I have a 2007 Ram 1500….think the compressor is fried. Plenty of Freon but compressor won’t spin. Shows plenty of Freon.

 

Could be as simple as a bad pressure switch....

 

So how can I diagnose it

 

Got a volt meter? Follow the compressor circuit, and see where power goes away. Wiring diagrams are pretty much a requirement here.....

 

You have no way of knowing how much refrigerant it has unless you recover it into a bottle and weigh it.

 

"Compressor won't spin".... So the clutch is not engaging? Have you checked the compressor fuse or tried swapping the relay?

 

Can you turn the compressor by hand? (With the engine off of course.) If the compressor will turn (grab the clutch on the front) it's okay. Then your switches might be bad. There will be one or two. One on the receiver/dryer and maybe a cycling pressure switch on the line near the compressor. Get some mechanics wire. and unplug the connector on the dryer assembly. (Looks like a black coffee can on the passenger side of the firewall.) Stick the wire into the two holes where the switch goes. If the system begins working, you either have low pressure or a bad switch.

To check the amount of refrigerant, you really need a manifold set for R-134. My gut feeling. (Why yes, it IS a rather large feeling) is your refrigerant is just low enough the compressor switches have kicked it out so you don't grenade the compressor. Your truck is 16 years old and R-134 does seep out over time. So, your course of action can be to grab the compressor and make sure it isn't locked up. Then head over to the auto parts store and get a recharge kit. There are some that hook onto the low pressure port on your a/c system. They have a gauge and trigger. Get everything hooked back up (switches and stuff) and start the truck and turn the a/c on. Snap the charge kit onto the low pressure port and pull the trigger. Your system should engage when the pressure comes up. Watch the gauge and keep it in the blue and out of the red.