Issue with A/C at anything over idle

[OuttaMyWay]

Helping a buddy with his '17 Winnebago with the Ford v10 F53 Chassis.

Back story:

He bought it and it would blow extremely cold to the point that after 30 min, the coil would freeze up. After stopping the engine, it would thaw out but it would not thaw by simply turning off the AC.

Took a look under the rig and noticed that the clutch was never disengaging on the compressor. took out the center bolt and tapped on the clutch and was able to work it free. It looked to have been rusted in place. cleaned up the mating surfaces with some emery paper and reinstalled the clutch and at idle, all was well. pressures looked good and it cycled on and off and a decent interval and duct temps were in the low to mid 40's.


Now here is the kicker. If you increase the RPMs to say 1500, the clutch on the ac will engage for like 2 seconds and then immediately disengage... wait 10 seconds and it repeats.. the pressures will drop as the compressor never stays engaged long enough to bring them up and the vent temperature climbs back to ambient temp. slow back down to idle and it engages just fine, cycles as per normal and the temps and pressures return to normal.

Both the high and lower pressure switches have been replaced and the refrigerant load is per spec as he had it evacuated and refilled to factory levels.

It is as if something is telling the clutch to disengage at higher RPMs due to slipping or something non-pressure related.

Any Ideas? I hate to tell him to start shooting off the parts cannon since at idle, everything seems to be working perfectly and only fails when the engine RPMs and not system pressures are elevated.

[tbirdtbird]

We thrive on actual pressure readings....no other way to go.
1. Did this vehicle sit for a long time to have that much rust build up?
2. get a set of readings (hi and lo) at 1500-1800 RPM, max fan, max cool, windows open, recirc on. ie max load conditions. Also record ambient. Post all that so we can see, along with vent temp.
3. I am a bit suspicious of the clutch gap, should be .020 (business card). The rusted condition could have interfered with what the gap is supposed to be. That clutch mechanism sounds like it needs to be cleaned/wire brushed, or otherwise cleaned up a lot.
If the gap is too large or the clutch is sticky (dirty) it can engage then disengage. It can even disengage totally until the engine compartment cools off and then reengage, but this latter scenario is not what I think is going on

[DetroitAC]

Our thread starter isn't going to be able to get that data, it doesn't stay engaged very long at 1500 RPM.

Please put gauges on it, and do your best to describe what the gauges are doing.

Also, could you describe the hardware? What is the compressor, what is the HVAC unit? I'm guessing the compressor is whatever Ford usually bolts to their V10, my guess is a big fixed swashplate compressor, like a 200cc. But what is the HVAC? Is it a Ford unit from Super Duty trucks or maybe an aftermarket unit?

[JohnHere]

Both the high and lower pressure switches have been replaced and the refrigerant load is per spec as he had it evacuated and refilled to factory levels.

Another thought: Depending on when it was evacuated and re-charged, it's possible that the system has a leak and the refrigerant amount is no longer up to specs. It would be interesting to recover the charge to determine how much refrigerant is currently in the system. If it's low, then we know that the system has a leak that must be found and repaired.