The first $$$Costly behavior!

In hot summer weather, typical of Southern Oregon, the A/C will not function. I try to go to all buttons on the console as well as move the temp.wheel to and fro. The a/c will not kick in.
After car has been turned off and restarted the a/c will work if the a/c buttons have been selected and the temp.wheel is in 65° or less setting.

To fix our dealer took $750 to replace several switches and filters etc.!

The problem is not solved if I switch from a/c to economy or off with engine running. Sometimes a/c is not needed even here!
It was suggested that I allow more time after switching back and forth.
It was suggested that I not switch at all when it is working?

Any thoughts would be appreciated.
Answers please?

Please let us know exactly what the dealer replaced. This sounds to me like a bad circuit board in the A/C control unit, but I want to make sure that the dealer didn't already replace befor eoffering suggestions.

Troy
1995 E420
83k

OK, here is the parts replaced list:

140-830-04-84 Expansion Valve
124-830-03-83 Container
004-820-68-10 Switch, Liqui
124-820-83-10 Switch, Recei
140-997-09*-45 Seal Ring, VL in OR (3 additional seal rings: (*08-07-06)
124-830-01-18 Air Filter

That parts list amounts to $296.00

Tech(s): 123 171

Any thoughts?