[s-cars] seat heaters

[Wayne Dohnal]

>Checked voltage with me sitting in the seat, and have 13+ on both
>terminals 5 and 6. My bum is strangely getting a bit warm though not
>like I remembered.

If we're using the same numbering system, pins 5 and 6 is the brn/blu jumper 
wire between the seat and backrest.  If you're measuring +13 between there 
and ground (brown wire), that would indicate that the backrest element is 
out.

>What's wierd is that the volts seem to fluctuate from 13 to 6 and back
>again. WTF is up with that?

  ~6 volts is normal here because the seat and backrest elements are 
connected in series.  When it's 13, the backrest element is open.  When it's 
6, the backrest element is working.  This supports the theory of the element 
opening up when it gets warm.

But just because I sometimes get things backwards I'd feel better if you 
somehow confirm that it's the backrest element that's really the bad one. 
Perhaps you could apply pressure to the backrest while watching the 
resistance measurement and see it glitch when you push on the right spot. 
Then follow the wires to see if they go to the seat or backrest, or confirm 
with the wiring diagrams.

The seat controller does not act like a potentiometer.  It outputs either 
full voltage or nothing.  It's more like a furnace thermostat, either on or 
off.  The comnbination of the thumbwheel position and the temp sensor in the 
seat determine when the controller turns the elements on and off.

>Sometimes I just wish things would break!

Perhaps you'd like to trade cars?  Mine regularly makes this wish come true!

Wayne Dohnal
1994 S4