There is now self-refilling a/c out there.. they made new rules, cause people were complaning about changing the whole system costing too much.. you can get the refill kit for not too much like 20 bucks for the hose and 10 bucks per can... its easy to do it.. i did it to my moms BMW, my 944 and a Benz already..

but this only works if not work a/c is just becauase a/c gas running out.

Mine is a piston type. Have no idea of a diaphragm would work or not.

AFJuvat