I replaced the brake interlock switch yesterday and the truck operated normally. The customer phoned me this afternoon and tells me that it is acting up again. Travel still returns to normal operation after stepping on the brake pedal and cycling the directional lever to neutral. I'll return tomorrow morning to check the switch adjustment and card inputs... any ideas would be welcome.

DennisM, the brake interlock switch appears to be an original. I have one on order and will update this thread with the results after I have observed the truck's operation with the new switch for a while. Thanks for the heads up.

Brake switch makes sense too... I'll look at that as well.

I have thought the same thing as well. The seat is an aftermarket Grammer B12 with that unusual swing arm OPS actuator. See video: https://www.youtube.com/watch?v=IuxpLL17xrc. Most recently the operator tells me that he places the directional selector back in neutral and steps on the brake pedal (which may change his position on the seat). After that he places the directional selector in forward or reverse and it begins working again. Trouble is... I have attempted this many times without the same results. You can manually operate the switch and hear the steer pump motor spool up although travel is still inoperative. Cycling the key does not seem to make a difference either. I am going to visit this customer tomorrow and spend some more time on it. Seat, switch and wiring have good integrity. Nevertheless I will be looking at them again closely.

Brake switch, pedal holding on.

If it is doing it only when getting off truck,i would revisit the seat switch and wiring and such sounds like problem is there......what does the operator have to do to get it foing again when it does act up????