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.

 

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...

 

Heat problem solved

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.

 

Highlander Heater

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

 

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.

 

Re: Heat problem solved

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

 

Re: Heat problem solved

...........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.

 

Re: Heat problem solved

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.

 

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

 

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.

 

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.

 

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.

 

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.

 

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?

 

Just completed the above repair on my girlfriend's '02 Highlander. Was done in about 45 minutes, saved about $800 bucks from what the dealer quotes for the repair. Great pictures and repair description. Great website, looking to contribute when I can.

 

Just completed the above repair on my girlfriend's '02 Highlander. Was done in about 45 minutes, saved about $800 bucks from what the dealer quotes for the repair. Great pictures and repair description. Great website, looking to contribute when I can.

have the same problem on my '03 but am totally clueless about cars!

there is a big plastic 'frame' that appears to be covering the edges of the plastic frame that goes over the radio and heater controls. does that just pop off also? and do I have to take the knows off of the heater control? do I just pull them.

while it is annoying to have to 'fish' for the click that gives heat or cold as I spin the temp control dial, it will be worse if I break the thing totally. (although perhaps not as bad as the $750 that the dealer is asking to put in a new one. they will also 'repair the old one' for $300 which I might end up having to have done).

skiguy,

 

I have a 2001 so my knowlege may be incorrect for your model. I believe that the knobs just pull off. The large plastic bezel also just snaps off. A couple of screwdriveers slipped under the edge worked for me. Be very careful not to scratch the paint. Some electrical tape around the tip of the screwdriver may help. Then you should have access to the heater control.

Read the other entries for more details and pictures.


Wizzer

 

Re: Heat problem solved

Thank you so much for posting the info and the photos. I had the same heater problem with my 2001 Highlanderr. Because of your posting, I saved $600 plus tax plus the cost for labor. Wow!!!

 

You guys rock!!! I started up the heater for the first time in since the spring and found no heat. That happened on the way to work and it is now 11:30 in the morning and the problem is fix. For now anyways!! When I got to the temp control panel and located the wires coming off of the temp control switch they were broken. A quick solder job and I have heat. I reallly want to thank you for adding pictures it helped me alot.

 

You guys are geniuses! Exact same problem ('01, intermittant heat, found 2 ribbon wires were broken, etc.).

I had two big differences though: 1) all knobs were tight (but the wires were broken anyway), and (2) after fixing the broken ribbon wires I get perfect heat on the passenger side, but only cold air blows on the driver side.

I would have guessed that there would be one servo valve on the heater core would work for both sides at the same time - It does not make sense to me that Toyota would have gone to the trouble of installing a separate valve for each side if the two sides can not be adjusted separately.

In any event, I have to get heat to the driver's side somehow. I get the same amount of air blowing on both sides, but only one side gets any heat. I wonder if there is pair of flaps on the heater core that each open on command, and in my case one is not getting a command? If this was the case, I wonder if I could override the driver side flap to let the heat through - I would not think it would be a problem, but is it possible to get at it?

Does anyone have any ideas?

Wizzer - do you still have that heat control head part for $75? (it seems that I might have to replace the assembly to fix this problem after all, and the wreckers are now asking $250 for the part)

Tim

 

You guys are geniuses! Exact same problem ('01, intermittant heat, found 2 ribbon wires were broken, etc.).

I had two big differences though: 1) all knobs were tight (but the wires were broken anyway), and (2) after fixing the broken ribbon wires I get perfect heat on the passenger side, but only cold air blows on the driver side.

I would have guessed that there would be one servo valve on the heater core would work for both sides at the same time - It does not make sense to me that Toyota would have gone to the trouble of installing a separate valve for each side if the two sides can not be adjusted separately.

In any event, I have to get heat to the driver's side somehow. I get the same amount of air blowing on both sides, but only one side gets any heat. I wonder if there is pair of flaps on the heater core that each open on command, and in my case one is not getting a command? If this was the case, I wonder if I could override the driver side flap to let the heat through - I would not think it would be a problem, but is it possible to get at it?

Does anyone have any ideas?

Wizzer - do you still have that heat control head part for $75? (it seems that I might have to replace the assembly to fix this problem after all, and the wreckers are now asking $250 for the part)

Tim

 

Sorry it is long gone. try ebay

Wizzer

 

Re: Heat problem solved

OUTSTANDING! My wife told me today that the heater in the Highlander worked sporadically. I found your post and it was exactly the problem. It took me about an hour to get to the wires, but sure enough, two of the three had snapped. I soldered on some new stronger wires, put it back together, and it works! I'm sure that this saved me several hundred $$$. Thanks again!:ts:

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.

Anyone want a Heater control unit for a 2001 - 2003 Highlander for $ 75.00 plus shipping? It comes with the balance of the 30 day warranty.

Pictures attached.

 

add me to the list... my wife has been having this problem for at least 8 monthson our '02 highlander. she found if she gave the dial a smack it would work.

i just joined this board and read this thread yesterday. followed the fix and it worked perfectly

wizzer = genius !!!
:tu:

 

don't smack it .It is too delicate...the whole panel and board costs too much.


BUT, excelent thread.