Have you checked the coolant level? If the level is too low it'll affect your heating system, especially if you're going up and down hills. If the cooling level is fine, were you going through hard turns and/or a winding road when the cooling occurred?

TrailDust

 

That was my first comment to my wife...possible low coolant. So I waited until the next morning when the engine was cool and checked it. Wasn't low in the reservoir and was at the top of the radiator too.

I thought maybe it was low on coolant because we were on a windy road heading to the freeway. But then it happened down in the city at a stop light. It will be interesting to drive it more and see if it happens again.

 

Is the Heat knob loose? My wifes 04 done the same thing and once I tightned the knob up real well it fixed the problem. Do a seach on here about the problem I think it is a common one and you should find some informtion on other possable fixes if tighting the knob doesn't do it.

 

Thanks! That fixed my 2005 HL !

 

Could be a problem with the airflow diverting system. I've encountered that before in a couple vehicles, the last one was a situation where setting the airflow to the floor setting only blew cold air, but if I moved the lever half-way between the floor/main vent setting and the defrost setting, the air switched down to the floor and I had full flow and heat. Unfortunately, too much was involved in removing the dash components to fix the problem and I decided to live with it.

 

Had a similar problem on my 02 HL. It is the 3 wire connector on the back of the temp control. The nut that holds the temp control to the dash loosens just enough so everytime you turn the temp knob or go over bumpy roads it makes and breaks the connection I found the fix on this site. A new control unit would cost approx 600 bucks. I repaired mine with a screwdriver, pliers, sockets and soldering iron in about 1 hour. Look back in this site and there is a real good post on this. Basically you pull trim off knobs from heater control and remove surrounding trim. Remove heater control and bring inside. Gain access to the back and you will see a flat wire with 3 strands in it. Resolder any loose wire. My end 2 wires were loose. Apply locktite to nut of header control so it won't loosen again. Reinstall in car. I will look at back issues in this forum and notify you if I wind the one that hepled me. Good luk.

 

Found the link I told you about. The question about heater control was asked by Toyteam on 2-7-2008. A reply under that question sent me to the web site www.Tundrasolutions.com/forum/highlander/3 2217-heater-quit-sort-of. Let us know if this helped.

 

Thanks airmech1953. I found that the other day too since I also belong to TS. I too figured it was the 3 wire ribbon. I plan to get to it eventually and see if that's really the problem.

Edit: Ribbon wire repaired and it fixed the problem. Link: http://www.tundrasolutions.com/forums/highlander/14033-heater-quit-sort-of/

 

I had the same issue with my 02, The temp knob may not be that loose but dont stop there if its not. My knob didnt seem loose until I removed the control unit and I could turn the nut with my fingers. It had broken the solder on one of the wires on the 3 wire ribbon cable. Which cause the cool to hot issue. Be careful when you solder the wire it took a few tries "limited space" but it will fix the issue. I was quoted 800-850 dollars to replace the unit which is the only way to get a new temp knob. I thank this forum for showing me the way to fix it myself.... Toytota should have issued a recall on this years ago but I guess selling new 650 units was just too tempting rather than doing the right thing.

 

Just to update...finally took the time to confirm it was the ribbon wire. One wire was almost broken through (and yes, the nuts on the two knobs were very loose). One of the 3 wires was broken but still making contact when moving the temp control knob. Plan to fix it this weekend. Only difficulty is finding small enough wire...

EDIT: Found small enough wire at a hobby shop. Learned to solder properly via the internet, bought the necessary supplies to suck up the old solder, and did it successfully. Haven't had a problem since (even through a major side impact accident).

 

Hi. Brand new here. Same problem on my 03 Highlander. Air temp switch is inconsistent. The nut under the knob was very loose. I tightened it and it did not solve the problem.
Looks like it is a loose wire problem as several have discussed here. My skill level with mechanical things is only average, and I am not confident about removing trim off of the surrounding area to get to the switch.
Is it easier than it looks ?

I may go to a local body shop I trust and have them remove the trim to get to the switch.
Very much appreciate the site and advice. Looks like I may save $1000 on this deal.

 

Also a good idea to add a lock washer underneath the control knob hold down nut. Otherwise it will keep loosening up even after the wiring fix...

 

You guys are brilliant. Thanks.

I had the intermittent '05 Highlander heater temperature control knob failure problem, too. I removed the control unit and found the broken 3-wire ribbon wire like you-all described. If it wasn't for your excellent descriptions, I never would have found it. Even though the knob was not "loose," apparently there's enough flex in the control mounting to allow this failure to occur anyway. I re-soldered and spliced in new wires and, voila, I get heat again when I want it...not just when the Highlander wants to give it to me. YAY. Thanks again. PS: I have written to Toyota Customer Service about this, like as if that will do any good.......

Update on my letter to Toyota about this: I got a call from a CS agent and I gave him an ear-full. Note that this was during the unintended acceleration debacle, so this guy probably was very busy trying to make a lot of Toyota owners feel less screwed. Anyway, he said he will pass along my comments (although he didn't say to whom...). I referred him to the TN website several times if he was really interested in seeing what we thought about this f'dup problem and the ridiculous, predatory Toyota "repair price estimate."

 

I think applying clear finger nail polish to the nut and threads will help hold the nut in place, too. Or LocTite threadlocker...

 

Thanks everyone!

Took 03 Highlander to local body shop. They removed trim over a/c control section. I took board out and took to a local TV repairman with copy of posts from this site, and he found the 3 ribbon wire and replaced the wires and resoldered them.
He asked for $20. I gave him $40!!

It works fine now.
I really appreciate the help on this site. Saved me hundreds here!!

 

Given that this was the heat knob issue again, I've added an entry in the DIY sticky that links to this thread. In the future when someone asks they can be referred to the sticky if you like. :thumbsup:

 

Awwwwwright!!!

Yay! Score one for us little guys. I wonder if the Feds will fine Toyota $16.5 million for this one, too, and give it all to us...:headbang:

 

I've got an 05 with a loose heat control knobm the loose knob is causing intermittant hot and cold air. I removed the control unit, opened it up. The back of the knob is directly attached to a small circuit board. The wires from the board are fine. I cannot access or see any nut to tighten the knob. It looks like the small board is snapped onto the knob and is one assembly, with metal clips on each side that holds the knob tight in the face panel.

I put everything together and reinstalled in the car. I didnt make it any worse but didn't fix it.

I've temporarily put a folded piece of paperboard into the groove around the knob, on the front of the panel to keep pressure on the knob toward the 10:00 area. It works, but looks goofy.

I will try installing sometning to pull the small board (and knob) tght when I have some time. I'll update this post with what I've tried, if successful.

If I missed something, and needed to dig further to fine the nut, I'd appreciate any help. I opened to control unit down to the control circuit boards, and could move the knob and it's small board around as one unit, didn't seem that they can be tighted relative to each other.

Although I didn't fix the problem I appreciate the info I found on this site, that gave me confidence to try and tackle it. Cost me 2 hours of time, and I'm not any worse thatn before.

 

The problem of the loose retainer nut is found under (behind) the black plastic knob which you actually grasp to adjust the heat. You must remove the plastic knob by pulling it straight out (it can be quite difficult to do because of a tight grip on the shaft). There is a metal hex nut under the knob, around the threaded shaft that projects towards you. That hex nut is a retainer nut that is supposed to hold the control in position, preventing the movement that eventually breaks the connector wires of the 3-wire ribbon.

 

thanks for all of the help. I tugged at the knob, and it pulled off. I was able to tighted the nut and the controller works again. I appreciate all of the posts and information.

 

SPOT ON guys!!! Same here pulled the knob and the screw was just about off. Hopefully caught it before any wire damage. Thank you for all your help!!:thumbsup:

 

Just joined to look for something else and came across this gem of a thread. You guys rock, and just fixed my cold/hot issues.

On a side note, the knob to the right that controls where the air blows feels loose as well. I can't seem to pull it off to try and tighten it, and I don't want to force it if it doesn't come off the same way. Can anyone verify it has the same type of removal process as the temp knob?

 

Just joined to look for something else and came across this gem of a thread. You guys rock, and just fixed my cold/hot issues.

On a side note, the knob to the right that controls where the air blows feels loose as well. I can't seem to pull it off to try and tighten it, and I don't want to force it if it doesn't come off the same way. Can anyone verify it has the same type of removal process as the temp knob?

Yes is pulls off the same way. Mine is having the same issue with the Fan Speed Control Knob not working. Going to see if I can fix it myself as well

 

link for a/c problem

Here is a link with some very good photos on how to repair the ribbon wire. If this is already in this thread I appologize. If not it's a very good diy.
http://www.devalcourt.com/2010/03/fixing-2004-toyota-highlander-ac-and-heat-issue/

 

Prevention action

So this post is for those who notice that their A/C knob is loose, but it hasn't gotten to the point where it has torn through or twisted enough to break one or more of the solder joints on the ribbon cable. This applies for sure on a 2001 HL - not sure how different it will be as the model years go up. I just noticed today sitting in the passenger seat that the left hand dial had *way* more play than the right. "that can't be good" I thought, remembering reading something BAD happens if you don't fix that. Found this thread. Got right on it as you can imagine.. Please excuse the dusty interior - need to clean..

Step 1: Grasp the loose knob and PULL straight towards you. It will come off, it is not held in place with anything more than friction:

The offending part is that 6-sided Hex washer nut that is supposed to keep the potentiometer / rheostat tightly in place. When the nut comes loose, it allows too much play, and the ribbon cable that connects this control to the A/C motherboard breaks or has intermittent failure. You can see the hex nut in this pic:

I always wondered what I'd use an 11 mm socket for. now I know! Just use the socket alone (without ratchet) to hand-tighten the hex nut tight. Then, using ratchet, just a tad more (like 1/16th of a turn) Remember, you are tightening down onto plastic (old plastic in my case) so you don't want to snap/bust it. And we're going to lock tight it in the next step anyway

It's my favourite colour - <ahem> ANYWAY using nail lacquer, apply a drop to the hex washer & metal stem. DON'T apply it to the black stem that comes out farther, or you will glue your control locked in one position :lol:. It will dry, basically doing the same thing as Loc-Tite or any other liquid lock product. i.e. this nut isn't going to loosen on it's own again.

Once your lacquer is dry, Re-apply heater knob by aligning notch in knob with notch in stem & push on. Bob's yer Uncle!

So to clarify, this is a Preventative maintenance step - this is meant for people who catch the control getting loose BEFORE it has snapped any internal wiring. Easy to do, < 5 min.
Dealer wants > $700.00 for new A/C board - their idea of a "fix", BTW.

cheers

D

 

loose nut also

Got a used 05 Highlander showing the same problem. Pulled the temp. knob off, tightened up the nut. Problem solved. (I hope) Thanks guys. Saved a pile of money with this quick fix.
Ya'll are the greatest.
:clap:

 

Same Problem

I have an '05 Highlander. I have this same problem, had new wires soldered in but now I only have heat. I am now looking to replace the entire unit. I'm wondering if my original part 84010-48091, can this be replaced with part 84010-48270. I found one for a reasonable price however it is slightly different. What I can see in the pic's is that the 48270 says max A/C on it.

Thank you in advance for any help.