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Ok, still no joy on the a/c blower or compressor coming on. All fuses in the fuse block check ok. The cluster of four round relays above the fuse block all click when the ignition is turned to run except one, but swapped it with one next to it since they are the exact same part number, and the relay itself checks ok. Don't know what circuit this third of four relays is for, since my wiring diagrams aren't that accurate. On the passenger side behind the glove box, I've checked the blower motor resistor and all coils show continuity. The blower motor isn't getting power with the switch, but does run when directly jumped. There was one other round relay in the wiring bundle above the glovebox, same part number as the cluster of four above the fuse block, was not clicking when ignition turned on. Again swapped it into a known clicking one, and it does indeed click. As stated before, chased all vacuum lines to and from the selector switches. No leaks, and can hear dampers move when buttons are pushed. The two square relays behind the passenger side strut tower and its fuse check ok. One thing puzzles me though, there is a small circuit board on the pushbutton selectors. Only three wires are connected to it, a solid green, solid yellow, and a solid black. The black one I presume is a ground to the three lights on the selector block. The green one reads 12v with the ignition on and selector off. Yellow reads 0v. When any other button besides off is pressed, the green one goes to 0v, yellow remains at 0v. Is this normal? Is this where my problem is? Don't want to jump these wires for fear of damaging something. Any and all idea will be appreciated. Thanks.

I've checked all the vacuum lines in the system, and all appear intact without loss of vacuum. Still searching for that last stealthy relay. I'm beginning to think it is electrical in nature. The blower works when 12v is directly applied. Going to start chasing wires from the selector switch and fan speed selector knob. The wiring diagrams from the Haynes manual I have are decent, but rather vague since they attempt to cover multiple systems over multiple years. Thanks for the suggestions Stratman and Somick. Open to any and all ideas. Thanks again everyone.

I have a 1988 DL, excellent shape, under 67k miles (really). This car sat for nearly 10 years mostly inside, some outside, and under a carport. It was just started and driven a couple of times a month. Lots of TLC has revived this little gem into my daily driver. Just recently, the R-134 converted A/C compressor and blower cuts out and just stops working while driving. None of the selector buttons or fan speed switchs work. Ocassionally, it will turn itself back on only to stop again the next day. I checked all fuses both under the drivers side dash and the two relays and fuse behind the passenger side strut tower under the hood. All check ok per the Haynes manual I have. I've not pulled the blower resistor block yet because when it does come back on, all fan speeds function. I have disassembled the dash and glove box area and removed the stereo looking for an additional relay that is mentioned in my Haynes manual, but can not locate it. Other than this invisible relay, I'm running out of ideas. Anyone had similiar problems? Could it be the selector button switches? I hear the vacuum system moving duct levers when the buttons are pressed. Is this something simple that I am overlooking or over analyzing? Any and all suggestions will be greatly appreciated. Thanks.