Originally Posted by Robo
If you look at Roadrunners post:
This is a repair of the Thermistor connection, not the heating element. There is no part number or printed characteristics on the thermistor themselves. It would appear to be a small wire covered in plastic with a black wire on each end, then covered in plastic and embedded in the leather cover. There are three thermistors wired in series on the bottom cover, (not on the cushion) The wires pass thru the foam and end up at the six wire connector as the two gray wires. two of mine are open. All of my heating elements are fine. Only the temperature sensing portion of the circuit has failed. Seems like throwing the baby out with the bathwater to overlay heating pad that are fine. Just wondering if anyone has replaced the thermistors and is aware of the proper characteristics.
Thermistors come in many shapes & sizes, but basically all work the same.
They are rated by their resistance value at room temp. This value then changes as the temperature does. See example on Digikey.com - part no. 490-2446-2-ND scroll down to read their "Data Sheet".
NOTE: this is NOT the right part for your seat; only an example of what a thermistor does.
So if all 3 are wired in Series, we should be able to measure what the resistance is between the 2 grey wires on the seat; seat unplugged from vehicle (working heater at Room Temp); Divide this by 3 and we have the value. Next plug the seat back in & turn on the heater for a minute or two; quickly disconnect and recheck resistance (before it cools) between same two grey wires. It should be different. It will tell us whether the resistance goes up with temperature or down. All that is left is to identify the package type of the thermistor.
Anybody have a working seat heater & Ohm Meter?