No, the fan speed description is wrong. The A/C only has control over
low and medium speed. Low speed is selected whenever the A/C is on or
the radiator lower temp switch closes. Medium speed is triggered only by
the A/C high pressure switch. High speed is only triggered by the
radiator temp switch and then the A/C compressor is turned off
automatically to reduce the load on the engine and cooling system.

If medium speed is running a lot more than before, the pressure in the
system is higher than before.

Mark

Robert Lilley wrote:

>I have an early 88 Vanagon.  With a functional three speed fan.  AC system
>is 86 up but before the running mounting change in mid 88.  With the lower
>temp switch in the radiator.
>
>
>
>As I understand fan operation:
>
>
>
>Stage 1 on when AC compressor is engaged.
>
>
>
>Stage 2 on when the radiator switch kicks in or AC detects higher pressure
>and tries to reduce the pressure. AC still cools.
>
>
>
>Stage 3 on when engine too hot or AC pressure too high, AC clutch stops
>engaging and AC does not cool.
>
>
>
>I have had R-12 in the system before, but while in NC, I do not remember the
>2nd stage fan coming on within a minute of starting a cold engine and
>running just about all the time.
>
>When I had R-12 in the system (before I knocked a fitting loose and lost the
>R-12) and I lived in NC, I do not remember the 2nd stage fan coming on much
>when the AC was running, just the first stage.  The only time I remember it
>coming on was when the engine idled for a long time and ran hotter.
>
>
>
>I converted to R-12a after a shop put too much oil in the system and blew an
>o-ring out.  I do not remember the second stage fan coming on very much in
>NC and after I got the engine to run slightly above the LED in the hot
>weather in AZ (engine was lean). Still the second stage fan did not run when
>the AC was on.
>
>
>
>Well the R-12a leaked out to a pint that it stopped cooling, but the
>compressor still turned as the clutch engaged.
>
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>Is it just the higher ambient temps in here in AZ or is the system charged
>too much to cause the second speed fan to run all the time but not enough to
>cause the high pressure switch to cut the compressor out.
>
>
>
>The 2nd stage fan is running almost constantly� even when the engine is cold
>on a first start......
>
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>