Is anyone having trouble with their AC in the truck. I turn my ac on and as long as I let the truck idle for a few
minutes, I get cold air. Once I get going down the road the ac will stop cooling, it does not get hot, but it is not as
cool as it was when the truck was idling. Don't know if the compressor is the problem. I replaced the dryer and the
orafice tube, that helped a little. Anybody got any ideas? Thanks
 
Guess,too much head pressure,over charged,or the belt is slipping,
or all the above.
 
What does it do if you hold the engine at a fast idle while sitting still, maybe 2000RPM or so? It would be a good time to monitor pressures if you know what your looking at, and maybe have a way to accurately verify the level of refrigerant.

I have seen several of these trucks have weak clutches on the compressor, causing them to kick out or slip at higher RPM, they wont slip too long before you will notice burning paint and wear on the clutch hub though. An often overlooked thing is dirt/debris clogging up the condenser or other coolers behind grill. I have even seen debris get between the coolers/radiator etc.
 
Find a set of gauges with long hoses and monitor the high and low side pressures when it mucks up, and post back.
 
I have a 99 250 and my AC quit once. The clutch would not engage. I thought the magnet coil was gone but it turned out it was just the clutch's air gap. If it's a little too big the clutch will not pull in. The single screw in the center of the clutch has a shim washer that controls the gap. I took it out and it's been fine ever since. 223K miles and I haven't had to charge it in 5-6 years.
 
My 99 and 01 F250s both had troubles with the electrical connector for the clutch causing similar trouble. Vibration loosens the fit over time plus corrosion.
 
I can name a couple of other things to look at.....
First, did you evacuate after changing the orifice and dryer? Did you add oil?
There are many things that can cause the condition you describe.
Air in the system. Air will not compress into a liquid at the temperatures and pressures found in an automotive air conditioner system It WILL hinder the cooling process.
Too much oil will also cause the system to lose its effectiveness. When you change a major part like a dryer, it is possible to add too much oil to the system.
Another possibility (remote) is the throttle position sensor. If it signals a high throttle opening, the CPU interrupts the compressor circuit to allow full power to go to the wheels. This will usually cause a trouble code, but may not always.
Under charge or over charge are also possibilities. If overcharged, the refrigerant evaporates past the evaporator instead of inside the evaporator. Under charge causes the refrigerant to evaporate before entering the evaporator. Correct charge is important.
A clogged condenser can allow too much of the refrigerant to remain in the gaseous state as it passes through the system. This condition would most likely be more pronounced at lower speeds.
Evaporator icing can also be a cause of your condition. This is usually a result of undercharging. A plugged drain tube can add to this problem.

As you may be able to see, there is no short answer and maybe not even a single answer to your problem. Keep checking things and you will eventually solve the mystery.
 
I'm not there and can't see your system but in my experience 40 is too high. It needs to be closer to 30. That's with reasonable RPMs on the compressor.

I like tractors. The orifice systems I find harder to get the right charge on.

RT (my 2?)
 
The real question is how many lbs did you add after evacuating the system? I believe those systems take 2.63 lbs of r134 but there should be a sticker to verify as my memory may be off. Overcharging can certainly give the symptoms you speak of as the compressor running at idle would let it circulate more slowly.
 

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