[Jim3inVirginia]

When I took automotive HVAC class at the local community college I was impressed to learn that systems are charged based on quantity of the refrigerant by weight, rather than system pressure as implied by all the DIY cans of refrigerant commercially available. I had my '95 properly serviced back in 2016 at a local auto a/c shop that I like. When the performance was weak in 2019 I added a can and its been nice and cold since. A/C service was always one of those things I left to the pros and still do for newer vehicles with less tolerance for discrepancy like my wife's Fusion or my new F150. But on the ol' T-bird I try DIY first and then hire a pro if needed. Other advice I gathered from HVAC class: never buy DIY cans with sealer, that messes up the system. Good luck with the a/c in the '97.

 

[Jim3inVirginia]

Did the can get cold, did the metal lines going through the firewall get cold? Despite directions on some cans that say hold it upright I've found that upside down, move it around, shake it, helps. Center outlet air temp on high/recirc on a properly working system should be 45-50 degrees. It does better with the car moving and air is flowing through the condenser. If its nowhere close to 50 and the compressor is clutching or clutched and the system won't take more refrigerant then it could be a restriction in the system.

 

[Jim3inVirginia]

Just to verify: when you used the can, you saw pressure increases each time you checked the pressure after each cycle of adding refrigerant?

Sorry, I wasn't focused on the pressure, just noticed that it went up and down as the compressor cycled on and off (or off and on). According to my notes I only added one can. I imagine if I added one can and it helped a little I would add another can. But: I wonder about the compressor running continuously. I'm no expert but I expect it would either not be running or cycling rather than running continuously.