What would cause my ac pump to cycle on and off at about 4 or 5 second intervals. If I hold it at a steady rpm I can hear it cycling on and off every 4 or 5 seconds and consequently it doesn't get very cold in the cab. Now I must say that the last couple days it has been over 1000* and I put a gauge you get when you buy a bottle of freon on it and it is just at or slightly over the green zone and heading into the yellow zone. (The white zone is for loading and unloading only). Any ideas?

 

Cycling of the AC compressor clutch is normal, but short cycling as you describe is usually caused by a low refrigerant charge. You need to put a manifold guage set on the high and low pressure ports and see what the pressures are. Normal low-side pressure averages ~35psi with the clutch cycling between ~27psi and ~47psi. High side pressure should be around 200psi.
The measurements are made with the engine at fast idle, around 1000rpm, MaxAC, max cool, medium blower speed. .....or:

You could take your can of R134A (not Freon) and that adapter/hose/guage and, with the engine running and AC on as indicated above, just begin injecting the R134A until the clutch cycling slows down and the discharge air temp at the registers cools to about 50F.