Fan runs with heat on

[Henry A Harper III]

On Thursday, January 09, 2003 4:30 PM, Navistrpwr at aol.com
[SMTP:Navistrpwr at aol.com] wrote:
> >What's the outside temperature when this happens, and are you in "econ"
> or "auto"?
>
> It was in the mid 30's outside when I was checking the system out.  The
fan
> runs in 1st speed at any outside temperature, however, with the heat on
in
> auto mode.  In econ mode, the fan doesn't run.

Then it is operating properly as designed. Econ means "don't run the a/c".
Any other "on" mode besides econ means "it's ok to run the a/c". That is
the way it works, lifted from 80's GM remember. If you don't want the fan
running when it's winter, use econ for the winter except once a month or so
to keep the compressor seals alive.


> >In Auto, the fan runs, because the ac clutch could become
> active.
>
> The ac clutch shouldn't come on in the 90 degree setting though, should
it?
> If that's true, then I don't see why the engine fan should run.  With the
fan
> constantly on, the engine doesn't get warm enough to produce good heat.
 I
> checked the heater valve, it's in the fully open position.  Also checked
the
> hoses going to and from the heater core, they were warm, so this rules
out
> the valve.  Just spent $120 at the dealer today for a new control head,
that
> didn't solve the problem either.  Running out of ideas and money...

In the "auto" position, the a/c clutch will be on as long as the temp in
the evaporator coils is above freezing, regardless of temp setpoint
setting. That's the way it works, the control head isn't all that smart.
The mixing flap inside the heater box is used to attempt a mix of air from
the heater core vs not from heater core, after it all goes through teh
evaporator coils for cooling.

The radiator fan should not affect engine warmup. If it doesn't warm up
enough for heater action just because the fan is running, then it sounds to
me like your thermostat (behind the water pump) is stuck open. The
thermostat is supposed to make sure the engine block and heater core are
toasty warm (like 180degF) before opening up to the radiator at all. You
should see an improvement in fuel economy and reduced engine wear (if you
could actually see that) with thermostat replacement, along with the good
heater function. The thermostat is like a $5-10 part but you might as well
do the timing belt, water pump, idler roller while you are in there.

HTH
Henry Harper
http://www.henry-harper.com hah at alumni.rice.edu
1991 200 quattro, 116k
1988 GTI 16v, 233k