I have a 2014 Nissan Sentra with A/C not cooling. It gradually lost cooling, my fault for not addressing it sooner. I bought and used a recharge kit but didn't seem to take as I could not get the system to kick in and cycle. I would like some help with the diagnostic process, step by step, so I can eliminate some possibilities such as compressor, clutch etc., and not be taken by bad mechanics. What are the proper costs of the different possible problems I may have. I live in the Austin tx. area and would like any recommendations as to an honest shop to take my car to after I have gone through my own diagnostics. Look forward to your response. Thank you, Tony.
Those "recharge kits" are useless for any kind of diagnostics and may do harm if they contain sealers. To start your diagnosis you need to check your system pressures with a manifold gauge set. If your compressor clutch will not engage you probably have so little refrigerant in the system that pressure has fallen below the threshold where the safety cutoff switch kicks in. (Most will not allow the compressor clutch to operate if low-side pressure drops below about 20 psi.)
What is my next step? Find someone with a manifold gauge set to check the pressures?
If you plan on working on your own air conditioning moving forward you need a manifold gauge set in your tool collection. A set suitable for occasional home use is not very expensive. There are plenty of instructional videos on youtube showing how to use it.
https://www.amazon.com/Orion-Motor-Tech-Conditioning-Maintenance/dp/B08V5JWJSB