After-run Sensor Test???

[Henry A Harper III]

It's my understanding that the 10vt cars trip the after-run more frequently
than 20vt cars (all else being equal) due to sensor location and perhaps
coolant path, but on my 20vt I have to turn off the ignition *while the rad
fan is running*, hood closed, ambient "warm" (80degF+ ) in order to get
after-run to kick on. If you wait until the fan has quit, the coolant is
too cool for the after-run :), on my car at least. It may take up to a
minute for afterrun to begin, according to Bentley. I have replaced my
afterrun sensor when it failed this test previously.

HTH
Henry Harper
http://www.henry-harper.com hah at alumni.rice.edu
1991 200 quattro, 118k
1988 GTI 16v, 236k

On Wednesday, May 21, 2003 6:12 PM, Darek Jarski
[SMTP:darek_jarski at hotmail.com] wrote:
> SJM site makes it sound like the afterrun system should kick on any time
the
> engine is turned off while at high enough temp to trigger the normal fan
> speed. However, it sounds like the threshhold is a little higher. Am I
> correct in assuming that since it turned on once the system is operating
> correctly? Seems like a reasonable conclusion; however, I was under the
> impression that the afterrun system is triggered more frequently ... am I
> mistaken on this point?
>
> Thanks for the help,
> Darek
> '89 200tq
>
>
> >From: Tony Lum <tlum at Gigatronics.com>
> >To: Darek Jarski <darek_jarski at hotmail.com>
> >Subject: RE: After-run Sensor Test???
> >Date: Wed, 21 May 2003 14:38:15 -0700
> >
> >
> >
> >-----Original Message-----
> >From: quattro-admin at audifans.com [mailto:quattro-admin at audifans.com]On
> >Behalf Of Darek Jarski
> >Sent: Wednesday, May 21, 2003 1:31 PM
> >To: quattro at audifans.com
> >Subject: After-run Sensor Test???
> >
> >
> >Quick question:
> >I was almost sure that my afterrun sensor was bad [since the system
never
> >turned on] so I have one the way from the dealer. Yesterday the pump and
> >fan
> >kicked on after a normal drive [for the first time as far as I know]. I
> >haven't been able to get it to kick on again. As a test, I let the car
warm
> >up to the point when the first stage fan kicks on then I turn it off and
> >wait ... nothing happens. [If I jumper the two wires the afterrun system
> >kicks on.] Hence the question: is there a sure way to find out if the
> >sensor
> >is bad [i.e., via a ohm meter, etc.]? Second, is possible for it to work
> >intermittingly?
> >
> >Thanks,
> >Darek
> >
> >_________________________________________________________________
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> >You could remove it and suspend it in water with an ohmmeter attached to
> >the
> >terminals.  Now with a thermometer in the "bath" raise the temp of the
bath
> >till the ohmmeter (or maybe a continuity buzzer) indicates a short.  I
> >think
> >the temp is rather high, I've only heard mine go off once or twice.
 Check
> >www.thepartsconnection.com to see if there's a lower temp unit that will
> >replace the OEM.  I did this to my fan injector cooler which now trips
at
> >85C vs. 90C and it runs the injector fan almost every time I shut the
> >engine
> >down.  Also make sure the after run pump is not seized.  If it is,
you'll
> >soon fry the 571A after run relay (burnt traces and blown transistor).
> >
> >HTH,
> >
> >Tony
> >'83 urq #DA900302
>
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