[Biturbos4] After-run thermoswitch modification

Ti Kan ti at amb.org
Thu Nov 15 23:19:31 PST 2007

Hi all,

I replaced my S4's after-run system thermoswitch today with a lower
temp unit as described in this Audiworld article:

The original switch (357 919 369F) operates at 112 deg.C whereas
the replacement (021 919 369) closes at 93 deg.C and opens at
88 deg.C.  Installation is basically as described in the article,
except that the electrical connector retaining wire does not need
to be removed.  You just squeeze it inward and the connector should
pull right out.  The old switch was stubborn to come out, and the
tight confines around it makes it difficult to get a good grip with
pliers.  But I used a vice grip and it worked like a charm.

After a long drive back from a dinner appointment, I pulled
in the garage and shut off the engine.  Lo and behold, the
after-run system activated.  The auxiliary radiator fan
and the reverse coolant pump were whirring, which I had never
heard before in the 8 years that I'd owned this car.  It ran
for approximately the full 10 minutes before shutting off.

I think this is a worthy modification, and should help extend
the longevity of the turbos.  Not only does it circulate coolant
through the system (including the turbos), the fan also forces
some airflow through the engine bay to reduce heat-soak.

Just thought I'd share.


More information about the Biturbos4 mailing list