I believe the radiator fan runs at a certain temperature, and that the high speed comes on at a still higher temperature.  Yes, it is tied to the air conditioning (if applicable), so that it runs all the time if the air conditioner is on.  mcneely

---- 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.
> >

--
David McNeely