A/C Problem?
 

My car: 1988 BMW 325 Coupe

My problem: On the highway with A/C on with fan level at 3 (levels are 0,1,2,3,4). I switch to 4 and then it just stops and cuts off, not jsut A/C, but all air from vent. Nothing works now, no air, no heat, nadda.

Any help someone could give me that might be the problem?

sounds like a bad fan switch, or blower motor (ie the fan that pushes the heated or cooled air through the vents) just died. good luck, both these can be a bear to replace.

any chance it could be a blown fuse?

Well, it was a blown fuse indeed. Melted the plastic to the fuse box as well. But at least it isn't something more expensive (fan, blower)

Many cars have a separate high blower relay to control the extra amperage draw, or control blower speed through a series of resistor coils. Failure in either one might cause you to have lower speed blowers, but not maximum.

If you have no blower at all now, check for power at the blower motor. This can be done with a simple test light ($5 or $6 at any auto or hardware store). Power there = bad blower motor. No power? Repeat the test at the switch. No power through switch = bad switch. Power through switch? Locate the relay. It's probably your problem. You have just saved yourself $60 - $100.