a/c starts and blows cold. in 5 to 15 seconds the blower stops. turn rotate switch to off position. wait a couple of seconds ----- turn on a/c and the air blows cold for a few more seconds once again. then just stops. repeat over and over with no differences except time of operation changes
Have your trucks A/C system diagnosed and repaired by an A/C repair specialist
Is it the blower motor that stops? Does it stop on all speeds? Does it stop blowing whether AC, vent, heat, or defrost? Then I would guess the something is wrong with the blower motor itself. But if you can check the voltage going to the motor when it stops. If power is going to the blower then, to me, that would mean replacing the blower motor.