Can anyone who has done this provide direction ? I still want the A/C turn function but also the ability to fire it up "on demand"

 

you can use a wire from s13 terminal which is there already for a switched 12 bolts to a switch then directly to fan motor or go directly to the relay fan. I did this on my Subaru. I found if you energize the relay with a switch the ecu thinks there is something wrong. So you have to go to the line side of fan

I just used a spade connector to connect to the s13

 

@redwhitekat ah perfect thanks

 

I was thinking about this too, please report back if there is an improvement in coolant temperatures. I have one of those discos (03) that ticks above a certain temperature - usually 194ish. Don't mean to hijack your thread - but other things I have been thinking about
-Adding an oil cooler (sandwich adapter style)
-Upgraded radiator (I know alex_m posted about one from a GM vehicle)
-Electric water pump (helps with low flow state at idle)

I already have the inline thermostat mod with 170* thermostat, normal temps 178-186. Though lately has been running hotter up to 196 due to 90*+ weather (not running the AC). It appears the cooling system is not big enough for the 4.6 V8, would be nice to be able to drive around in hot weather with the AC on and not worry about coolant temps.

 

might want to check to see if "fan ON" is a negative ground to relay before wiring a POS to it....

 

@XRAD where is it fun in that, you keep the smoke in that way.

But seriously that is a good point.

 

yes...lol...keep the smoke in! Everything runs on 'smoke'! let the smoke out and it all falls apart...

 

Late to the party but it's worth mentioning that when switching 12v to power the fan (it is continuous ground) you should include at minimum an inline fuse, and if you want to get nuts provide an additional relay with a fused circuit. As those fan motors rust/bind with long periods of non-use, they will draw more and more power to the point that things could get melty. A 25A fuse should be plenty. You might let the smoke out of the entire truck if you're not careful! ;)