Ok I bought one of these to control the fans because I've had trouble with pin 41 of the EECIV losing control of the fans on my 351 powered range rover which has EL fans.

This thing works but, because i didn't have time to research it properly before buying, I'm paying the price now.
As I said it works at controlling the fans but it has several problems.

1. You can set the switch-on point easily using the buttons on the gauge but, there's no hysteresis adjustment.

2. There's a separate relay box for controlling the fan which would be ok except it's not weather proof which means a fat power lead needs to run inside the car and back out again to power the fans!? Dumb!
So I modified the circuit board to just switch the low side of the EL fan relays.
Another stupid part of this relay box is that they could have sensed the power was going to the fans but instead the "ON" led just shows that the gauge has switched it on.....doesn't mean the fans are actually running

3. The digital display is bright white and not dimmable!? So you actually have to cover it up at night because you can't see the road!?

4. The back light of the display has changeable colours but it's pointless for a couple of reasons; first, the ultra bright digital display means it's pretty hard to see it anyway and worse, IT DOESN'T STAY WHERE YOU SET IT!?!!! Turn the engine off and it goes back to the original colour every time! WTF!?

Hello,

I would use a capillary tube switch, and have an over-ride and disable for water crossings. A viscous coupled fan is better IMO because they can move a lot of air. Low speed / range with a lot of drag such as climbing a sand hill, you will need as much air as you can get through it. I like to keep things simple, less to go wrong a long way from home and easier to fix.

You could set up 2 Capillary switch's 1 to turn Fans on and the other to turn them off. The Aircon also needs the Fans, so a few things will need to be planned for. Nealy 40 years ago I had a small truck with a thermo, I could normally drive to Sydney without the fan coming on. If it did, it wouldnt turn off. It seems that at Highway speed it was actually slowing down the normal air flow !