SJ Audi 100 Won't Start (Vacuum Leak?)
audi at humanspeakers.com
Mon Feb 2 23:14:54 EST 2004
> I unplugged the lead to the potentiometer during cranking.
> One thing that was curious was I had read to 'ensure the potentiometer is
> properly grounded'. Does it get its ground from the 3 pronged plug?
Yes, as its name implies, it's just a potentiometer - ground on one
side, 5v on the other, and an output varying with plate position riding
in the middle.
> It was also curious why the resistance actually dropped towards the end of
> its deflection. This doesn't seem unique to mine. Someone else in the
> archives had done the same test and got a similar result. I'd bet its a
> valid engineering design (eg for full deflection you'd need to be
> decelerating...although i know this is also handled by the DPR) ...but it
> could also be a worn potentiometer?
Could be, yes. I'm not impressed by that drop at the end, though it
probably isn't affecting your problem. Nate and I rigged up a harness
once and played with a few, key on, and measured the voltage. The 2 or
3 good cars smoothly rose over the plate range. A bad one had some
dropouts in the middle (wiper losing contact). So we broke it open to
At full deflection you'd be getting maximum airflow - why would you need
to be decelerating?
Too bad these aren't replaceable - I think they should be.
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