Hey guys. I've been a long time lurker of the 6.0 thread, being I didnt have much to add with my lack of experience on the 6.0 this is my first thread. I've spent numerous hours searching this forum and powerstroke.org forum so not to be that arsehole who asks the same question others already posted about.

My AC compressor locked up on me last week, pulley wouldnt budge & had to change it in a parking lot because the drag on the serpentine belt wouldnt allow enough crank to turn over the 6.0. Oh and I was towing 15klbs too.

I swapped the compressor (new w/ pulley) and left the AC off until I got it to a shop where they flushed the AC system, installed an orifice, accumulator and 42oz of freon. Heres the symptom: The low side pressure builds to 40psi and holds there while the high side creeps all the way up to 350psi at that point the compressor shuts down until the pressure drops down to about 250 and the compressor turns back on. It continues through this cycle. The cabin duct temperature was 50 degrees while driving down the interstate.

I took the truck back in thinking there was a restriction on the high side (probably a plugged condenser) so they evacuated the system and I took it home and added a new condenser, orifice and accumulator. At this time I found a lot of oil in the accumulator. I checked the receipt and they added 9oz of oil after I requested they didnt, so the system had been overcharged on oil. When I took the truck back for them to recharge, I reiterated NOT to add any more oil.

The first orifice had a little bit of gunk, maybe 25% of the screen with no metal shavings. The second orifice had some shiny metal shavings, not much though, so it got changed a third time. The cabin duct temperature dropped to 45 degrees while going 45mph, so it is definitely blowing cold.

Im at a complete loss, shop doesnt know what to do. These symptoms do not make sense to be a plugged evaporator, a bad pressure switch or a clutch relay. Could this be a bad evaporator temperature sensor? or something I am unaware of? Is there a way to scan the PCM to see if there is a faulty sensor?

Thanks a bunch, I've always found good value in the threads on this forum.

2004 F350 Lariat 6.0 DRW 4x4 full bulletproof.

 

There's still trash in the system. I can guarantee it. Did you change out the reciever/dryer?

 

Ya, its been changed out twice now. It would certainly help out troubleshooting if I had a vac pump to pull the freon in between swapping components. I'd give credence to swapping the high pressure line from the compressor to the condenser, but its $100 per evac/charge at the shop, plus its not good practice to reuse the accumulator/dryer so make it $140 each time..

 

Sometimes it's cheaper to pay a shop. If it takes them 3 tries it's on their dime.

 

Never been in a Ford AC system but the GM systems use to have an inline filter to catch the debris when the compressor failed. This filter had to be replaced or you would get very high compressor discharge pressures. I had the same thing happen on my old '87 Chevy 6.2L Diesel Suburban. Look for a bulge in the hard lines around the fittings. A Ford HVAC diagram should call it out.


ED

 

Thanks Ed,
Post 90's systems have an Orifice tube. It is a filter as well as an expansion valve, replacing the need for the two separate components, although I believe some newer AC systems that require even less pressure at the evaporator may still have an expansion valve. Anyhow, i've swapped mine out a couple times now.

I think my next step is to replace the high pressure lines from the compressor to the condenser and i might as well change the line from the condenser to the accumulator. When I changed the orifice tube at the same time i replaced the compressor, there was a little gunk but no metal flakes. When I swapped it the second time while I changed the condenser about 200 miles after changing the compressor there were fresh metal flakes on it. Not much but there was some...