Brown truck - 78 F150 351m c6 4x4

Perhaps 6 years ago, took the truck in for a/c work. I don't remember all they did, but they put in a new compressor and charged the system with Johnson's Freeze 12. Worked fine for a couple of years, then quit being cold. Took it back, and they re-charged the system. Good for another two years before it stopped being cold again. Took the truck back to the shop, and they said they could no longer obtain that refrigerant, and my only option was to convert to R-134

I didn't do the conversion, and I toughed it out for another couple of years. When I chenged the cam, I needed to pull the condenser, so I disconnected the hoses from the compressor. After I finished the cam job, I reconnected the hoses, but didn't run the system

I took the truck to a different shop and explained the history. They said the compressor, drier and expansion valve would need to be replaced. I bought those items, and changed the compressor, leaving the hoses disconnected

I returned to the shop, where they removed the expansion valve and dryer. They flushed the system, cleaned everything up, put in the new parts, and vacuum-tested the system. Everything tested good, so they filled-up the oil and charged the system with R-401a. Everything worked, and I had cool air for the first time in years!

The a/c guy said I should replace the fan clutch, as he felt the fan wasn't drawing enough air to keep the condenser happy. So I drove it home, and replaced the fan clutch with a severe duty f350 clutch. All seemed good in my world!

I drove the rest of the week, and the weekend, and everything was good. As I left work today, I kicked the a/c on, and it didn't seem to be getting cold...cooler than the 118 outside, but not cold. I pulled out as far as the driveway, and the truck stalled. I restarted the truck, and the a/c was warm and smelled odd. That's when I saw the blue smoke escaping the front left side...

What went wrong???

 

the compressor locked up and the smoke was from the belt slipping? or if you're lucky, the belt just needs tightened (you didn't mention if a new belt was installed, it may have stretched a bit if so).
does the clutch actually engage (and turn the compressor)??

 

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Was the smoke coming from under the hood or from the A/C dash vent?
If the vent, sounds like the evaporator has taken a dump, if from under the hood, like dlburch said, maybe the compressor has locked up or possibly a hose has blown out. You'll need to do a visual inspection.

 

As I understand it your compressor takes the evaporated coolant from the evaporator and compresses it into liquid - it is designed to take in vapor. When you change refrigerants and compressors it's a bit of a crap shoot as to how much coolant to put in - it could be 'way overcharged in which case a liquid slug hitting the compressor would lock it up and like dlburch said, your belt could be making the smoke. Could be your evaporator or let go, could be if you bleed off a bit of coolant things will work better - hard to say. If you saw a bunch of white vapor, though, most likely the coolant blew out and you have an empty system. Need to get the system pressure checked first.

 

Thanks, guys, for the suggestions. I won't be able to look at it until Friday or Saturday, but the smoke was definitely coming from under the hood. It was very light in color, although I smelled it in the cab before I saw it.

The belt was not new-it's been on there a while, so I doubt it stretched, although it's possible it glazed and slipped, but it was a pretty good cloud. I'm guessing it blew out.

Back to the shop...

 

ouch... that does indeed sound like it blew... had the identical experience once in August while driving from Maryland to El Paso. Made for a very toasty trip on vinyl seats.