I just found the schematic on line and they are already using engine
temperature to control the fan. I thought they would since VW is a excellent
company.

This being the case, something may be worth designing that turned on the fan
earlier based on temperature change, like for example when pulling a hill,
to give the cooling system a jump start on cooling.

Tom
www.towercooler.com

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf Of
Mike "Rocket J Squirrel"
Sent: Sunday, April 25, 2010 10:18 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: PWM controller , was Water Cooler System Design Flaw
Workaround?

Alistair Bell wrote:
> my rad fan is 450 W if that helps
>
> alistair
>
> PS i dont see the point in a pwm controlled fan, I would concentrate
> in a more sophisticated temperature interpretation, ie a PID
> controller... monitor rate of temp change to that fan can keep on top
> of things...
>
> but you know, my experience of the fans in real life is that they come
> on, cool the van down and go off.... seem to work fine :)

I'm with the Bell on this one. The radiator on the fan is capable of
creating lots of cool water, and the thermostat opens and closes as needed
to draw from that reservoir. If the engine was seeing huge over and
undershoots in temperature then a better control system would be warranted.
But the large thermal mass of the engine pretty much assures that temp
changes will occur pretty slowly, and the thermostat seems capable of
keeping up with them.

I guess I don't see a problem that needs solving. But I do enjoy fancy
engineering for engineering's sake, too.

--
Mike "Rocket J Squirrel" Elliott
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Westrailia: (Ladybug Trailer company, San Juan Capistrano, Calif.) Bend,
OR KG6RCR