My thanks for your replies... I definitely want to stay with the r12 for now... less hassle, less expensive, less work, etc. That's assuming I can run down the source of the leak. And no, I would not put any stop leak product in any of my cars... that's like using proto-matter in your Genesis Device...

Greetings all, I recently bought a 1991 Mercedes 300D that is still running r12. Seller said the ac had been week for a couple years but he never felt the need to repair or switch over to r134a as it was a weekend driver. Compressor clutch won't engage. That tells me there's insufficient refrigerant...