On Wed, 8 Oct 2003, Felder wrote:

> It has occurred to me, during all this head and coolant replacement,
> that I have never heard the radiator fan come on. That would probably
> explain the high-side temps at idle and low speed.
>
> What's a good way to test to see if it the fan, the sender, and/or
> anything else involved?

Do you have the '82-only radiator with the two switches, up behind the
upper grille?  If so, short the two terminals on each switch in turn.
One should give you high speed, the other should give you low.  (The
quickest way to do this is to push back the rubber seals and just wedge a
screwdriver between the terminals.)

If both speeds work that way, you may have a bad switch.  If one speed
doesn't work, it's either the wiring or the fan motor.  The low-speed
resistor is part of the motor on '82s.

Because these switches are mounted high, an air pocket in the radiator can
also keep them from tripping when they should.

Keep in mind that the fan doesn't do anything when you're on the highway.
The ram air through the radiator is greater than anything the fan can
push.  If your temperature creeps up too high in traffic, suspect the fan.
If you're running hot at 55 mph, it's not the fan.  Also, the radiator fan
doesn't seem to come on very often on diesels.  The only time I've had my
low speed fan cycle is when I was sitting in traffic for half an hour in
80 degree weather.  In 50 degree weather like we're having now in
Michigan, the radiator never gets hot enough to trigger the fan.

Bentley says that +/- one needle width is normal variation in the
temperature gauge from van to van, so it's possible you aren't really
running hot.  You should buy or borrow an infrared temperature gun (~$50
at Radio Shack, I think), or install a calibrated temperature gauge to
find out for sure before you start worrying too much.  You simply CAN'T
determine ANYTHING absolute from the position of the needle on the stock
gauge because it's NOT calibrated in any way, shape, or form.  If it
starts reading higher or lower than normal on *your* van that's
meaningful, but comparisons to other people's vans are not.

David Brodbeck, N8SRE
'82 Diesel Westfalia
'94 Honda Civic Si