said the replacement module is constructed differently to prevent this in the first place. I've read all the above posts and get the impression some think that tightening the nut is the solution to the AC/heat problem. That prevents it from getting worse, but if you are experiencing the problem, tightening the nut AND making sure the 6 solder connections are intact is necessary.

When I was arguing the charges with the service agent, he said their techs could not solder anything, they can only replace entire modules. Now that my Highlander is out of extended warranty, I can't imagine there is any reason I will ever set foot back in their flashy facility again. I had it in three times for the same problem that is obviously well-documented here and must be in Toyota's own database and they could not solve the problem until the fourth time when they decided it need to have the center console module replaced (1000 miles after the extended warranty ended of course, sounds fishy to me).

I argued with them (nicely) that I had found 30 people on this website (I printed all of these comments and highlighted them), who knows how many other websites have other people with the same problem, but the common thread is the 2002 (+-1 year) seems to experience the problem and the solution is $1000- 3% of the cost of the entire vehicle! They said they have no authority to waive the cost of the replacement part, but gave me the toyota help line where I could complain. 800-331-4331. Now that it is fixed (by me), it seems that it is pointless to call, but I will so maybe the count will reach a critical mass at which point they might trigger a recall. I'd encourage everyone else who had this problem to call too.

There seems to be a lot of evidence this was a design defect and $1000 is considered grand larceny if you had pick-pocketed YOUR neighbor, why should the auto companies be able to saddle the consumer with a similar debt. I bought this vehicle due to rave reviews it was getting in 2001 and 2002 for reliability and high service marks. I will say it has been very reliable, but I've been trying for a few years to get this problem fixed, so I would say the service marks are not quite that high!

Good Luck everyone!

T  

I have a problem with a 2002. My wife locked her keys in the car and had someone help her unlock it by slipping something in the window. After several attempts they finally got it but now the window will go down by itself without the car on or anyone in it. Replaced the master switch but you can still come out at times and there the window is, down. Maybe someone has ran into this problem.  

Iceman 138,

I want to thank you for your post on the forum. I also had a problem with the heater control unit and was quoted by a repair shop of around $1000 to replace it. When I dismanteled and took out the control unit I noticed that a soldered joint had come loose. I didn't know if I could of done it when pulling the unit out but I had my electrican friend take out the ribbons ( temperature adjustment and fan speed ) both and solder back in three separate wires on each side. I figured if the one side gave out because of the torque to it than the other side was not that far behind.
When he got the unit back to me the next day I put it back together and said a prayer ( a real prayer ) and what do you know ( Thank you Lord and you too Iceman ) the complete unit was working fine.
I do understand that the repair shop was using its best jugement when they told me what needed to be done. For them to take everything apart like I did would have been above and beyond their call when they really had no clue like I did because of your post. Thanks again.


                            Chuck Powers  

I have a 2004 Highlander and have had the same ac/hot air blowing problem. The dealership wanted a fortune to repair. I had a neighborhood guy try to fix it, but it would cost a lot to order the part. But he said he could rig it to blow only cold air without replacing anything. He did something under the front passenger side dash. I think he was disconnecting a wire or something-whatever he did it worked. Of course came winter and he re-connected or whatever, so I would have heat. The following summer I took it to Tires plus to have them repair it-over $700. Now a summer later and I have hot blowing air again. Does anyone know what the first guy connected or disconnected and how do you do it? Please help-I'm menopausal and must have a/c and I can't/won't pay that kind of cash again. Thanks  

iceman138:
Hi All, don't ask me how I stumbled upon this thread, but I had the exact same problem with the heating system a few months ago and could not find any useful information on it.  I have a 2003 Highlander (non-Limited) and was rear-ended.  When I got the car back from the body shop, it would only blow hot air.

I took the dash apart and removed the HVAC control unit to see if I could figure out what was going on.  I had noticed that the retaining nut that was holding the temperature knob in place had come loose, so I looked there first.  It turns out that the 3-wire ribbon cable that they use to make the three connections from the knob (potentiometer) to the circuit board had gotten brittle and cracked, in effect disconnecting the knob from the circuit board.  I soldered 3 new wires in and it works great again.  

It's just a very poor design by whoever made this unit.  I think the wires are pretty frail to begin with, then the knob got loose, and the rear-end collision was probably just enough to snap the wires.

If anyone has any questions, feel free to let me know.

Was it making a wierd sound over behind the glove box?  

OMG !!! Thank you so much 4 that info, we run a small body shop in oregon the 02 toy Highlander was here for a deer hit ,putting the car back together checking the ac and we discovered the switch was loose and not working ,  so we checked online and saw your post, well we did what you said except we used the existing wires and soldered, works great!! The best part is we knew it had to be "like that before" or just happened at the shop, any case customer will be happy! especially if they already got a quote from the dealer to fix. Thanks again ,  Acam  

I also have a 2002 Highlander and my air comes out cold for a few seconds then goes to hot air - even when no dial is on hot air comes out. They are telling me its the heater control housing unit but i'm not sure. I would be interested in seeing if everyone replace this part and theirs works fine now or did you just got in the back of the dashboard and check the wires to see if they came off like some other people are reporting.

Thanks so much
Debbie  

I have a 2001 Highlander whose air went out a couple of years ago. The mechanic, not a dealer said the unit was shot and replaced it. (Whatever that meant). Expensive. This week blinking light, cold then hot air, and the dealer just told me $1700.00 to replace the compressor, flush and dry the system because metal pieces are throughout the system.I'm taking it to another mechanic for another opinion. A gasket sprung a leak a couple of months ago trashing the air fuel ratio sensor.That was a day after I had the serpentine and couple other major belts changed. I asked the guy how much I had spent since Jan. He didn't have time to look it up.  

At 180,000 miles my engine melted. I had bought it new and had regular services done like I was suppose to. I took it to my mechanic. He said he had never seen anything like it . He even called Vallejo Toyota to ask them what they thought had happened. They were clueless and really didn't want to account for what had happened . The engine became so hot that the bolts that held the heads on the engine melted their threads off . My mechanic who has a well known history for working on high-end to custom cars could not fix it and couldn't find anything else wrong with the car. It cost about $5000.00 to replaced the engine. My mechanic could only concluded that it had to be a factory defect.
   I have also had another problem with the computer on board that gave a false reading and cost me $982.00 of which Toyota had to reimbursed me but I had to empty my bank accounts just to do that.  

How difficult was it to remove the HVAC Controler Panel?

What if the pot is bad or broken can it be rplaced by anothe how many OHM is it?


cbateman@usa.com  

There is no doubt this is a problem with these vehicles.  I have a 2002 and this same exact problem happened.  It cost me $600 to have it repaired.  The garage I took this too was told by the Toyota parts manager this is a well known problem with the Highlander.  shame on Toyota for not issuing a recall on this.  

Hi...
I'm having almost the same problem some months ago.  The AC was going hot and cold temporarily and if I touch the knob it turned cold again.  The problem was not ocurring constantly.  Some weeks ago I noticed that the heater knob is loose/looks like is break.
How did you take the dash out to repair?
I really appreciate your help.  

I too have a 2002 Toyota Highlander. 79,450 miles on it. Just had a few sensors changed thru Mienke, engine light went on again so we decided to bring to Toyota dealer. They put it on the machine and the code came up that it was another sensor. Meinke also told us that our cadilitic converter could possibly be going, Toyota says this did not come on the reading. This can be replaced free if under 8 years or 80,000 miles. They best not be telling me a fib and have something happen after the 80,000 miles. But lately I have been having the same problem with the heat. I will turn it on and it will blow cold air then put it full blast and turn down and it will blow hot air. Happened a few times. Hate to put a lot of money into. Had the car this long and never had any issues with it. Normal wear and tear. Really love the car but now having to put money into is becoming bothersome. Need this taken care of where we live in the northeast, where it gets pretty cold in the winter months.

Would really be interested in if there is a call back on these models.

Almost feel like turning it again but with economy it is tough.

Hope to hear some more information on this in the future.