Repair/replace heated seats/Redux

[Coof]

The driver side seat heater of my 2000 Buick Park Avenue is not working. I tried several diagnosis steps but have not yet figured it out. The passenger side works great, so I have been comparing left and right sides.
Here is what I know:
The indicator light of the switches for high and low settings work on both sides. The resistance of the heater elements are the same on both sides. The two bottom elements in each seat are 1.2 ohms and the lumbar element is 2.2 ohms. The voltage at the 2x2 connector coming from the seat heater controller is 10V across two of the adjacent pins and 5V accross two of the diagional pins. One pin has 0 Volts. This is the same on driver side and passenger side. I bought a used seat heater controller at a salvage jard. The results are the same, no heat on the drivers side.
If the heater element is burned out, I would expect to see an open circuit or shorted circuit. Based on the resistances, I concluded the heater elements are okay. I pulled partially pulled the leather up and inspected the bottom side of the seat element. I did not notice any burned spots or anything else unusual.
I think the problem is common, because I have seen seat heater problems for the driver side posted at various web sites. Does anybody have any ideas how to diagnose the problem? My next step is to plug in the driver side controller on the passenger side. I cannot get the passenger side controller out because the front trim won't come off without damaging.
Thank you, Rob

[Tech II]

The usual problems are the elements or the seat module......if the elements are not open, switch the modules...believe they are the same part number...

[HotZ28]

Coof, we started a new thread for you, to help eliminate the confusion created by reading so many post from a 4-yr old thread, before we get to the question. Please feel free to open a New Post with current issues. You may attach a link to the Old Thread if you wish. Thanks.

[Coof]

I found the problem. The heater elements are ok, switches ok, and heater control modules are okay. There was a defect in the thermistor circuit.
The output connector of the heater control module is a black 2*2 connector. The two heavier gage wires power the heater elements. The two thinner gage black and red wires are for the thermistor. The heater splits of into 3 heater serpentines in series sewn into the foam backing leather seat cover two of these connect with 2-pin green connectors. There are 4 wires in a black cable sleeve going to the back of the seat. The black/red wires are soldered to very thin gage blue insulated short wires which go to the thermistor. You have to tear some of the foam to get to it. The thermistor is a 2 or 3 mm small black disk. The thermistor is attached to the heater wire. One of the blue wires had come off. I was not able to re-solder it. Instead, it wired in a small 1200 ohm resistor. The heat works again. It is no longer thermostatically protected. I just have to turn it to low or off after it gets nice and toasty before it burns my cheeks. Good enough for now. Post a reply if anybody has questions. Purely coincidentally I was at the mfg plant today where these seat heaters were made.

[Tech II]

Good diagnosis!

Never ran into a thermistor problem, but I guess there is a first time for everything....