Intermittent AC (and heat) failure in '93 88

This car has about 100K miles on it. For the past year, maybe once every three or four months, without apparent cause (e.g. not particularly hot or cold weather), the whole HVAC system just quits. It never happens when the car is running; only when I start it up. I have the automatic climate control, and its display looks perfectly normal: The temperature can be dialed, the fan switch can be "run" up or down, the AC and defrost symbols appear; but nothing happens! That is, no air comes out at all, neither hot, nor cold, not even vent. This may last for a day or two, and then come back to working perfectly, as it did over the weekend.
My car mechanic says he can put a new climate control "computer" in, but the part alone is $600!! Can anyone suggest at least something else we could investigate, before this major expenditure that might not even repair the problem?
Thanks,
Beach004

Since no one seems intrigued by that approach: Could it be that what I am experiencing is not failure of the computer, but failure of the fan? When this intermittent problem occurs, no air at all comes out of the vents, even at highway speeds; but I believe in some cars this can happen--that is, no air flow without the fan.
Obviously, I would rather work on the fan switch replacement than the computer module, from a cost standpoint. Anyone have experience with the fan cutting out? Unfortunately, the problem has once more gone away on its own; but I feel sure it will be back--probably on a 95 degree day...

I have the same problem without it being intermittent. I am hoping that the blower motor is a fault here. The fuses are fine but I am not sure about the correct relays to check. I am not a complete novice but electrical is a weak area. H E L P !!

I have the same problem as you, all the fuses are fine, I have checked the relays, and replaced the blower motor and still nothing. Now the I have changed the blower motor, I can hear the motor running, so I know that the motor is getting power. It almost seems as though it may be blocked. Check to see if you can hear the motor spinning in the background.