Originally Posted by compu_85

Yesterday I did a small modification to my car's Aux Fan circuit.



The box with the knob mounted to the ABS pump bracket is a temperature switch. It's designed for retrofitting electric radiator fans in place of a belt driven one. Here's where I got it: Amazon.com: Flex-a-lite 31147 Adjustable Temperature Control Unit: Automotive

I connected the switch into the stock high pressure switch circuit. The sensor bulb is zip tied to the high side line coming out of the receiver dryer. I put a piece of pipe insulation over it to shield it from under-hood temperatures. I put the dial for the fan switch on its lowest setting (which according to the manual is 180*F).

The switch works well, the fans cycle on and off at idle when the system is under high load. This, along with a new fan and clutch has my 134A converted W126 blowing high 40*s at idle on an 80* day. If I ever decided to make changes the whole thing is easy to undo and no changes were made to the car's wiring.

I've also toyed with the idea of using this switch to kick on the 1st speed of the fans (as it does now) and connect the high pressure switch up to the 2nd speed. I have a 110A alternator now, so it won't drain the battery as I sit in traffic.

Thanks,

-Jason