Re: heater in and out...

["Polands" <polands@xxxxxxxxxxxx>]

Tom,
My guess is that you may have two unrelated things going on.  The hot or
cold sounds like you need to either replace the solenoid valve or renew
it's interior bits.  The valve and the screen in there get corroded or
gunked up and sticks.  You can replace it for about $30 as I recall.
Its on the firewall, driver's side.  About 1" x 1" x 3" with both heater
hoses and a top mounted electrical connection.

Bentley says to "turn the key on with the engine cold.  Slowly turn the
(temp control) knob clockwise starting from it's coldest setting.  When
the temperature setting on the knob reaches the car's interior
temperature, the valve should close, making a sound like a light thump.
To check the automatic function of the valve, turn the knob to a
slightly warmer setting and listen for the valve to pulse on a and
off..approx every 4 seconds."

This seems like the most common heater problem.  Before replacing it you
might try first just pulling the plug, undo the 4 top screws, pull out
and clean the pieces and reinstall.  There are other pieces that can
fail, like the heater core temp sensor, solid state temperature control
unit, interior temperature sensor, and the air distribution flap
controls.

All are covered pretty well by Bentley, highly recommend getting this
book even at full new retail cost, it will pay for itself in very short
order.

Not knowing what the smell was like, I'll offer a couple things to look
into.
Both have to do with the fan.   If your heater fan only runs on high, or
does not clearly run at three different speeds, then you should check
power delivered to the fan to see if you get 3 different voltages
depending on switch setting.  Bently says if you only get 12-13 volts
then you've got bad resistors.  If it squeeks or only runs well on high,
then I would also open up the fan compartment and work over the bearings
with WD40 to clean them out, and then apply a good light oil.  Be very
careful with the in-out work to avoid bending the shafts, replacement of
the motor/fan bit is about $200!!!.

Hope this helps.

Steve Poland
'88 535is
Portland, OR

Original message;

Subject: heater in and out...

The heater in my 1988 528e runs like my boss... hot and cold.  I did
notice a
weird little smell for a time

Tom Borden
teborden2@domain.elided>

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