A/C Questions
 

1987 944
previous owner said he converted the a/c from freon.
when i start the car the light on the a/c switch comes on for a minute or two and then goes out
now that its over 100 here in vegas, i want the air to work as well as possible.
when im driving and hit the snowflake switch, the light doesnt stay on and the air blows hot.
a mechanic told me that if all the lines werent changed that the new gas probably leaked out and i need a charge.
any ideas?
thanks

If the refrigerant gets really low the compressor wont kick in. An AC shop would but some colored dye in and look for leaks, and repair from there.

The lines don't have to be changed. But the new freon is a lot smaller particles and leaks easier. Pull a vacuum on the system to see how long it takes to leak down. If it stays a while, you could put the gauges on it and refill it. The key to knowing wheter it's been converted is the hose fittings are suppose to be changed to match the new style hoses.

Change both the high and low side service port schrader valves, vacuum and then charge it up with just under 2lbs of 134, add maybe an oz of oil for good measure. The front seal is also a common leaker so look there. Black oily residue=leak found.