Peterbilt 325 fan clutch

I'm the shop mechanic for a local company that has a small fleet of PB325 with paccer mx-6 with Allison transmission.
I've ran into a problem on one of the trucks. For some reason the electric fan clutch won't turn on when I turn the switch on.
I checked the relay in the engine compartment & I'm only getting power from one yellow wire. The relay plug was four wires, yellow wire with power source, yellow going to the fan clutch, orange wire that suppose to have power & white with green strip going to fan clutch. For some reason I can't get any power from the orange wire. I followed the wire harness to two pig tails that was wired backwards and I'm still getting no power. Then the wires go into a big wire loom. I've got power at the switch inside the cab, but I'm not getting any power in the engine compartment. I checked the fuses under the steering column & left kicker panel and they all checked out.
The company doesn't want to buy the repair manuals for them, so I'm flying by the seat of my pants. T
Thanks for any help

 

I already jumped the fan and it works. I thought the fan was the culpret at firs, until I checked another truck. They cut up the wire harness for the a/c compressor so it wouldn't work, they don't want the drivers to get to comfortable.
I'm going to pull the wire loom apart and follow it to the fire wall and go from there and also check the a/c compressor for any bad wiring jobs, the previous mechanic wired the pig tails wrong.

 

I'm not sure how irrelevant this code is, engine fan clutch output device driver voltage above normal or shorted to high source. 6473SPN
Seems like I'm getting power from the firewall.
Im learning something new everyday with these trucks.