99 Peterbilt A/c cycling on and off

You wanna guess, I wanna diagnose.
"The guy probably doesn't have recovery equipment, and has ALL the signs it's low on freon."
Of course he does not have recovery equipment. Why I suggested if he did not take it to a shop to compare what he put in to spec.

"ALL the signs it's low on freon" You're saying that a high side reading of 325 (which is good and should be 300-350) is a sign of a low charge? So low that it causes the compressor to cycle rapidly, but also very erratic? At one point the compressor stays engaged for almost half a minute. "telling him different crap"
What do you think the pressure gauges are for?

Below is a post on TTR from a driver with a KW and his truck is blowing 39F out the vents.
"It has an expansion valve system. I have it charged to where the fan cycles on when the high side rises to 320 Psi.
With the fan on, pressures are 25/150 until the high side rises and cuts the fan on."

Geez, OP has exactly these readings. So you now gonna tell me the KW is also undercharged?

You and @Rideandrepair are fixated on the compressor clutch.
Hopefully OP gets back here and tells us how much he put in and if he tried anything else.
I'm thinking low pressure switch.

 

Goodness man! You mad?

Could be, maybe not. 39* ain't nothin special.

Dude, I'm not hittin google to come up with replies, and I'm not searching old threads for validation.

Calm down, grab a cold one (can of freon), and enjoy your day

 

You’ll know if it gets overfilled. Assuming the high pressure switch is working, it’ll rapid cycle also. Similar to when it’s low. I made that mistake once. Added a can upside down, in liquid form when it was full. Split the casing on my perfectly good Sanden compressor. Glad yours working now.