Hi all...I am new to this forum. I bought a 2003 Ranger, low miles one owner, really nice and well cared for. The only thing is that it did not come with AC from the factory. I am adding AC from salvaged parts and new parts. I understand how to do it mechanically and I understand how the pressure switches work. I don't understand how to wire it. Oddly the wire and plug for the low pressure switch is already there. I have to add the wiring for the high pressure switch and the compressor. The ac clutch relay and fuse are also already there from the factory. I replaced the dash control panel to one with ac selections and it works fine. Not sure where to go from here. Also there is a two wire plug with a cap on it that is attached to the passenger side of the fan shroud, One black wire and one blue wire, capped off and unused.

 

Welcome to the forum

Not sure you will be able to wire it like a factory AC system since the engine computer(PCM) is what controlled the AC so not sure if that software would be in a non-AC PCM vehicle

The way the factory AC worked was when the panel was in any position except OFF or VENT, a 12volt "AC Demand" signal was sent to PCM pin 41
The PCM would then use an Internal Relay to connect the pressure switches GROUND(pin 86) to the AC relay coil's ground(pin 69) and AC relay would close and activate clutch

If you have a Ranger model with electric cooling fan then PCM would also activate(ground) that relay at the same time(pin 45)

Diagram below

You can add your own relays to by pass the PCM, some have had to do that when the PCMs internal relay(or software) has failed, not common but has happened, and it does get expensive to swap out PCM and have it reprogrammed to match vehicle for just 1 faulty relay

 

Thanks for your response Ron...I suspected that regarding the PCM. If I build a new circuit with a new ac clutch relay would I have to include a WOT switch as well. Also would I have to use a toggle switch to activate the AC or is there a way to use the factory AC selector?

 

Thanks for your response Ron...I suspected that regarding the PCM. If I build a new circuit with a new ac clutch relay would I have to include a WOT switch as well. Also would I have to use a toggle switch to activate the AC or is there a way to use the factory AC selector?

 

You would need to look at the panel wiring to see if the Purple(violet) and Grey/yellow(12v) wires are there, if so then you would need to find that purple wire in the engine bay, it would run to the PCM
If they are not there then you will need add them, pin in the new wires on that connector, a 12v key on wire and 12v out to engine bay, the AC panel itself will have the correct contacts internally

With the 12v "demand" signal you can then wire that to the coil of a 30amp relay, and hook that coil to the pressure switches ground, so if a switch "opens" the relay would open and shut AC compressor off
That relay would pass a fused 20amp 12v wire to AC Clutch to activate it

12v key on------Panel---------------Relay Coil-------------high pressure-----low pressure---------------------ground

Full time 12v----20amp fuse---------------------Relay------------------------------AC clutch-------------ground


You can add another relay to active cooling fan as well when AC clutch is activated

WOT(wide open throttle) relay was a convenience not a requirement, it shut off AC when driver wanted maximum power for passing or ??, so when gas pedal was pressed down to the floor(WOT) AC compressor would be shut off until pedal came back up a bit
You could always turn selector to VENT or OFF if you wanted max power

PCM would also shut off AC if engine was overheating, again a convenience not a requirement, you have a dash Temp Gauge, so......................

 

Thanks so much Ron...You have helped me so much. I can't thank you enough