A/C keeps blowing my blower fuse
 

Okay, this one is very odd. I have a 1989 964. And about half the times I turn on my A/C, it instantly blows the fuse (i.e. fuse #1) for my blower motor. Half the time it works just fine. Very odd. And I'm running out of spare fuses !!

I can crank up the blower myself using the fan speed switch and it never blows. But when I hit the A/C button, look out !! So is there a way to disconnect the blower from the A/C? I can handle controlling the speed myself using the regular speed switch. I don't need the A/C to do it for me - especially if it blows the fuse.

And is this a common 964 problem? Any obvious areas to look at to diagnose the underling problem?