Sounds like the r134a is operating near the AC high pressure switch trip
points and is triggering the fan to go on high speed and then off as the
pressure falls below the trip point.  That is the extent of my knowledge on
this subject.  R134a does run higher pressures so maybe there is a different
switch that needs to go in which triggers at proportionally higher pressure
settings.

TEMiller
----- Original Message -----
From: "Roger Van Till" <rvantill@SBCGLOBAL.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, July 01, 2004 3:42 PM
Subject: AC conversion quirks

> My trusted mechanic switched my 89 Westy automatic over to r134 last
> week.
> Since then when I turn the AC on the fan starts up on low speed and two
> seconds later whips up to high speed,
> then continues to cycle the high speed fan on and off several times a
> minute.
> It never acted like this before when the system had freon in it.
> Is this a problem or is it the nature of the new refrigerant?
> This occurs whether the engine is hot or cold. I had a new water pump
> installed at the same time, but this is function ing fine my temps are
> normal
> and the fan comes on low when the needle climbs in traffic.
> Any Ideas?
>
> Roger Van Till
> '89 Westy
> "The Moose Lounge"
>