Toyota Highlander Heater Control Head Repair

I got a call today regarding the repair of the heater in our 2003 Toyota Highlander. They wanted $850 dollars to get things working again; almost $700 of that was for the "heater control head." 

Background: we've had problems for years where the heater would come on, full blast, and would only turn off when we rapidly jiggled the thermostat control. We mentioned it many different times when bringing the car in for routine maintenance and were always told "can't fix it if it ain't broke; bring it in sometime when it stays broke." 
So as we're chatting I reminded the dealer of this history. He took a little off of the price so I told him to go ahead and order the part. I mean it's almost winter. In Kansas. A heater is non-negotiable. And to their credit they were going to give us a free loaner overnight as the part had to come from Kansas City.
But then I got to thinking. I know that on occasion Toyota has had systemic problem with different functions on various cars over the years. I googled "highlander heater control head (HCH)"; and the very first entry led to a web forum where there were 21(!) pages of discussion about the broken heater and how it could be easily repaired.
All of the discussion and photos led to the realization that this was something I could do myself! I called the dealer and had them cancel the order for $700 part. I then spent 40 minutes removing the broken HCH, too long soldering the broken wires back in place (hey, it's been a while) and then less than 20 minutes reinstalling everything (not counting the time spent looking for the lost nut!) 
What's going on is a design flaw, pure and simple. The thermostat potentiometer (pot) is connected to the logic board by 3 short wires. Did I say short? They are so short that if the pot moves, even a little bit, one or 2 of the 3 wires breaks off.
There's no excuse for such a shoddy design.
Anyway, to wrap things up, I had to replace the lost nut with one from my Fender telecaster volume pot (thank you Leo Fender!), but the car is put back together and both the heater and air conditioner are working fine. 
And you know, the thing is that after a while it wasn't about saving the money. It was about not spending $800 dollars to solder 3 lousy pieces of wire! Here's the link to the first page of discussions about this well known problem (how well known? Well, why do you think they didn't fix the problem when the car was under warranty? Uh huh, I thought so):
Here are a couple of pictures showing the broken wires and one of the gaping cavity in the middle of the car while it was being repaired:

Highlander heater control

Highlander heater control

Highlander heater control

79 thoughts on “Toyota Highlander Heater Control Head Repair”

    • The thread that keeps on giving……I had replaced the t-stat and still no heat. I found this thread/post and had the exact issue. I went to hobby lobby and purchased a pin point tip soldering iron and repaired the pot in 5 munutes. It did take me another 20 minutes to repair the 24 pin cable that I pulled off the board…….ouch. Be careful. The cable removes from a connector on the secondary board(you can see it through the window they have in the plastic. Great post. It saved me $700. Thank you.

  1. You are brilliant…. You saved my a ton of cash…. you were absolutely correct and when I showed the mechanic your pictures and information, he said you were right on! Appreciation to you! I have had this issue for two years and it was getting HOT!

  2. I’ve had the same problem on a 2004 Highlander. Following the advice of a friend, who followed the advice of a friend, I simply loosened the nut and the heat began working again. I did not take the HCH out. I never believed it would work but it sure did. I’m guessing my wire or solder joint isn’t completely broken yet and loosening the nut a tad improved the connection(for the moment).

  3. I had the same problem, heat pouring out and NO air in the middle of summer (95 degrees) while going through menopause. Lets say NOT a pretty picture. Pulled off that knob and yanked off 3 of those wires on the HCH and air conditioning works, no heat though. I will need to solder those wires back on now that it is getting cold, but no problem I am sure it will work.

  4. Thank you mike! Your picture help me find the location, the broken wire is at the back we must uninstall the knob to see the location.

    If someone don’t know how to remove the surrounding cluster panel (like me to learn from a mechanic) , just use a flat screw driver plug from the rim of the cluster to pull out.

  5. thanks for the help. that is what is was. got no help from local dealer. they just want to sell you $850 part.

    • I would guess that one of the wires is still not making a good connection.

      I say that because the original failure mode is: broken wire, all heat, all the time. And then eventually, no heat at all.

      • Well, now nothing works but the blower. The main ribbon of wires on the board came out of the long black holder. I have tried to put them in the holder and it looks like they’re in.I have tried 6 or 7 times but nothing happens. Looks like I need a new or used controller. Anyone know where I can find one?

        • Don’t know if you got this fixed but if you squeeze both ends of the black ribbon receiver, it will come up just a little bit.By insert the ribbon all the way down and press down on the black ribbon receiver (it should snap into place). Don’t know if you were already doing this, ran into the same issue but this fixed mine.

  6. Hey Mike,

    Thanks for posting your link/page for the Toyota heater control.
    I was wondering what setting you used on your soldering gun, & what type of sodder you used, or did U just heat up the existing solder on the board of the thermo switch? Thanks, Jeremy (2002 Highlander)
    ps. Toyota outta be sued for a class action lawsuit for well known design flaws and fleecing their customers at dealerships for $800+ per rip off repair!

    • I used generic solder I had lying around and set the iron to a medium heat.

      I agree re: lawsuit, but pursuing that would take considerable effort.

      • yes a class action lawsuit is in order. This problem covers all Hilanders from 2001 through 2007. It also encompasses the T100 truck and other Toyotas. Take care, Bob Myrick.

  7. my quote today in atlanta ga was $1068.45 not sure if i can do this my self
    BUT the dealer will never see me again

  8. This totally saved the day! I just bought my gf an 05 Highlander , only to find out last night that the heat wasn’t working. Found this article and was able to solder it myself. Again, thanks for saving me the moo-la!

  9. I thought I hit a “gold mine” in finding this. Then, I carefully soldered the three connections only to go from just the heater malfunctioning, but at least having one and everything else to:

    NO AC, No hazards, no rear or side mirror defroster, no clock, nothing but a heater that now works.

    I’m beside myself. Any ideas what I might have done? I also checked all the fuses and they’re o.k.

    • EdJ – if you ever get this message, please let me know how your problem was fixed… I’ve got the same problem. Thank you!

    • I also had the unit repaired just to find that now the heat works but the AC will not work. Any news on what might be the cause?

  10. As a Toyota Service Advisor, I am floored that other dealers are not explaining to you guys what is going on- I have never repaired one myself but am aware of this and having had my mother in laws fail I went searching on how to fix for her. I often explain the theory behind why it fails to my customers but as a dealer due to liability reasons we cannot fix them.

  11. Another question, is this a fix for not being able to change the degree setting up or down with the control knob, my nut was loose behind the knob, so I’m thinking it is.

  12. Yikes-I’m comforted that I’m not alone with this problem in my 2002 Highlander. I’ve had the heater/cooler problem “fixed” a couple times at the dealership and now it’s acting up again.
    Any movement on a class action suit? Thanks!

  13. I want to thank you for posting this information. I have a 2002 Highlander. This past winter my heater wasn’t working correctly, periodically my husband would find heat but as soon as I would hit a bump it would be cold. I dealt with that for the winter and wasn’t going to do it again this winter. We took my vehicle to the shop and the mechanic ordered the knob thinking that was the problem. Well he found out it wasn’t and said that my vehicle needed the whole heating control housing and he could get it for $600. I was looking online and came across your blog and printed it out. My husband took the print out to our mechanic and low and behold 2 of the 3 wires were no longer soldered the the circuit board. Our mechanic soldered them and I now have heat in my vehicle again. If I wouldn’t have found your blog it would have cost me over $700 to have this issue fixed instead of $50. Toyota should let people know that this can happen and it is an inexpensive fix instead of people replacing the whole heating unit for a small fortune. I thank you so very much for posting this info.

  14. I have what seems to be the same problem with my 2008 Highlander, but the steps to remove the trim panel (or whatever you call this plastic) around the climate control to get access to the problem is totally different for the 2008 than it is for 2001-2007. I can’t find any instructions for removing this trim. Can anyone give me some guidance on this?

  15. I have a 2007 Highlander and the ac was working fine until a puff of white smoke came from the middle vents. For about 3 months I have had no ac and no heat. The Toyota dealer said it can be the head unit or the ac evaporator. To true find out It will cost $300 to dio it and what ever the cost of the repairs. from $900 to maybe $3200 for a new ac unit. The sad this is just came out of warranty and there is only 56,0000 mikes on it.

  16. Thanks for the great info. Having the same problem here in MN and hope to have it fixed per the clear instructions here.

  17. had the identical problem with 2001 Highlander.
    thanks to this internet discussion and soldered new wires where there were 2 broken. saved $1000.00
    thanks again.

  18. I am currently a tech at a toyota dealership and figured this solution out about 3 years ago. I have applied this repair to a few people and had issues with my manager getting upset. I told him that a $100 try would make alot of people happier than a $800 repair but he wouldn’t go for it. I do have a couple panels that i have fixed, thinking about putting them up for sale

    • If you would have one that would work for a 2002 Highlander I am Interested. I am In Va. Please advise either way. Thanks, Bob Standard AC/Hea/ not auto… 4 cyl. cheape Highlander if there ever was.

  19. Hello!I own a 2005 highlander I have heat on the drivers side but cool air on the passenger side.Any idea what this problem could be!!

    • Hi , was wondering how you made out with the A/C problem. I have an 03 highlander with same problem, hot air on driver side and cold air on passanger side.Any info. would be appreciated

  20. I had the same problem with my 2003 Hylander. I followed your instructions with one deviation. I drilled out the three terminals using a 1/16″ drill bit and dremel drill. Carefully striped ~1.5mm of wire from the wire rope placed the 3 wires in the holes and soldered them in place. My local Toyota dealer wanted $850 just for the part a local used parts yard wanted $350. It took a few hours but was fun to find it worked. Great advice. A reason why these wires broke is the heater controller lock nut loosed over time and through movement of the controller assembly over time the wires broke.

  21. My 2004 Highlander is getting fixed by me today.It happened last year, i tightened the nut on the pot, today the heat was on and I will take it apart now. Nice design Toyota.

  22. Having the same problem…..carrying the printed instructions to my mechanic buddy tomorrow to fix. I’m sure I will have less than $100 in it. Toyota said the “part” was $730 + tax…….WOW!!!!!!!!! Once fixed….I will carry instructions to Toyota Dealership and ask them why they don’t “just fix it”??????? I’m sure glad I have a high school buddy that is a mechanic and can do these types of things.

    • all that needs to be done is Google the natsb and find the complaint section. enter your complaint. there is no minimum number, but if we all complain we may win. I may not have the letters correct but it is easy to find.

  23. iam buying a 2003 highlander off my brother who just took it in to toyota dealership with this same ribbon problem-they wanted $2500 to fix

  24. Followed instructions from this blog and heater is working again. To help others for helping me, here’s how it’s done on a 2005 model. To tighten knob screw, just pull the center heater control knob off with your hand and tighten. If you think the wires are broken, continue to read. To remove panel, start around bottom with screwdriver just enough to get the corner loose. Then use your hands and screwdriver to gently remove the panel. Remover 6 large bolts. Watch out for gold metal thread clips. They will fall and you can’t recover them. If loose, remove and squeeze slightly with pliers so they will be tight by friction. Unscrew six Phillips screws to separate heater control from bracket. Remove three wire harness plugs. On a table, unscrew 8 phillip screws from heater control box. CAREFULLY, use small screwdriver to unlock ribbon plug similar to a PC. Remove cover. With the heater knob off, expand plastic clips and pull from hole. If one of the wires is still soldered, it will stay in place. I had to solder both outer wires. I used small solder iron and regular solder. Reverse these procedures to reassemble. Make sure you relock the ribbon plug! There is a small black clip on each side. THANK YOU!

  25. My mechanic use to work for a ford dealership. He said if ford had a manufactoring problem that they would have a recall on any car that had the kind of problem we are having.

  26. I have 2008 Highlander. The blower does not run. I checked the blower fuse in the fusebox and found good. The speed signal (red wire to the heater) is good. but does not have power at the blower end. Is there any relay or control unit between fuse and blower? I checked the heater unit and blower (both are good).

  27. Thanks for the information, I just bought, used, an 06 Highlander, and the A/C works great, but when I turn the heater on all we get in cold air. It’s like the A/C won’t shut off at all. At least now I have a starting point to find the problem.

  28. thank you this is exactly problem with the car. i think Toyota should make a recall on this you help a lot with the pictures again you are a life saver thanks

  29. Hi Mike, mine is a 2006 HiHy with a in dash display for climate control. I get AC but the heater is not working. Suspect something simple like yours. Any thoughts on how to debug the display model? thanks!

  30. Heat went out but Airco OK. I finally fixed it, following your instructions.
    It was the Wire. Now both Heat and Airco work again. Thank you for your
    documenting this procedure. You saved us a bundle!

  31. 2005 Highlander Been having the same problem for a couple years.Could not control the heat or air.It was intermitten until recently ,It went to full hot and stayed their. ,I took it to the Toyota dealer and like all the others.$800 to replace the module but my dealer wanted $400 to do the solder job.I found that if I folded a small piece of paper and stuck it under one side of the temp. cont. knob,It would cool but of course that was very temporary until we could permanently fix the problem.We Googled and found this and I took the first step of tightening the nut under the control knob with a socket and for now it is working normal.Took two minutes .This website has been so very helpful.Thanks to everyone that has supplied info.

  32. My husband did this fix last year and it was fantastic. My heat just started to fail again so we checked and the soldering is fine and all seems good on the circuit board. What else could be the problem?

  33. Tried to repair my 2004 today. Problem, cannot get two of the three wires of the switch to solder to the control board. Anyone know what wrongs?

  34. I am shipping my climate control unit to a company to have it remanufactured. $15 to ship to them, $15 to return. $35 bench fee if no problem found. $159 reman fee if they fix. I’ll let you know how it all works out. Sidenote, I did not find any broken wires at either switch.

    • Dominic – did the remanufacture via shipping work out? I am looking at doing similar. Or does anyone know a mechanic in Portland OR Metro who works on this issue? My mechanic said $850 for a new unit.

  35. Just read the above and shared the frustrations with the heater control issues. I went out to the vehicle(2004 highlander), removed the center control knob, and sure enough, the potentimeter(pot) was loose. Using an 11mm socket, I carefully hand tighten up the nut and tried the a/c. To my disappointment, it was still putting out warm, but not hot hot air. Tried again and this time by pushing and holding the pot slightly to to right (use your right hand) I tightened the nut using the index finger of my other hand, I was able to get cold air. I then hand tighten the nut with the 11mm socket. I got lucky this time but. I Would suspect that over time the unit might loosen up again. This is because there is not a locking washer under the nut to keep it moving due to the torque properties of the knob/pot mounting arrangement.

    My thanks to all for the inputs

  36. Note to all*** to avoid breakage release the bezel on dash by pulling at the widest points first from the inside of display with finger nails or the outside with a credit card. locking tabs would be at 10 and 2 , 8 and 4, 7 and 5 o’clock more or less.

    Check wiring at all control knobs and test for continuity. I found 2 of 3 broken on my heat selector and 1 of 3 broken on my speed selector.(2005 Limited) The switches are the same internally on a Highlander Limited.
    I used about a 22 gauge single strand wire and needle tip iron, with RADIO solder (with resin flux). I do not recommend Cat 5 or telephone strands because if you strip them wrong you knick the copper and it will weaken and break. I do recommend leaving a bit of slack in the new wire. I did this with a mini coil which I wrapped around a finishing nail.
    As for the main multi strand ribbon wire be VERY careful to engage it fully and depress the plastic clip to lock to the board once done. Easy fix, but be patient, don’t try this with a soldering gun unless you have a special touch and a very fine tip.

  37. I’d like to first humbly thank the Lord for Mike maintaining this blog. It was source of inspiration to see there
    Is answers and guidance to be self suffient. Thank you for providing knowledge to complete this task and
    Most of all, the ability to be cost effective and saving me huge amount of money!

  38. I have a used 2004 Highlander that blows hot or cold air whenever it decides to. No ryme or reason that initiates it. If I fiddle with the knob it may come on for a few minutes but could go off any minute. By reading 100’s of posts of the same problem and same years of vehicles, seems it’s a manufacturing defect. I will not pay hundreds of dollars for something Toyota should be repairing for free. Winter is coming upon me know as I live in Wisconsin. My Toyota dealer I’m sure will not acknowledge the common but very important flaw in these vehicles. I just took it out there as all my dash lights are on, ABS, tracking, brake, tire
    pressure light flashing. They said it was a sensor and hub repair for over $700 dollars. i got a feeling it was not that but could be. Decided to take vehicle before they repaired it but still have the same problem. As I read other people that have had the same problems with this year vehicle, it’s quite disturbing. I have had 2 Toyota’s in the past and drove both over 200, 000 miles without any problems except normal maintenance. I am contacing Toyota and if they do not acknowledge the flaws in the vehicle, I am reporting them to the Better Business Bureau. I will not pay near $2,000 total for both problems, which is evident is not uncommon for this year and many other years near this one. I am single widow and am unable to repair myself and shouldn’t have to considering what sounds like it should have been recalled for these two issues as there are so many. Wish me luck.

  39. My 2005 Highlander has been doing the on off heat and AC for a few years. I asked the garage and they said probably $800+ to fix it because they would have to tear out the dash. Over time I realized that when I held my hand on the heat knob, pressing down lightly, the heat/AC came back on. So being a woman, and having no mechanical skills, I got a piece of thin cardboard and put it at the top of the knob so that the knob is tight and held down toward the floor. This has worked for me for 2 yrs.
    However, now I am getting heat in through the vents even when the heat blower is off and the temperature knob is turned to cold. Heat comes out of all my vents, this is fine in the winter but in the spring and the fall, it is too warm.
    If I get the garage to solder the wires will that stop the heat from blowing all the time?

    • I’m glad you found a fix that worked for a while, but can’t say for certain if soldering the wires will fix it, though there’s a good chance.

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