I have a 89 max that is pretty well stock. When I first purchased the car back 2 years ago I noticed that the A/c would kick off if I set the fan to "4". The light on the a/c button would turn off and everything. Set the fan to "3" and problem solved, a/c kicks back on. I didn't really worry about it.
Problem is, recently the a/c kicks off on "3" as well and some rare occasions on "2". Set the fan to a lower speed to a lower speed and it work. Weird.
So anybody got any ideas what the heck is wrong? Is it the climate control head unit? Or something else?

 

I'm not familiar with the non-auto controls, since I have auto climate controls in my '94. Does the A/C button simply turn it on and off, or is it some sort of 'auto' mode, where the A/C will kick on and off as needed?

 

I'd try a new control unit. Might also possibly be the max cold relay by the stereo. It's black and purple.

 

It sounds like the same behavior the old control unit of my Max did. When I had it at 4 the AC would not kick in until I jiggle the level so it can kick in. Must have been a bad contact.

I changed the control unit and problem solved.

 

sounds wierd they are probaly designed to turn off at WOT maybe if so
you have sensor problem etc.