windows problem on my 91 240

My '91 240 has developed an annoying problem with the electric
windows. That being that they have stopped working most of the time.
I've not had time (working 80 hr weeks for a change) to really look at
them. What is happening is that they only work intermittently and the
time they seem to work is when it has rained. Today I had to run an
errand (and it's raining hard here) and without thinking I rolled the
drivers side window down and then turned the car off. When I jumped
back into the car the window was down and I had a wet ride home. I
would think it was just the drivers side switch but what ever the
problem is is affecting all the windows. Ideas? And thanks in
advance.

 

First thing I would check is the fuse box, corrosion in there can cause
electrical gremlins and is fairly common, especially if the windshield
has ever leaked.