Re: E34 Auxilary Fan not working!

[Jim Cash <j.cash@xxxxxxxxxxxx>]

Eugene Hoe writes:

> My auxilary fan on my E34 525i M20 doesn't seem to be working. Its a new fan and I recently changed the
> radiator temperature sensor as well which activates the fan. I did a manual by pass of the wires and the aux
> fan works fine. However when I plugged it to the sensor like normal, it doesn't come on when the engine gets
> hot which is what it is suppose to do!!.


Well - not really.

i am not sure what the temperature setting is for that low speed fan
switch on your E34 - but it is probably somewhere between 89 & 93 C
(probably closer to 94 - should be stamped on the side of the switch)

It brings on the low speed fan (by causiing the low speed fan relay to
operate and send voltage to the resister) when the temperature of the
"coolant" in the upper rad gets to that temperature.  I put a lamp in
the dash on my E28 to monitor when the low and high switches kicked in. 
I only saw the low temp kick in a few times in the 14 years I had it
(91C) - and I never saw the high one operate (99C).


The low speed fan does however normally cut in when you turn on the AC,
regardless of the collant temperature switch.


Soooo - if you know for sure that your coolant in the rad is over that
temperature then you have a problem. But since the system works when you
short the contacts of that switch then the only fault can be the switch
itself. You can test it by placing in a pot of water with a thermometer
and monitor the temp of the water while heating it past the temp of the
switch. Put a meter on the contacts to see if they operate at the
correct temp.

you shuld be able to remove that switch without much coolant leaking out
as long as you do not have any other open points in the system (keep the
cap on).

Hope that helps

Cheers

Jim Cash

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