i had a recent issue that was similar...
ended up that the wire to the fan temp switch was grounding out.
the low setting for the fan was getting blown so when it turned on,
the fan was on high and sounded like a jet engine.
engine had been running hot for a while...
ended up running thru 3 radiator fan temp switches before the
wire problem was id'd.
might be worth your time to drop in a new $14 switch?

On 1 May 2014 09:49, Project Pat <psdooley@verizon.net> wrote:

> The rad fan is triggered by the AC on most vehicles.
> Check the wiring diagrams to confirm.
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> TCollins
> Sent: Thursday, May 01, 2014 11:56 AM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Radiator fan switch wierdness
>
> I wondered about that too. Since the fan does trigger from time to sporadic
> time.
>
> Would any other switch trigger radiator fan operation?
>
> > On May 1, 2014, at 11:22 AM, "Project Pat" <psdooley@verizon.net> wrote:
> >
> > Just a wild guess, you may want to take it out and check for buildup.
> > Junk on the coolant side of the switch could insulate it and cause
> delayed
> > reaction.
> >
>