[Fixit]

Thanks for this solution and the images as well. I'm seeing in a lot of posts about this problem and it appears that a great deal of these vehicles are driven by women as is the case with mine. What are the two most important things women want in a car? 1) Reliability (The reason we bought a Toyota!) and 2) HEAT!! (The one thing never dies in any car!) So why is such a fundamental function going south in the supposedly reliable Toyota? I asked the parts people and dealership managers and no one knows. They just play dumb and shrug their shoulders, as usual. Unfortunately this won't be recalled because it isn't a safety issue so they suggest calling the Toyota customer service group which I will do and I encourage everyone else with this ridiculous problem to do the same. Apparently they made good on a problem with the run flat tires on the Sienna vans that caused them to get like 10 mpg. It's great that everyone is getting together to help each other on this but at $1000.00 to fix a defective factory part Toyota needs to address this. I’ve owned a dozen Toyotas in the last 25 years and never had such a stupid problem with one! Maybe they should go back to cables and vacuum lines!!!

Originally Posted by dfluitt

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.