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