AC is AC.........Caterpillar backhoe

[tompands]

I have a Cat backhoe I bought and AC wasn't working. The guy gave me $1000 off the price we agreed on. Started checking it and found the condenser had a leak. Changed the condenser out. DIDN'T change accumulator. VERY hard to get to and figured I might get lucky and it will work. Yeah, NO! I charged the system with 3lbs of r134 and its still not working. Blowing hot air. Pressures are 120low/130high. And not moving. I don't know if the compressor is bad and not compressing or what it could be. I know I should have changed the accumulator/drier, but I didn't. Any thoughts???

[tompands]

Also, I did a real good vacuum before I charged it.

[bohica2xo]

First step with those pressures is to look at the drive end of the compressor and make sure the hub in the center is spinning, not just the belt pulley

Come back with that information and we can go from there.

.

[DetroitAC]

Compressor isn't turning, check clutch relay, clutch wires, clutch coil, coil ground. Maybe Cat disables the clutch relay permanently if you lose charge, and you need to pay the Cat dealer to turn it back on?

[JohnHere]

Have you measured the clutch gap and/or tried nudging the front of the clutch with a suitable wood tool, like a section of 2x2, to see whether it engages? The clutch gap might be too wide for the clutch coil to pull-in the driven disk, or the coil itself might be defective in some way as mentioned. However, the static pressures sound like there's plenty of refrigerant in the system for the clutch to engage.

Although difficult, you should have replaced the accumulator because the desiccant might be saturated.

Some additional questions: Did you remove the OT to see whether it had any debris on it? Did you evacuate it down to at least 29 InHg, and for how long? Did you then recharge it to the Caterpillar specs? What year is your Cat?

[bohica2xo]

Saying CAT backhoe is like saying "Chevrolet truck" It could have many different systems.

I have found GM V5 / V7 variable displacement compressors on Excavators. Safe to say it could be a few things causing nearly equal pressures on this system.

Compressor shaft not turning. Could be a bad clutch, electrical problem or PCM lockout.

Compressor shaft turning. Could be a bunch of broken reed valves. Failed control valve. Shaft sheared at the swash plate.

Clearly need more information on the equipment.