Ac clutch not engaging

put a paper clip in the ac low pressure switch plug. if theres a little freon in the system. it should click on. if it leaked out then it wont. best to put a set of gauges on it.

 

If the electrical is working. The compressor will kick on. Without freon. Not a good idea to use a paper clip unless you merely touch the terminals only. You can use a piece of wire also. Shoving a paperclip in to the tiny terminals will stretch them out and cause a poor connection on the switch.

Yep. I've done that.

Put gauges on the system and see how much freon is in there. The low pressure switch needs 50 psi to kick the compressor on. Shuts off if it drops to 20.

 

Put a socket on the bolt in center of comp. clutch and turn it a few times around to besure its not locked up , then ck. snowwy pressure test, if it has pressure in system start by cleaning all all push on conn. that are on the a/c lines

 

Being an older truck and what I'll assume is an older compressor, the compressor clutch might need to be reshimmed because it has too much gap to engage. With the truck running and ac turned on, give the clutch a couple little smacks with a wrench and see if it kicks on. If not, put a set of guages on it and see if there's enough freon in the system. As said above you can also test the system by jumping the low pressure switch. Jumping the switch will tell you if the compressor is good, just low on freon.

Plenty of videos on youtube explaining how automotive ac systems work.

 

Had same problem Replace press switch Cost not much, and add freon probely needs freon.

 

When you turn the A/C on with settings inside truck,
Does the engine fan come on?

 

1st in diagnosing ac.

Check pressure.

Most times. Freon is the problem. Not enough or too much and the compressor won't run.

 

Also check the thermostat. Believe me