Its been a while since I’ve touched a T2000 but follow the high pressure line back from the condenser and you should find 2 pressure switches attached to the line these are the binary and trinary switches. One switch will control the engine fan and the other will control the a/c compressor clutch. I know they are there for sure on a W900 and if I remember right the T2000 has them too.
You can test the circuit with a jumper wire. Unplug the fan switch and the fan should engage when the circuit is open and disengage when you insert the jumper wire. Unplug the compressor switch and the compressor should disengage with the circuit open and engage with the jumper inserted. You really need a/c gauges connected if you do this so you don’t let the head pressure get too high.
Next look on the driver side of the coolant reservoir. You should see a low pressure a/c line with a low pressure switch attached to it. Im not sure about testing this one because I think it has 3 wires, but like I said it’s been a while since I’ve worked on one.
If your engine fan is working properly and the compressor is cycling your switches are probably good. Check to make sure the condenser is clean. If air can’t pass through and cool it the high side pressure gets too high and the compressor will shut off.
Also if the refrigerant is low the low side pressure falls too low when the compressor comes on and the low pressure switch cuts off the compressor.
Have you hooked up a set of gauges to the truck to check the pressures and see if you have a blockage in the system?
2002 6 speed, Edge Drag Comp, DAP 100s, Phatshaft 62/65-14, ARP 425's, Valair Kevlar/ceramic single, FASS 95