Re:computer controlled thermostat

[Jim Cash <j.cash@xxxxxxxxxxxx>]

Randy writes:

> The electric auxiliary fan (on front of radiator) is "infinitely variable", so it keeps the
> temp right where it needs to be for the computer's "needs".

If that is so it is a new design that I have not seen.  The technical
info that I saw for the E39 & E38 show the standard 2 stage operation of
the aux fan (low speed and high speed - no infinitely variable.)

The low speed fan starts when the coolant "in the rad" exceeds 91C (or
the A/C is switched on).
The high speed kicks in if the coolant "in the rad" exceeds 99C. 


But they want the coolant in the engine to stay warmer than that
(between 108 & 112C)- therefore the computer control.
Actually the "Computer Controlled Thermostat" is just that - the
computer operates a small electric heater in the coolant chamber next to
the thermostat, which helps the thermostat respond more quickly in order
to keep the temperature tightly within the optimum range.  I do not have
the specific reference for this functionality but I remember reading
this in some BMW writup.


Cheers

Jim Cash

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