[calamity]

Here are the symptoms, after hauling a heavy load of hay for approximately250 miles the AC ccuts out and starts blowing warm air. All the gauges were reading normal. We stop and eat and after about 1 hour we get back in the truck in the truck and its working fine until we travel about 100 miles then no ac again. 3 Days later we make the 500 mile trip back home empty trailer and ac works fine all the way home. Recently the truck was reflashed, could this be some kind of tuning strategy from Ford or an issue with the latest reflash?

 

[RT]

What are you driving? One of the biggest culprits behind the issue you are describing is increased air gap as a result of AC clutch wear. The gap gets to the point that the clutch magnet can't maintain engagement. The solution is to pull the front hub and remove the spacer. Alternatively, you can buy a new hub for about $25 (available at Tousley Ford or RockAuto). Here's a link that shows you what to do:

SpringerPop's Compressor Clutch Air Gap

 

[calamity]

03 F350 with 6.0L, truck has 142,334 miles on it all stock except for ARP head studs, muffler delete and timbren overloads.

 

[calamity]

Pulling approx 20,000 lb load of hay

 

[grumpy old man]

The next time it happens pull off the road and see if the compressor is turning. If it is not then you need to diagnose why, if it is then you have a whole different problem. But in the mean time I'm with RT check the clutch clearance.

 

[dikkstarr]

Mine shuts off when the oil/coolant temps get to be over 230, then its kinda half on until it cools down a little. Also I read somewhere that if the high pressure side in the ac system gets too high it shuts down. Maybe the programming is turning off the ac to help cool the engine during high load high heat events??