The lowest of the speeds is actually from the AC running when the compressor
is engaged. There is very little difference when the radiator switch turns
on the fan as compared to the AC running the fan.

Either the AC or the radiator switch can call for the high speed. If the
radiator calls for the high speed the AC compressor gets disabled. There is
also a high pressure cut out for the compressor if pressures still get too
high. If the AC regularly calls for the high speed fan the system may be
over charged, especially if using R134A. You cannot reliably charge these
systems using pressure gauges and the sight glass. You need to fully
evacuate and fill with the proper volumne of refrigerant and it should work.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Richard A Jones
Sent: Tuesday, July 16, 2013 1:18 PM
To: vanagon@GERRY.VANAGON.COM
Subject: radiator fan speeds vs AC

I realized I don't understand the three speeds of the radiator fan when the
temp sensor only has two outputs.

I'm looking at Bentley 97.141 for my '87 Syncro Westy and the way I read it
is:

AC off:  radiator temp sensor runs the fan at low speed or high speed,
according to the 95 C switch and the
102 C switch.  Fan never runs at middle speed.  The low speed is via the
resistor and the high speed via the 3rd stage relay.

AC on:  fan runs at low speed, unless AC high pressure switch closes and
then it runs at middle speed.  This via the 2nd stage relay (tracks 14 and
22)  But when the AC clutch is running, fan always runs at high speed.
(Tracks 17 to 18 to 20)  Is this correct?

I don't think my AC does this; if that is how it should work, I'll have to
figure out why mine doesn't.  I know my fan runs at low speed when I turn on
the AC.

Thanks,
Richard