A/C on/off switch fix?
 

First the defrost switch and then the a/c on/off have recently failed to "lock in". Both still function if held. Is there a fix, or do I buy a whole new used unit, or can I cowboy something with a piggybacked switch for the a/c compressor somewhere?

I'm more or less a 911 guy, so forgive me if this is common and I didn't find it with a search....

The aircon on/off switch also controls the thermostat on/off. The thermostat is a thin tube filled with what looks like alcohol. My tube broke, and I replaced it with a cheap aftermarket item, connected the two wires and installed a seperate switch. My aircon clutch only engages now if I "swith on" the thermostat. The big knob that controls the fan and that used to control the thermostat now only controls the fan (two settings).
When you gas is low, your aircon will also not engage.

The issue here appears to be mechanical within the switch-you push it in and it doesn't "lock" in place, altho it works electrically and energizes the system.

it gets pretty common with 20 year old cars. There are two types of a/c control units, with and without replaceble switches. If you have the replacable one, you can purchase new switches and pop them in. If not, I taken the fixed switches apart and replaced the small plastic part that wears with ones from other dead units.