AC issue

So I turned on my ac for the first time this year and the compressor doesnt engage.
- compressor spins freely
- ac light comes on like it should
- I changed the mag clutch relay and fuse
- I DID recently have the control module out while changing my head unit but I have visually inspected the harness and pins and all looks ok.

Any suggestions before I give up and take it in to a trusted mechanic?

 

Are you sure the compressor is spinning? The pulley around the compressor may be spinning, but the compressor shaft may not be. Can you take a closer look? If you are low on refrigerant. The compressor will not engage, but the pulley will be spinning freely.

 

Sorry, I meant the compressor spins freely with the truck off. The clutch isn't turning on. I have previously replaced the clutch.

 

If your refrigerant is low the magnetic clutch will not turn on because of a low pressure safety switch. You must connect a guage to see what pressure you have in the system to get an idea of how low it might be. That would be the first thing to check.

AC compressor all leak just a bit because of how the front shaft seal works, so the system has to be topped off sometimes. I lost 6oz of refrigerant in 5 years from a new compressor, and the whole system takes 24 oz.

 

Take a good look at the rubber on the clutch, its common for it to separate and wont allow it to engage. the rubber will just spin with the pulley but it will actually rotate the center shaft. You can also try grabbing the front of it pull on it to see if the rubber is seperating.

 

I had that problem in the past and replaced the clutch. It looks good. When that was going on the ac light would blink and the turn off. It stays on solid right now.

 

I'm going to take it in and get the pressure checked

 

If you can spin the compressor not the clutch it means you have zero pressure in the system or the shaft in the compressor snapped.

In either case it is going to be expensive .

 

We will see I guess.

 

Jumper the pressure switch contact out and see if the compressor engages (only do this for a moment, you will damage the compressor for long term operation at low pressure). If that's the case, you either have a bad pressure switch or low refrigerant. If it doesn't engage with the pressure switch jumpered, you have a bad A/C amplifier, A/C relay, or possibly the air gap is too large on the clutch. You can pull the relay and check that, and can pull the connector to the compressor and check for voltage there when engaging.

 

Turned out to be a very small leak in a hose resulting in low pressure. $33 aftermarket hose replacement and a recharge.