Heater quit... sort of

[wizzer]

My 2001 Highlander heat just became quite intermittent. I have the manual temperature control version with the 3 knobs, not the automatic climate control. There is just one little place on the dial where the heat comes on full blast. It seems to move around and the heat will work for a while then stop. Then I adjust the knob around and find the hot spot and the heat works fine for a while. Except that it is full on. The fan works fine and the control for where the heat is directed also seems fine.

Anyone with experience with this? Is there a part I can replace? Does the dash panel around the heater radio, etc remove easily? And if so how? Anyone know of a reasonably priced source for any parts that I might need?

Thanks

[MMitsock]

I have an '03 Highlander. Although I haven't had the dash apart, I think the heat and AC is all controlled electronically. By that I mean there are no cables connecting the knobs to a valve or duct door, those knobs set by an electronic signal to a motor that opens the ducts or in your case opens and closes a valve allowing coolant to the heater core. Personally I don't think opening up the dash will allow you to find any parts that can be replaced easily, I think you may have to bring it to the dealer for a diagnosis. It may require replacing the electronic controls in the system or the small motor that positions the water valve on the heater core.

[jboucher]

I may be having a similar problem with my 02... I seem to have the same symptoms, heat full blast all the time, yet the fan and directional controls (up/down, defrost, etc..) work fine... Except today when I noticed (quite by accident) that if I moved the temp dial a notch, I would sometimes get cool air shortly back to full heat... moving it a few notches sometimes changed the temp...

Did you have it diagnosed at the dealer? Sounds a lot like the problem I'm having... It started just after a dealer oil change (coincidence?)

BTW... davidj92 recommended me to this forum...

[wizzer]

OK. I solved my porblem. Here is what hapened. The nut that holds the temperature control to thee front panel came loose. The knob and control started to wobble. This stressed the wires on back. Eventually 2 of the 3 wires attaching the temperature control to the cotrol circuit board broke. When the control knob was in certain positions one or both came into contact and the heat would come on.

I went to the dealer and they said "replace the heater contol unit." It costs $ 586.00 plus labor. I bought one from a junkyard for $ 75.00. I removed the bezel which surrounds the whole unit by gently prying it with a couple of screwdrivers. Be very careful not to sccratch the dash. Once that I saw that all connections to the back were electircal (3 plugs) I removed the old one. I opened it up and saw the broken wires. I soldered them, reinstalled it and it works fine now.


Pictures attached.

[knobc01]

This sounds typical of the Highlander. The heater on my 2002 has been intermittent lately. Thanks for the insight.

[sbl]

Thanks wizzer! I just did as you suggested on our 2001 Highlander and it works like new. I had the same problems with intermittent heat and fiddling with the control and sure enough it was due to the the broken wires. Good work.

[dfluitt]

Hi Wizzer. The Toyota dealership here in Santa Rosa California charged me $55.00 to diagnose my Highlander's heater problem. They said they would have to order the part and I could bring the car back next week to get it fixed. I asked him how much it would cost and he said that he was embarassed to tell me that the heater control unit was going to cost $681.00 dollars to replace. After I picked myself up off the floor I asked him if that included labor. He said the labor would be another 165.00. The total to fix the car? 55 + 681 + 165 = $901.00!!!! And this doesn't include tax...
I did some research last night and came across this site and your post. It took me all of one hour this morning to pull the control unit out of the dash, open it up, solder in three new wires, and put it all back together. It works Great!!
I took my wife out to the movies tonight to celebrate the money we saved. I think the most satisfying part will be tomorrow when I call the dealership to cancel the appointment to have the car worked on.
Thanks again for your taking the time to post your Highlander experience here.
I took several pictures of the insides of the heater unit showing the before and after of the broken wires and the fix. I can post them here if anyone wants to see what the circuit boards look like and where the wire needs to be soldered.
Thanks again.
Don

[bob259]

...........I took several pictures of the insides of the heater unit showing the before and after of the broken wires and the fix. I can post them here if anyone wants to see what the circuit boards look like and where the wire needs to be soldered.
Thanks again.
Don

Yes Don, please post them.

[dfluitt]

Here are the photos documenting the heater control fix. The first shot is of the panel with the knobs removed. The nut that comes loose is under the knob and holds the shaft steady. The loose nut allows the small circuit board behind it to rock back and forth when the knob is turned causing the wires to break.
The second shot shows the back of the heater control unit with the cover removed showing the main circuit board and the small circuit board (circled) on the back of the control knob.
The third shot shows the ribbon cable where it breaks off at the solder joint on the small circuit board.
The fourth shot shows the three wires I soldered in place of the ribbon cable.

[peid]

Nice photos dfluitt! Thanks for posting them to help all the members out. Also, welcome to the site, glad you found us!

[jimdejet]

Wizzer, Thanks for sharing your problem and fix. I have an 05'. After reading your post I checked my tmeperature control knob. It was very loose. It took at least 2 1/2 turns to retighten. I put a dab of fingernail polish on the nut and external threads to help prevent loosening again.

Thanks again, you have just prevented a future headache.

[nvongunten]

Thanks for the help dfluitt & wizzer. I am new to this site and this may have just saved me a lot of money. I appreciate the help and this website seems to be very helpful.

There is no way the engine would have come on because of this, correct? My engine light popped on right when my heater quit working. I took it to an auto zone to have the free diagnostic test run and it threw no codes. It actually just went off but came back on this morning.

I appreciate any help.

[wizzer]

Sorry. No ideas about the engine light being related to the heater.

If I recall correctly, I was told by the dealer that the amber check engine light is frequently related to the Oxygen / O2 sensor. The Highlander has two and one of them is more likely to fail than the other.

If I recall correctly it costs a couple of hundred dollars to replace both and I don't know if it really does much good. If I recall correctly it just adjusts the fuel / air ratio during warm up so you might use a bit more fuel.

[PineRidge]

My 2001 Highlander heat just became quite intermittent. I have the manual temperature control version with the 3 knobs, not the automatic climate control. There is just one little place on the dial where the heat comes on full blast. It seems to move around and the heat will work for a while then stop. Then I adjust the knob around and find the hot spot and the heat works fine for a while. Except that it is full on. The fan works fine and the control for where the heat is directed also seems fine.

Anyone with experience with this? Is there a part I can replace? Does the dash panel around the heater radio, etc remove easily? And if so how? Anyone know of a reasonably priced source for any parts that I might need?

Thanks

Your problem is most likely one of the servo motors located just behind and to the left of the glove box or the main control with the 3 knobs. I puleed the glove bow in less than 5 minutes.

In my case it was the latter and I contacted a auto recycler to acquire a used part. Toyota wants $650.00 for the dash control. BTW get your fingernails or a small screwdriver under the trim as it pops off, without screws.

[edwardh1]

Wizzer, Thanks for sharing your problem and fix. I have an 05'. After reading your post I checked my tmeperature control knob. It was very loose. It took at least 2 1/2 turns to retighten. I put a dab of fingernail polish on the nut and external threads to help prevent loosening again.

Thanks again, you have just prevented a future headache.

Hey Jimdejet
does the knob just pull off?