fan controller

[npresley]

This is a message sent to me from a friend to help get him some info. any help and advice is appreciated. Here is the message:
"I read about this controller in the August 1998 issue of Classic Trucks
magazine. It came from Power Systems Management Co. in San Jose, CA. It
was/is called a "Variflow" controller. Their phone number then was
408-866-7944.

Supposedly, this controller had a 30amp fuse built in (upgradeable to 50
amps) and would not only turn the electric fan on and off, but vary the
speed of the fan to maintain the engine temperature within a specified
"window". Of course, the controller was adjustable between 150 and 240
degrees F (that's fairly common).

I have an adjustable controller on my fan now, but it doesn't adjust fan
speed. It has a temperature probe that's installed in the lower radiator
hose. I have a large core 19x31 Griffin aluminum radiator and want to keep
it, but I'm not against going with a different (better?) fan. Spal, Hayden
and Flex-a-Lite are among the better known fan manufacturers, but what I'm
really interested in at present is a better fan controller."
Thanks,
Nathan Presley

[Iggy]

Nathan:

I'm aware of a few 928s that have replaced their belt-driven fans with electric ones to restore some HP. Stock 928s have 2 fans: an electric one in front of the radiator (temperature-controlled) and the belt-driven fan behind the radiator (always moving, speed dictated by engine rpm). When eliminating the belt-driven fan, the front fan is replaced by a more efficient one, but I'm not aware of how it is controlled though I understand it works and requires the replacement of the control switch.

Edit: '87 models and up featured two small fans behind the radiator. I don't know whether this modification would work on those models.