I would think the problem is in the wiper switch not the motor. There is also a delay assy on the firewall under the dash. So it would be the the turn signal stick oor the delay box. The motor just does what it is told by the other parts. The speeds change by resistance before the wiper motor.
89YJ 2.5L TBI, AX-5, NP231 SYE, Ford 8.8, Yukon Grizzly, Tom Woods Shaft, 33" BFG T/As, 4" lift, Warn VR10000s.
AF Jeep Club Tail #184