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Seat heater operation Posted by Ari [Email] ![]() ![]() In Reply to: Seat heaters RTM!, Brooks G, Mon, 28 Mar 2005 20:10:20 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The three-position seat heater has been pretty much the same since it was introduced in the 9000 in '86. There is a temperature sensor in the seat cushion (a negative temperature coefficient resistor, to be exact). It shares a ground with the seat heating element. The sensor wire and heating element wire go to the controller.
In the 0 (off) position, nothing happens. That's easy. The next three positions (1,2,3) positions on the controller correspond to seat heats.
If the switch is set to 1, and the seat is cooler than that temperature, a relay in the controller closes, and sends 12 volts to the seat heater element. Once the temperature of the sensor in the seat gets above the setting on the controller, the relay opens up. There is a little deadband (hysteresis) in there so the relay doesn't chatter. Once it cools off a few degrees, the relay closes again. The higher the setting on the switch, the hotter the sensor in the seat has to be to switch it off.
All ventilation does is add some airflow through.
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