Well this 2003 Toyota Highlander with the a/c stuck on heat finally made it back in so that I could find out what is wrong inside the a/c control assembly. I am planning on fixing, hopefully some weak solder connections. The temperature control switch had been loose and I tightened that up and the system went back to work for about a day before it failed again. I have found that even though the switch is now tight in the assembly, if I rock the knob up or down slightly rather than rotate it the blend air door will shift back to cool. The simple diagnosis is, if there is no control over the temperature control, remove the knob (pulls off) and check to see if the retaining nut is loose. Tightening the nut should restore operation temporarily and confirm that there is a broken wire inside the assembly.
To remove the assembly I first started at the lower edge of the trim panel and started pulling it out from the dash and worked my way around to the top side of the panel.
With the trim panel removed there are six, 10 mm headed blots that have to be removed. Be careful not to drop any. I dropped one and it took me about half an hour to find it.
Next I tilted the assembly away from the dash and removed two screws from both sides. I then had to pry the bracket away from the control assembly in order to clear the alignment pins.
Of course I had to unplug the wiring but it was too tight to get a picture of this but you can see the three connectors that I had to remove. I did not disturb the radio wiring because of the possibility of loosing stored memory and anti theft issues.
With the control panel removed, I lifted the clear panel away so that I could unplug the ribbon wire cable.
There is a plastic retainer that looks like part of the socket. It needs to be gently lifted to release the locking mechanism. I used a pick with a 90 degree bend to lift each end about an 1/8″. If this clip is not properly released, it will either break or shoot out and possibly be lost. Either way the job is over and you will have to buy another control head assembly, so be very careful.
Then the cable pulls straight out.
I then removed the screws that held on the rear cover.
Once the cover was removed I continued removing the screws that held the circuit boards in place and removed the nuts that held the switches in place.
With the circuit boards and switches removed from the assembly I could now see the real problem. Two of the three wires that connect to the switch circuit board were broken.
I clipped the last wire as close as I could to the circuit board. Once removed, I heated the broken ends of left over wire in the switch and pulled the pieces out with very small pliers. I then ran a piece of very small steel wire through the holes to clear the remaining solder. I used a razor blade to remove some insulation from the wire lead, fed the wires through the holes and soldered in place.
In hind sight I think on the next one that I will assemble the board and switches back into the control assembly and then solder the wires.
There was a little tension on the wire lead, that I did not care for, as I assembled the unit back together, so I heated up the leads a little and let the wires slide back far enough to take the tension off of the wires and the circuit boards.
I installed the control assembly back into the dash.
Then finished by testing and installing the trim panel.
The soldering and repair work internal to the control assembly was quite tedious and if you are not used to doing this kind of work, I would recommend taking it to some one that is. At least you will know what is wrong and you will not need to buy a control assembly that costs right at $700. For more information on the system please click here for part one.
I have added a few pictures and more detailed description in the above article. I am also updating the technique used to repair the solder joints.
There is not much excess ribbon cable and hardly any of us have that just laying around, so I use a razor blade to remove some of the insulation.
Exposing about 3/16″ of wire. I preclean the solder and old wire from the switches circuit board. Install the switch in the control assembly. I then guide the wires through the cleared holes on the exposed side of the switch circuit board. I gently mount the main circuit board back into the control assembly, pull the ribbon cable back slightly and solder the wires into place.
I find this much easier than trying to work the ribbon cable through from the original direction.
If I understand you correctly, your mechanic cleaned the air flow passages of the condenser and radiator. Then replaced some missing/damaged foam around the side edges of the condenser. That would be a good diagnosis and repair of an unusually high discharge pressure. Assuming it continues to cool well, you should be okay. I personally prefer to blow air through from the engine side to remove most of the debris and then follow up with soap and water, if I feel it is needed. I also look between the condenser and the radiator for large pieces or accumulations of debris.
Great response, however, today I decided to take the car to my mechanic shop and after he ran his diagnostic, he started to put some water and wash the a/c condenser. Interesting enough the ac started to blow cold air. Basically he was telling me that when the ac fan starts running, since there were lots of gaps between the radiator and the condenser he covered that gap with a foam. Now, even though tha the ac is blowing air right now, I’m worried that this might be temporary. Would you think that I should change the condenser and the dryer (just to be on the safe side).
I look forward to your expert advise.
Regards,
Andy
The compressor turning on is not enough to determine if the refrigerant charge is proper or not. The only true way to tell is to recover and measure the refrigerant with the proper machine. In lieu of that I would recommend checking the a/c lines at the fire wall area if they are accessible. With the engine running and the compressor on for at least five to ten minutes (doors and windows closed, a/c set to maximum cooling and fresh air door closed) , check the temperature of the lines. One should be warm and the other cold. If they are you have a door control problem. If they are not you have a refrigerant type issue. Use caution around moving and hot surfaces. If you have access to a/c gauges, pressure readings along with ambient temperature and humidity would be very helpful.
Dear Sparky, I’ve 2003 Toyota HL and after taking it to the dealer their diagnostic’s conclusion was to replace the a/c control panel. So I took the car back and decided to order the part myself ($680) and installed it, but unfortunately the a/c is still not fixed and it just blows air (not cold at all). The compressor works because you can hear it and the A/C light does not flickers. Also, the dealer was not able to find any any problems/leakage or a need to add more freon to it.
Id there anything that I’m missing or should be checking (e.g fuse or ….)?
I’m desperately seeking your advise.
Thanks a much!
Andy
Hi Jeff,
As far as I know, it does not.