the only way my wipers work is to activate the switch under the steering colomn while pushing on the wiper button and holding the button down which puts thw wipers in the wash mode I have a good ground and the limit switch is closed!

I also had problems with my wipers on my 1972. After checking for ground and other possible wiring problems, replacing the wiper switch on the dash finally fixed the problem. Often the wiper switch is the cause of most problems. Try this and good luck.

if the switch is not the problem then check for a loose connection at the back of the tach. There is a connection there for the wiper door opening not sure if its a relay or ground etc never seen it but felt it and reconnected it. If this comes loose or not attached then you will have to use the override switch below the steering column then the wiper switch will work normally until you then have to manually close the door with the override switch. Had this happen to me and a few others that I know of.