1997 Bravada, all works well, then without warning or reason, a/c goes off, fan goes off, windows will not operate, ABS light comes on, the compass works but the outside temp does not. Sometimes comes back on in a minute, or ten, today not for hours. Naturally when we take it to mechanic it works fine. One mechanic wanted to just start replacing stuff, this over here, that over there, maybe it will work, or not. Help! any suggestions??? Also on occassion the temperature gauge will climb to overheated, check guage light comes on, then just as quick all will return to normal.

 

It sounds like you may be experiencing the beginning of an ignition switch failure. The circuit can be tested relatively easily, however, if it is working, it may test fine. Ignition switches tend to be on again, off again for a bit before finally dying for good.