[Aggman]

I did this repair sucessfully a few months ago, on the 2004 Highlander fan and temperature controls (automatic version). I found the following to be useful:

1- Test for continuity between each of the 3 conductors in each of the ribbon cables (both the fan speed and the temperature controls have similar ribbon cables prone to the same failure). I used an inexpensive VOM (Volt-Ohm Meter) to do this. The corresponding solder points on the control and mainboard are easy to access. There seemed to be some nonconducting layer of the solder (perhaps flux or an oxide layer) so scrape it a little to get a true reading. In my case only one of the outer filament wires on each control's flat cable read open.

2- Solder a jumper wire between the two corresponding solder points that are open; leave the flat cable in place. It does not matter if the broken filament reconnects with the solder at the control solder point. It is simply in parallel with the jumper wire and does not change the circuit. A needle nose plier is helpful to hold the short jumper wire while soldering.

This avoids unecessary work replacing the 3 filaments of each ribbon cable,
which is left in place and saves you from disassembling the control and motherboard to get at the ribbon cable.


The needle nose plier also turned out to be useful for tightening the small nut that keeps the control from rotating during use and opening the flat cable's circuit. This is worth doing even if there is no problem yet with your control, since it seems inevitable that without a locknut, the control will loosen with usage and torque the flat cable's outermost filament off of the control.

This forum was very helpful in solving this problem. The pictures by Toodle posted in message #233 and #234 were quite useful. The dealer wanted $1100 to repair this problem and $69 just to look at it initially.