On my 1968 Olds 98 convt, I still have the A/C with the original freon. The mechanic recharged it back in July 2022, charged me $70/lb. However yesterday when driving in the 90 deg heat, I found the A/C was not blowing cool air. Is there a way a mechanic can find where the leak is. If one has to convert the A/C to the new freon, what all needs to be replaced besides the A/C compressor?

Picture of the A/C

 

The only part that needs to be replaced is the drier. And whatever is causing the leak (o-ring, evaporator, etc).

 

Make sure the compressor clutch is engaged and running.

These cars use a compressor clutch hold-in relay mounted on passenger side fenderwell. If it fails the compressor won't engage. There's also a compressor switch on the HVAC control panel.

If compressor is engaging then you need to put pressure gages on the system and see what system pressures are doing.

If it turns out the refrigerant charge is low, a shop that does much air conditioning work will have the tools and the talent to find a leak and repair it. There are electronic leak detectors, propane torch type detectors (those let you know where the leak is in a hurry!) and a few others.

Keep in mind when these systems were new, loss of a pound of refrigerant per year was considered normal and acceptable. That was before guilt-ridden neeners who don't understand refrigeration machinery and how it works entered the picture.

Always amazed me they went after mobile CFC based refrigerants but ignored stationary ammonia refrigeration systems. Ammonia is a way worse hazard than any CFC. But, ammonia systems are stationary, mostly used in ice plants and cold storage facilities. Not in cars.

What does that tell you the real goal was?