I guess my long streak of no problems has come to a screaming halt. AC wasn't working. Took er in to have it checked out. Dude did not find any leaks under the hood but suspects evaporator (OEM) maybe leaking. He charged the system up but did not know how long it will stay that way. I replaced everything AC related under the hood about 4 years ago so that leaves the evaporator as the last part being OEM. I see that replacing one in a Bonny is a pretty big job. BUT, just maybe its not so involved in a 88? Evaporator isnt much money (relative I guess). What am I looking at here to R&R the evaporator in a 88?

STOP.....in the name of love....or all that'* holy......

Don't just assume it'* the evaporator, just because you didn't find the leak.....you don't say how long it took for the refrigerant to cause a low pressure problem.....could be a small leak that you have not found....

Would recommend a dye and black light, before you pull that dash apart....

I think you have to pull that one out from the engine bay if I remember correctly, but I could be wrong.

I agree, UV dye, blacklight. Also a clean engine bay goes a long way too. Evaporator really is an absolute last ditch option.

You can also usually pull the resistor pack out, and get a look at a good portion of the evaporator with a black light.

I have the same situation with my '95 Aurora. I can charge the system up and it'll leak down in about a week or ten days but the system will hold vacuum.

Seals or leaks behave differently under a vacuum vs being under pressure. That'* why we have to use nitrogen to "charge" the system to test for leaks without using expensive freon.

Human, something leaking that fast, should easily be found with a dye and black light.......

Could it be the seals in the compressor? My '93 once leaked out all my original R-12 charge through a leaky compressor seal. I recharged it with new R-134a with stop leak and it hasn't lost the charge since. Also, check the schrader valve on the high and low side of the system.