I have a JLG 40H that the ground control for lift and swing quit working. It seemed to work intermittent just before it quit altogether. All controls still work from basket. when I try ground controls the amp gauge drops a little bit so it acts like it drawing amps. any idea where to start.
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From what you're describing, everything works at the lower controls except boom lift and swing, problem is most likely with the resistor that feeds power to the boom lift and swing toggle switches. There should be a red wire that comes from the start button and goes to one of the center terminals of the lift toggle, then it jumps off and goes to the swing toggle. Between the start button and the lift toggle that wire should have a 7.5 Ohm resistor inline, check your voltage in and out of that resistor.