So clutch doesn't engage and compressor is not running. I have 12-13v at the low pressure switch and the same at the high. When I jump the low pressure I don't get any voltage at all at the plug that controls the relay for the clutch.

Where I'm confused is:

Is this a low pressure problem - gauge is reading 60psi on the accumulator

Or

Is this electrical somewhere?

Cheers

Simon

 

No, the low side switch only requires 40-45 psi to close. However, a pressure of 60 psi indicates the ambient is under 70F or the gauge is defective if it's appreciably warmer when you checked it.

Maybe, maybe not. You haven't told us what you're working on nor have you indicated you've checked the clutch gap (mechanical).

????

 

Sorry , yes more info. So it's a 2001 7.3 diesel F250. Clutch gap is barely 040 with feeler gauges and that seems to angle the clutch plate when I insert the gauges so it's only just over 030. The electrical plug I was badly trying to describe is the one that sits into the side of the compressor juts behind the pulley and I guess activates the clutch relay? it comes off the same section of wiring loom as the two pressure switches. On my step daughters 4.2l this plug measures 12-13v when AC is on. There is no voltage on mine when the AC is on. I also checked the 10A fuse which is good, so is the diode, I haven't checked the relay as on this truck it seems to piggy back the blend door and some other items and the blend door 'appears' to be working - although even on cool the air coming in is pretty warm but definitely gets warmer when you turn the heat up. I'm not hugely experienced with this and have been trying to work my way through - electrical is not my strong suit. thanks heaps for the help!

 

On an 01 diesel Super Duty, there's no AC clutch relay. The clutch is controlled by the simple series circuit of:

BJB F24 (HOT IN RUN) > Mode switch > Low Pressure switch > High Pressure Cutout Switch > Clutch coil > Ground.

Perform continuity and voltage checks to isolate. With power off, you can run a quick continuity check from the high pressure switch tan/lt green wire to ground and check for continuity through the coil to ground. You should read several (3-6) ohms through the coil.

The diode won't cause a non-engagement except if it shorts and blows F24.

It's very common for the crank sensor to be confused with the AC coil connector. Be observant. If you unplug it and the engine won't run, you got the crank sensor.

 

Thanks, I'll do that today hopefully! It is definitely the clutch coil connection as the engine runs with it disconnected. I'll let you know

 

So I've had some success with your help - thanks heaps!! found the ground wire further down was u/s so solved that and the compressor kicks in. The problem now is the clutch is cycling and on the bodget gauge I have it appears to be tripping on high pressure. Bordering on green to red - it's just a gauge off one of the fill bottles from autozone. I'm thinking now I shouldaybe just drop down an a/c guy to check the charge?

 

Go back and re-read the FAQs.

 

Ahh yep got it, I'll let you know how I go!