1988 Buick Regal left window switch

The window switch should have two wires running to it. One wire will have power to it when the switch is held in the UP position and the other will have power when the switch is held in the DOWn position. If that's the case, check to see if power gets to the window motor (you'll have to remove the door panel first).
If power gets to the window motor and it still does not operate, the window motor in bad.

NOTE:
The actual power window switch assembly on the drivers' side will have more than two wires in the plugging into it; however only two will operate the drivers' window. You may have to attach to DVOM leads to a wire, operate each switch until it shows power in order to determine which wire is controlled by which switch, until you have the wires which operate the drivers' side narrowed down.