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Re: Feeble seat heat Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Mon, 7 Nov 2005 08:53:24
In Reply to: Feeble seat heat, J Schuh, Sun, 6 Nov 2005 21:30:00 Members do not see ads below this line. - Help Keep This Site Online - Signup |
I don't know the values exactly. The seat heater element should probably be on the order of 2-3 ohms. Most meters don't measure accurately at those values, so continuity or at least less than 10 ohms should be enough.
The system is not a thermostat and a rheostat - it just looks like one. There is a temperature sensor in the seat - it's a variable resistance with temperature. The resistance drops as the temperature increases. Depending on the temperature, it will be in the 1000 - 8000 ohm range, give or take. The device in the dash is not a rheostat (variable resistor). It's a little electronic circuit. The little wheel selects three resistance settings, and Off. The controller measures the resistance of the sensor in the seat, and if the seat is colder than the setting on the wheel, a relay in the controller closes, and puts 12 volts to the seat. The seat warms up, and once the temperature gets above the setting, the relay opens. When the seat cools down a little, the relay closes again. So the heating element sees either 12 volts or 0. The higher the setting, the longer the relay stays closed.
If the seat doesn't seem to be putting out heat as well, there are a few things to check. The seat and thermostat share a ground point under the seat. If the ground is bad, it can mess up both the temp reading, and how much current you can push through the heater. If the contacts on the relay are dirty, that poor connection will reduce heating effectiveness.
Push the seat all the way forward, and access the connector under the seat for the heater. Keep it connected to the seat. Put the ground point of your meter on a good chassis ground, and set the meter to volts. First, with a cold seat, turn the seat heater to 3, and measure the Voltage from the ground wires (Black) to chassis. The voltage should be less than 0.1 volts. If it's greater than that, follow the ground wires and fix the ground. Next, move the positive lead to the yellow wire, which is the power from the relay. It should be 12 volts, as the seat heats up. Actually, it should be within about 1/2 volt of the battery voltage, and since the car should be running, probably closer to 13. If you see 12 or 13 volts, that's a good sign; if you see less, like 2 or 3 or 5 volts, then the relay contacts in the controller need cleaning. If you see 0 volts, then the controller may be bad.
The controller has a little switch that wipes over the contacts inside, and if those contacts are dirty or screwed up, that could cause a problem.
If you think it's the controller, know that any controller from any year 900 with a controller, or any controller from ANY year 9000 will work. So if you find one used, go for it. There was a slight change in newer 9000's, but all that meant was that the bulb could be replaced without soldering. But pin-for-pin, identical.
posted by 192.249....
, Mon, 7 Nov 2005 08:53:24 <-- Viewing This Message
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