AC issues

Hey everyone, I have some AC issues and wanted some advice.

Over the past few months my AC has been becoming weaker until a couple days ago it quit blowing cold air altogether and the AC light started flashing. It blows air but it’s just not cold.

From previous threads I was able to determine the AC fuse and the magnetic clutch rely are both good. I used AC manifold gauges from auto zone and found that both the high pressure and low pressure lines are reading the same at 60 psi. I also noticed the compressor clutch isn’t engaged when the AC is on and you can spin it manually with a small amount of force when the truck is off. When I turn the AC on there aren’t any noises coming from the compressor and I didn’t notice any in the months leading up to it stopping completely. Was wondering if it sounds like a bad compressor clutch or a bad compressor and the next steps I should take.

 

The flashing A/C light is when the A/C amplifier does not detect a speed signal from the compressor lock sensor after commanding the MG CLT relay on.

Possible causes are:
Open or shorted wire(s) in the lock sensor circuit
Bad lock sensor
Internal problem in the compressor
Open or shorted wire(s) to the MG CLT relay
Open in the wire from the MG CLT relay to the compressor
Failed compressor clutch
Belt slipping
Failed A/C amplifier


Does the A/C Compressor turn on for a few seconds and then turn off when you press the A/C button or does it not turn on at all?

 

Thanks for the response,

The engine revs up but I don’t hear the compressor turning on at all and the AC light starts blinking pretty much as soon as I turn it on. I ordered a power probe to test the magnetic clutch which is what is next on my to-do list.

 

Do you have a test light?

If so we can narrow this down pretty quick, test light connected to battery Ground check for power on Pin 2 & 5 of the MG CLT Relay with the key on.
Then test light connected to battery Positive check Pin 3, it should light up if the wire is continuous to the clutch coil and the coil windings are good.

If that all tests good then with the light still connected to battery Positive start the truck and have an assistant hit the A/C button while you hold the light on Pin 1 of the MG CLT Relay, it should light up briefly until the light starts flashing.

 

I don’t have a light test but I’ll get one and try this out.