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2003 Toyota Highlander Temperature Control
Posted to Technical Tips Forum on 5/4/2012 14 Replies

Customer showed up with the complaint of not being able to set the temperature in her 2003 Toyota Highlander. Testing found a faulty climate control module (manual air/heat control unit). This is not a cheap part and the customers always question the cost.

I have seen this several times myself as well as a few times on the help requests. The replies on the help requests state to tighten the nuts up that are behind the temperature and air flow position control knobs. While this will help with the symptoms it is not the true fix.

The problem is caused by the loose nuts behind the knobs since this allows the control variable resistor to move around and break either the solder joint or wire(s).

If you are comfortable soldering small wires then the repair is relatively simple. Remove the climate control unit and separate it from the brackets that hold it to the radio.

Remove the eight screws that hold the back of the control unit in place and pull the back off. Disconnect the flat wire strip that connects the two circuit boards (there is no plastic connector on the end of the flat wire strip, it just pulls out).

Here is the back side of the temperature control knob and the two retainers that hold it in place. Remove the nut and washer from the front side of the control unit (under the knob). Using your finger, push on the front side of the temperature control while pushing one then the other retainer off to the side with another finger (no screwdrivers needed).

Now you have access to the circuit board for the temperature control. Carefully inspect it for broken solder joints and/or broken wires. As you can see, this one had a broken wire as well as broken solder joints. If you are lucky and just have broken solder joints just carefully reheat them with a tiny drop of fresh solder, reassemble, install and you are done.

With a broken wire you must remove the other wires from the circuit board using either a solder removal tool or a solder wick. Once the wires are removed, carefully strip them back. There is just enough extra wire to perform this repair once.

Now carefully prepare the solder pads on the circuit board by removing any excess solder. Make sure the holes are open and clean, otherwise you will have a difficult time getting the wires back in.

Insert the wires and solder them in place. Make sure to inspect the solder joints on the position control as well although I have only seen one that needed work there and that was just a broken solder joint. Install the temperature control circuit board, reassemble and install the control unit.

I have found that if the wires are broken it is easier to remove them from the larger circuit board and install a new set of wires. I solder them to the small circuit board first since it is easier to position it when the other end of the wires aren't connected to the larger circuit board. I purchased a roll of flat four wire at Radio Shack that works perfect. It is the same size as the original wires. I just cut a piece to length, pull off the extra wire, strip the ends and solder away.

One tip for working with screws in plastic. I hate finding broken or stripped threads in a plastic part. Each time a screw is screwed in place it cuts new threads, do that enough time and the hole strips out. I find that turning the screw backwards until I hear it click and feel it drop into the hold slightly gets the threads in the hole lined up with the threads of the screw.

Total time for a standard solder only job is less than 30 minutes (R&R included). If you have to replace the wire then I find it takes about 20-30 minutes more. Don't forget to charge twice your labor rate since you have no income from parts on this job.

I have done several Toyota Highlanders and would guess (but can't say for sure) that the other climate control units in the Camry and Corolla would be similar and may suffer from the same problem.

Eric from Wisconsin

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car Vehicle Data

2003 Toyota Highlander 2.4L

Engine2.4 L
Trans4-speed Automatic (Electronic)