I have a 94 & 96 1500 Chevy each had the same winshield wipper problem. I removed the control board and found the same problem on each board, the solder joints to the relay and delay were bad i resoldered those joints and have had no more problems.
heads up Intermetant wiper problem on 1996 Chevrolet 1500 Pickup
This is a very common problem for GM truck for quite a number of years. If you "tap" lightly on the wiper motor cover and the wipers start working, you have found you problem. Some vehicles were recalled for this problem and some were not. You will need to check with your local dealer to find out if a specific vehicle was included. This problem has been reported by RepairPal - http://repairpal.com/chevrolet-1500_pickup-1994/problems
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you can take the panel off the wiper motor and there is a circuit board behind it. If you remove the circuit board, look for cracks in the board. You might need a magnifiing glass.Thats what happened to mine and i soidered them. It worked fine after that.