The wiper sled on our '71 convertible stays in the up (open) position all the time. It isn't physically jammed, because I can manually force it closed. When I do, it slowly comes back up again. Do we have a bad vacuum motor? Some other vacuum problem?

On the edge of the lower dash under the steering column there should be a round knob flanked by two stalk switches. All three switches are documented in the owners manual.

The center knob is an electrical cut-off for the wiper motor, the left stalk is an override for popping up the headlights, and the right stalk is an override for opening the wiper door.

'Normal' position for the stalks is pushed straight up. When pulled straight down the left stalk will pop the headlight doors up without turning on the headlights and the right stalk will raise the wiper door without turning on the wipers.

My hunch is that the right stalk is pulled down and the center knob is cutting out the wipers from operating. If the right stalk is pushed up already, pull it down and see what happens. If the wiper door goes down I would check the routing of the vacuum lines as they might be flip-flopped. If the door doesn't move with the stalk in either position you do have a vacuum issue of some sort to figure out.

btw - have the engine running to produce some vacuum or hook in an external vacuum source to check it out.

Explaination prevoiusly given was excellent. If that doesn't solve problem do a search online for Corvette Vacuum and read up on the system. Understand the system and you can isolate where the problem lies. You can also buy some trouble shooting guides from Dr Rebuild that are very helpful.

Vaccum problems have driven many a Corvette enthusiast crazy but they can be solved.