2005 Peterbilt AC problems

I assume you mean compressor? What model are we working on? First make sure system charge is full to the proper refrigerant amount. Next stop is to check your low and high side switches to see if they are both closed when they are supposed to be. Compressor cycle switches are a common failure item. Make sure you match the color to the correct location and dont get them mixed up.

 

When Your AC doesn't work it is either;
#1 Insufficient Freon
#2 Electrical Issue
#3 Mechanical Issue

First, make sure there is freon... Hook up R134a gauge kit to check freon level. Without compressor running, it should be at about 90 psi.

If that's good...
Check the Electrical side of the system.
Put 12v at the compressor to check the compressor clutch.
If good, you can bypass pressure switches by using a paper clip to hardwire at the connectors. Do one at a time to determine which switch is bad. (When pressure switches are hardwired you'll need to watch your pressures closely. Don't go under 10psi on the low side or 375psi on the high side.)

If you have both power and ground at Compressor but the clutch doesn't engage, you'll need a new AC compressor clutch.

Good Luck!