we have a d9t dozer that the ac works sometimes and will freeze you out then sometimes it will stop, when it does if your just idleing it will blow somewhat cool but when you rev the engine back up it will turn hot in about 15 to 20 seconds and be hot like the heater is on. then next time may work just fine. cat has came out and put new thermosatat switch in and both pressure switchs.
Is it freezing up due to poor air flow through the evaporator core.
I will agree on the freezing up. Had a Komatsu that would do that. Never could get it fixed. Just learned to adjust the air when it would start to get warm in cab.
Check the condensation drain line. It may be clogged up as well and causing the evaporator to freeze up.