my ac compressor runs constantly does not cycle. all fuses and relays are good. when i pull the fuse inside the truck the compressor cycles normal. does that mean i have to replace the "control unit" that is in the dash rite below the radio.? 2001 tahoe 5.3 and i have done nothing to the truck.

 

Is it freezing up and airflow the vents dropping of or something that makes you think it's abnormal. Depending on outdoor ambient and temp in the car it may not cycle. If it's freezing up and airflow falling off after an hour or so of steady driving replace the cabin air filter and the clutch cycling switch on the accumulator under the hood.

 

it runs continuis if its 90 degrees or 70 degrees heat on or off . nothing freezes up it works normal just the compressor wont cycle????? i will do what you say to see if it makes a diff.