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Probably not the thermostat Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Tue, 12 Nov 2002 08:34:04
In Reply to: seat heater thermostat, jwh, Mon, 11 Nov 2002 11:26:39 Members do not see ads below this line. - Help Keep This Site Online - Signup |
I'm not saying thermoswitches don't fail, but I've never seen it. It's almost always a break in the heating element, which is easily fixed.
Saab went to a different seat heater controller for the 900 in your time frame, and I'm no expert on exactly what was in which car. But I'm pretty sure the passenger seat had the old style - no switch or controller in the dashboard for the passenger seat.
Power comes to the seat all the time the ignition is on. It goes through a switch on the underside of the seat - look for a chain. This switch keeps the seat off if there is no occupant. It then goes into the seat, where there is a thermoSWITCH in series with the heater mat. The switch closes when the seat temperature drops below 50F, and shuts off when the seat goes over 82F.
Check for voltage with the ignition on. Make sure the switch works. With the ignition off, and the seat less than 50F (first thing on a cold morning?) measure resistance at the seat heater connections. This is from memory, but it's typically the yellow or yellow/white wire (high) and black (ground). You should see a few (2-4) ohms. Typically the heating element has broken, and you see an open circuit.
The most common place for the heating element to fail is at the front outside edge of the bottom seat cushion. It gets the most abuse. However, it can fail anywhere. It's easy to fix - find the break and resolder it. Yes, you can replace the heater mat, but I've never had to.
If you undo the bolts holding the seat down, flip it backwards. Undo the metal clips at the bottom that go up through the seat cushion. Peel back the seat cover. Typically it's easy to find the break, because there will be a little scorch mark in the foam where the wire breaks. Pull the wires together, solder them, and wrap with some electrical tape. I like using heat shrink tubing to cover the joint.
posted by 192.249....
, Tue, 12 Nov 2002 08:34:04 <-- Viewing This Message
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