Wiper Motor?
 

When useing my wipers they will occasionally stop.. sometimes starting right back up and other times not. I can get out and move the arms and it'll catch and they'll run fine for a while. Also their speed varies from real slow to normal speed.
Also, with my wiper switch off and motor not running... if I move the windshield wiper arms... it'll cause the dome light to dim down... like it does when you initially add a pull on it... why with the switch off and just moving the arms????

There is a cam on the motor drive that electrical contacts ride on. That's what turns the motor off when wiper arms are in the down position. Sounds like it is malfunctioning, shorting out when you move the arms, therefore the dome light dims. As to speed it could be a problem with the cam as well. My memory fails me as to how the contacts (brushes) are setup on the cam. Replace the wiper motor and the problem should be gone.
Larry
68 C20 327/465 daily driver 4:56 och!
63 C20 292/420 Camper truck Detroit Locker 4:10 posi
65 C10 ? /powerglide Custom Cab AC,PB,PS,4xflasher