First post here, spent 20 years as a tech at a parts cannon shop, the shop owner "diagnosed" (pattern failure) every thing and i only got to do testing after he was wrong, anyway I opened my own shop 2 years ago and am trying to become a better tech.
I'm Struggling with an Ac diag on a 2020 ford transit 350 with 3.5 ecoboost.
Came into the shop with a complaint of AC inop, r&r 1.87lbs of 134, test drive and ac gets cold while driving and warms up while at a stop, cooling fans not working, replaced defective fans, fans working properly now, ac blows 40 degrees out of the vents at idle.
I take the van for a test drive to verify and ac almost immediately goes warm. I pull it back into the shop, shut it off and scratch my head for a bit, fired it back up and ac was working great, hooked gauges up at idle in 70 degree shop, 30 on the low side, 125 on the high side (seems low to me) with 40 degree vent temp, let it sit there and idle for a couple minutes and its still blowing cold. Drive it again and ac cuts out almost immediately again, pull it back into shop let it idle and ac begins working again.
Pull freon out, change expansion valve (old habits die hard) and vacuum system for 3+hrs thinking maybe theirs moisture in the system, van looks to have recently had the front timing cover removed and maybe another shop had the system sitting open.
Charge it back up and same deal, I realized at this point i could make it act up by revving it in park, rev it up and the low side begins to drop, it will drop to almost 25 and then like it hits a low pressure cut off switch will start to creep up to 55 and high side drops to 100, compressor is engaged this whole time, I let it idle it will eventually go back to blowing cold. It seems like if I cycle the key that fast tracks the blowing cold air. Letting idle seems to take 3-5 mins to return to cold and a key cycle seems to take less than 3.
Two things that I notice are the compressor clutch is always engaged whether its blowing hot or cold, and their is no condensation coming out of the evap drain.
The parts cannon is starting to lock onto the ac compressor or think that i got a new defective expansion valve, but im not sure what other tests I can do to verify that is the issue.
Thank you for reading my novel, any and all suggestions on what to test next are welcome and if im missing something obvious be gentle on me lol
