FotoVeloce

I searched archives. Plenty on seat heaters that don't work. My problem is that the passenger heaters works too well! Eveyrone that rides in the car has to turn the heater off. For some reason it seems to come on HIGH every time I re-start the car. This is a big pain in the butt for my passengers.

Today, I had a backpack riding in the passenger seat and it was enough weight to turn on the heater. I could smell it. It was very hot to the touch too. Reached over and hit the 'off' switch, again, and it cooled down.

What could cause it to always be on? Switch I guess but no clue how to diag the switch for problems. Maybe it's just not being used properly (howeve I have no issues figuring out how to use the heat in my driver seat, and I have to turn it on every time I start out... passenger seat is always on).

Maybe the switch is shorted out or? Well.. I'm looking for suggestions.

JasonAndreas

1. Remove switch cover (4 screws).
2. Disengage seat heating switch and pull out switch (take car not to damage the wire).
3. Switch on ignition.
4. Connect voltmeter to term. 1 (positive) and term. 2 (negative).
Display: Approx. 5v

Note
If no voltage is displayed, check power supply according to wiring diagram.

5. Connect voltmeter to term. 2 (negative) and term. 3 (positive).
Display, depending on potentiometer setting: approx 2 - 3V

6. Push tip switch into "on" position and keep it in this position.
Display: approx. 5V

7. Push tip switch into "off" psition and keep it in this position.
Display: approx. 0V

8. Turn knurled wheel of potentiometer all the way up.
Display: approx. 3V

9. Turn knurled wheel of potentiometer all the way down.
Display: approx. 2V

10. Remove seat and connect to Special Tool 9269.

11. Switch on seat heating and set to maximum heating output.

12. Measure voltage at 2-pin connector marked with digit 3.

When the seat heating is switched on, the voltage oscillates between 0V and approx. 12V (clocked voltage).


Checking resistance of heater elements

Note

Use a digital ohmmeter for the measurements.

1. Disconnect connector marked with digit 3.

2. Zero out ohmmeter.

3. Connect ohmmeter on pin side.
Display at 20C ambient temperature:
1.5 to 1.8Ohms.



There is also a way to calibrate the control unit and the heating element but I'm not typing that in. If someone buys a new control unit or heating element I can send them the page(s) from the workshop manuals.

DougB

I had this same issue some years back. In my case the problem turned out to be the potentiometer on the switch. I was able to fix it somehow--perhaps by tweaking the wiper portion of the potentiometer. Sorry I don't recall the details but I do remember that it wasn't terribly difficult.

-doug

FotoVeloce

Wow. Thanks for the detailed info! I really do love this place!

I've tried to fix the sunroof switch in my '95 (taken it all the way apart) so disassembly of the switch should be simple work. I have a nice Fluke meter so.. looks like I have the tools I need as well. Ah.. something to do with the kids this weekend! They love helping daddy work on the 'Super Fast Cars' (I crack up every time my 4 year old says that...)