Without serier number hard to tell but if older model l would open covers on steering column and look at switches some had four switches two in center and two on each end one is forward and one reverse check to see when in gear that switch is working sometimes switch gets worn and does not make contact with arm also l have seen wiring coming off switch if checks out go to coils on top of trans one is forward and one reverse normally both have common ground when in gear forward should get positive from switch and when in reverse should get the same.the two in center switches are natural for starter