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Seat heaters . . . do the elements go bad?? Sticky element connections . . . 700 1990

posted by  gmcpheeters on  Thu Nov 29 05:48 CST 2007
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last visit: Sat Apr 19 00:15 CST 2014
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I've got my seats torn apart to replace the lumbar support and figured I'd a little energy trying to fix the seat heaters.

I confirmed the right signals coming through the wiring harness to the relays. Bench testing the relays, I found that they come on for a few seconds and then turn off. I sort of figured it would be all or nothing, but I'll take that as a clear signal that the relays are in fact broken and I need to replace them.

That leaves one question - there is some sticky gooey substance coming down from the wires in the passenger side lumbar heating pad. Should I be worried about this? I have no idea what it could be . . . but appears to be coming from the wire leads, maybe the wire insulation breaking down. The seat cushion element also shows some signs of staining, but doesn't have the stickiness of the lumbar pad.

To test these elements, can I just hook them up to a 12 volt battery and see if they get warm?

thanks. Pic attached -









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    Seat heaters . . . do the elements go bad?? Sticky element connections . . . 700 1990

    posted by  Herb Goltz on  Thu Nov 29 06:37 CST 2007
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    The seat heater relays are thermostatically controlled, so if the temp is above some amount, they will shut off (I think the exact amount is in the 700/900FAQ, if memory serves it is somewhere around 10C). That said, resoldering the relays or swapping them with a good one is worth a shot-- I have had one fail because of cold solder joints.

    I think there is also information in there about how to test continuity-- the circuits are more complicated than on the 240, where invariably it is the thermostat or it's connection that fails.

    I also seem to recall that the switches are more complicated, and that the switch bulb is actually in the circuit for the heater, so if the bulb is out the switch won't work, but it has been a while since I looked at one and it might be wrong.

    See this post by Dave Stevens, who has written more on the topic, if memory serves...

    http://www.brickboard.com/RWD/index.htm?id=1007288

    Good luck!

    --
    Herb Goltz, Aurora, Ontario, Canada '92 945t 210K mi







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