Re: after-run fan switch (more)

[Aleksander Mierzwa <alex@matrix.com.pl>]

At 12:15 17.06.98 -0500, Daniel R. LeFebvre wrote:

>problem:  i suspected that there was a malfunction with my after-run fan
>when i had to keep occasionally jumping my car.  (i just installed a new
>alternator last week, it was smoked).  the fan, when it would come on
>(will on fun when the engine is truly warm, not just everytime i shut
>the car off), would run for the full 15 minutes (i am correct in
>thinking that there is a safety mechanism that shuts the fan off at this
>point in time?).

Yes, there's a time limit for the after-run fan. In case of my 5KT it is
about 20 minutes.
Once the fan kicks in, it usually does run pretty long. The point here is,
the afterrun fan should run only when the car is truly hot (the switch
closes at 110C and opens at 97C). To reach that temperature the car has to
be driven for a while, usually enough to charge the battery. It is possible
that on your car either:
1) The battery is weak and can't handle the normal operation of the fan
2) The switch is faulty or wrong (it is often confused with other switches,
carrying similar p/n but operating on different temp - BTDT)
3) There's a short in the wiring between the switch and the relay or the
relay is faulty
4) The electric coolant pump doesn't run, hence it takes forever for the
fan to cool the engine.
5) The resistor pack is faulty, causing the fan to run at full speed (over
40A!) and drain the battery.

>i was emailed by someone with a similar problem, and
>told that the problem was a thermoswitch located at the bottom of the
>radiator.  

Nope. The switch in the radiator is responsible only for operating the fan
with the engine running. Once the ignition is switched off, it does not
have any effect. 

>so i went to order this part, and the guy told me that he
>needed some color codes.  well, i couldn't find the switch, so i brought
>it in for him to look at.  he went to a switch which inserts into the
>head of the engine block, towards the back ,at a point where a radiator
>hose also inserts.  he said this was the switch, and if the fan was
>running in after run mode and i pulled the wire, the fan should stop.
>so i did this and the fan did not stop.  i suspect either 1)this is not
>the after run switch (when i was hooking it back up i thought i heard a
>few quick bursts from the injector cooling fan, could have been
>coincidental), or that i have another probelm.  help please.  tia

The after-run fan thermoswitch is located at the back of the upper coolant
hose housing. It has two spade connectors. Disconnect them from the switch
and the fan should stop running. If it doesn't, there's a problem with the
wiring or relay. Beware, one of the connecors has voltage on it, do not
touch it to ground! The correct replacement switch is p/n 054 919 369B,
white insulator with red dot, about $15 from the dealer.

Aleksander Mierzwa
Warsaw, Poland
mailto:alex@matrix.com.pl
87 Audi 5000CS turbo (mine)
88 Renault Medallion wagon (mom's)
91 mountain bike (just in case both cars broke at the same time :-)