[s-cars] Mysterious Elec Problem - Temperature Warning Light always on

[Mike Bishoff]

Folks - The warning light on my '92 S4 comes on and starts blinking after
about 15 seconds. This happens whether the car is cold or not. I checked the
anti-freeze level and it's well within the acceptable range. I replaced the
multi-failure sensor on the engine knowing that was causing my gauge not to
work, but that didn't solve the warning light problem. I removed the
electrical coupling from the bottom of the anti-freeze tank thinking there
may be an issue with that particular sensor. I jumped the contacts as well
as kept the contacts open, each time starting the car and each time getting
the same warning light. I went as far as disconnecting the battery in case
some error code was hung up in the ECU. No luck.
 
I suspect the anti-freeze tank level circuit is the culprit, but don't know
how to proceed on diagnosing that other than what I've already done. Your
collective wisdoms appreciated.
 
Mike - Seattle, WA