A/C System diagnosis

It's the A/C season but I've not had a lot of experience diagnosing system faults since I did my training and course back in 2015. My routine is sketchy at the moment and working where I work does not lend itself to help. I seem to be given hour slots and must prove everything within an hour or it goes out to the auto electrician who can keep the vehicle for hours or days to fix them!

So today I was asked to inspect the above A/C system and I was lead towards the understanding that the compressor had failed?

I've gone about this diagnosis the wrong way round on this occasion... 

I decided to test for a voltage feed to the compressor. 0.08 v is all that was present on both wires at the compressor clutch. I traced the wires back to the relay which AD refer to it as a WOT relay. I was confused, a Wide Open Throttle relay wired into the A/C system?

I had no research material or technical data other than AD at the time so I was kind of thinking AD might of made a typo error?

This evening I've researched the WOT relay and now I understand that the WOT relay is the A/C relay also used to disengage the compressor clutch under wide open throttle conditions when hard acceleration takes place.

So I tested the relay anyway and found nothing wrong with it. I tested the battery supply to terminals 1 and 3 and both voltage supplies were correct. I further tested for a ground/switched earth from the ECM and found that approximately 5 V was on the earth line. I didn't get the chance to test for a short circuit from the ECM to the relay but had my doubts that such a wiring fault could be present anyway. I thought about the pressure switches at the last moments before home time so I decided to put the scanner on (should have done this first). A fault code for the A/C circuit relay (WOT) was present. No surprise there then.

Because I won't get the chance to see this diagnosis through to completion I thought I'd do this write up and see if anyone had experienced this fault and whether it could be caused by the pressure switches/circuits (there are two fitted) or the actual ECM would be the most likely cause?

I did however bypass the WOT relay terminals 3 and 5 but this did not permit the compressor clutch to activate, hence I was then wondering if the ECM is not receiving some input(s) and disabling the operation of the WOT relay?