1999 GMC K-1500 4x4
 

My A/C won't cycle I was told it was low on refrigerate, I also have rear air on this unit. I installed (5) cans and nothing I check all connections for power all relays check out, confused on what could be wrong? Clutch will in-gage by jumping power to it. won't cycle otherwise. any idea's? Question whats it's capacity? Help its getting hot in here. ROD

I would start by checking the low pressure switch on the accumulator.