I managed to pop open that little relay box in the engine well and spliced into it for the AC and it works perfect. Thanks for the pictures. I miss the days of carbs, i could rewire an entire car and pull the motor in an hour. With this truck there is probably 50 different wires going to the engine, my mustang had about 5. As for which one to hook up to in order to use the OD to shut the fans off im not sure, theres probably someone on here with a wiring diagram. But maybe its just me, but i know my truck goes into OD even while driving in the city when the roads arent as busy. I would think it would make more sense to either just leave them on or wire in a bypass switch.

 

Did you use the power on sense there as well?

 

No i used one inside the cab for that, that one was up by the column but i forget what color and stuff.

One thing i was thinking you could do for the highway is just have the thermostat set a little bit higher so the truck would run maybe 10 degrees warmer, but that way on the highway you would have enough airflow to cool things below that point without the fans. Its just an idea and i dont know if it would work out or not.

 

I stumbled across a company, DROPTAIL that has this eFan Controller.

I don't like the remote fan on/off but it may be easier than wiring something up inside.

Features:

Use with existing, as well as available contact and non-contact, temperature sensors.

Automatically turns off fans at highway speed for:
-Improved cooling by unrestricted airflow
-Reduced high alternator charging load
-Speed off override for an overheat condition
-Reduced aerodynamic drag caused by rotating fans
User adjustable/programmable via RF remote control key fob
Turn on/off fans remotely or while driving
(2) Adjustable ignition off cool-down timers
Alarms for no fan turn on detected, and overheating
Adjustable for (3) threshold temperatures, and vehicle speed off trigger
Fans turn off for engine starting
Audible beeps for user interface

I am not sure what the 'speed sensing' circuit the Droptail uses for turning off the fans at highway speeds.
I was thinking of maybe using a tranny trigger in third gear (highway speeds). Could that be done?

 

Hi.

Thanks for that link! Always nice to have options.

Mad's controller has similar features for turn-off at speed; forgot what sensing method was used.....

bubba

 

Ahh.. I finally read MEC's setup and he uses a 2 probe setup.
::Probe 1 is on the condensor to kick low speed at 180.
::Probe 2 is on the radiator and will kick on high at 205 (his personal setting) .

So really instead of tapping into the AC engaged line, it is just running a low fan speed cooling system for the AC <180 and high fan speed for the radiator/engine <205.