A/C unit

by kickin on im assuming ur talkin about the clutch on the compressor, its supposed to do that even if ur truck had the a/c turned off to circulate the refridgerent, u could have a leak in the system thats the usual cause of "not cooling" try a quick seal kit and a couple cans of recharge, if that doesnt solve the issue, it will require further diag as to y the system is not operating

i would drain the system and then shot dye in the system and refill it and wait a week and get a black light and look and see if you have a leak

You might need a new ac compressor.