This 2003 Toyota Highlander came in with the complaint that the a/c only puts out hot air. I confirmed the complaint and removed the glove box to access the air mix actuator assembly.
I had to push the hinge pins out to remove the glove box.
I then had to remove the screw and bracket that hold the cable.
With the glove box out of the way, I had to remove one screw and release some retaining clips in order to remove the white duct assembly.
I checked the feed back sensor (orange wire) and it was reading about .8 volts at the full heat position. I started moving the temperature knob while watching the voltage and I noticed that the actuator arm would occasionally move and the sensor value would change. I found a sweet spot and the actuator would move to almost full cold. Looks like I need to go to the control assembly.
I first wanted to check the switch and knob to make sure nothing was stripped and after pulling the knob off I found that the switch was loose in the control assembly. I tightened the nut and the system now works properly.
I would assume that the actual switch mount is one of the control circuits and it could not make proper contact with the nut loose. Well, this turns out to only be a diagnostic aid. I will have to go deeper into the control head as soon as the customer can leave the vehicle again. I checked on the price of a new a/c control assembly. Almost $700 from the dealer and the only service part is the blower switch. This one is okay.
I have fixed this one and I will be giving an updated post in a few days. Pretty delicate work but it saved a $700 control assembly. Click here for updated repair.
The ribbon cable slides into the slot and the white locking bar is pushed down to lock the cable in place.