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Very easy repair Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Mon, 4 Nov 2002 08:42:53
In Reply to: Continuity and voltage ... Why no seat heat?, jwr, Sun, 3 Nov 2002 12:41:49 Members do not see ads below this line. - Help Keep This Site Online - Signup |
First off, clicking is normal. Saab calls it a rheostat, but technically, it isn't. The device in the dash is a controller - there is some circuitry controlling a relay. The relay turns on and off, and that's what controls the heat. That click you hear is the relay opening and closing.
It should give a click every once in a while (many seconds apart). If it clicks very frequently (a few times a second) see below-
The relay contacts can get pitted and carboned up. This increases the resistance of the contacts. The seat pulls a lot of current, and a lot of current through that resistance means a voltage drop. So you measure no voltage. When you disconnect the seat and hook up your high-impedance meter, there is practially no current through the contacts, so no voltage drop - everything looks fine.
Here's the order to check things-
Make sure the seat heater element is OK. It may have broken again. Check the continuity of the element.
Make sure the ground wire from the heating element to chassis is good. (Black wire). If that's bad, no current will flow. Also, the temperature sensor in the seat uses that ground, and if the ground is poor, it'll affect the sensor.
If you think it's the controller, remove it from the dash and open it up. Clean the relay contacts with a little fine sandpaper. It won't take a lot- you're not trying to remove the finish, just the black carbon buildup. While you're at it, if it clicks a lot, clean the little contacts at the front of the switch, the rotary part. If that little rotary switch wiper makes poor contact, you'll get lots of clicking.
Not hard at all. See Quasi's site for info on opening up the switch (look under replacing bulbs)
Good luck.
posted by 192.249....
, Mon, 4 Nov 2002 08:42:53 <-- Viewing This Message, Mon, 4 Nov 2002 15:44:57
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