Dual electric fan conversion
Having got the fan assembly installed, it is time to wire them up. When both are spinning, the draw is 50 amps so this has to be done carefully. It is important to check the ampacity (ie. the current carrying capability) of the wire used to be sure it doesn’t overheat and melt. 8AWG wire with a THN heat rating will carry 50A. The 10AWG wire supplied with the fan carries only 25A continuous.
In terms of fan control, I chose a Derale PWM controller #16795. This controller varies the fan speed to minimize current draw, deriving its data from a brass probe inserted into the lower right (passenger) corner of the radiator.
I started by fabricating a shelf to carry the controller module (which I am gripping in this picture) along with a 50A circuit breaker (alongside the module) and on the underside, the two shunts (easier seen here) to allow me the measure the current being fed to each fan (later project).
The picture at left shows the shelf with the module, circuit breaker and shunts mounted on brackets so that it sits between the fusebox (rectangular black box) and the windscreen washer bottle.
Having wired it all up, the module turned out to be completely DEAD. All that time wasted. So I hastily wired two 25A relays in, one per fan, for manual control from the driver’s seat. I will try one more module and if that fails, I’ll go another route.
Despite the fan controller being DOA, with manual control, I could test the system on my test route. (Note that I am running RO water plus Water Wetter in the radiator - not antifreeze). On the run, the coolant ran about 10 deg cooler than before. On hills, both fans were required. When stopping at a light, the fans drew down the coolant temps much faster than the stock fan, since at a light, it would be sitting at tickover and moving very little air. Whereas the dual fans are running at full tilt.
The engine oil and tranny oil ran 20 deg lower than normal because the fans are drawing air through both coolers very effectively. So all in all, a worthwhile mod.