I own a 580SE that had a previous engine overhaul and new transmission. There's a few issues I need to resolve but the machine feels basically "solid". Here's the latest issue; This winter it was starting fine when suddenly I could not get it to crank when turning the key. I could easily get it to start by jumping it at the starter so I have been starting it each time that way. I've now decided I need to get the problem identified and fixed. I've searched and read messages relating to this problem. I found the Neutral Switch and disconnected the harness. I placed a jumper wire on the wire harness and nothing changed. I was disappointed and surprised. So this morning at 4:00, I could stand it no more and got up to check a couple of things. I placed a 12 volt test light on the machine. I clipped the ground wire to the ground stud on the starter. I was going to check and see if I had power in the wiring harness when I turned the key. WITH THE KEY TURNED OFF, I was surprised to have full power to one of the wires in this harness. Turning the key to START changed nothing. I then switched the test light to the other wire in this same harness. There was no power with the key to off position. When I turned the key to start, the engine cranked and started. I was surprised as the test light never did light with it in this position. I turned the key off and repeated the sequence several times. Each time I had the same result. When the test light was present, it completed a ground circuit to that harness and everything works fine. When I returned the harness to the Neutral Switch, It quit working again. I do have power to the gauges and I can barely hear a clinking sound in the dash area when I try to start it. I'm not sure what to do next. I could just ground that wire and things would start fine but it would override the Neutral Switch. For safely reasons, I don't want to do that. What do you suggest? I didn't think that harness would have any ground function in it. I was also surprised to have full power in that same harness (other wire of the pair) when the key was in the Off position. What do you think? I appreciate the great advice and knowledge of those on this Board.
two different neutral start systems They used two types, one had the wire from the starter hot lug to the 40 amp breaker, from the breaker it went to a connection to the next harness. It traveled to the key switch, when turning the key it sent current to the magnetic switch in the dash, back down thru the harness connection, to the neutral start switch, then on to the starter small lug which started your machine. The other, from the starter hot lug to the 40 amp breaker, from the breaker it went to a connection to the next harness, it traveled to the key switch and also to a relay. From a different lug on the key switch a second wire ran to another relay lug. Another lug on the relay ran to the neutral start switch, then to ground. There is a 4th lug on the relay that went back to the connection on the harness, thru the connection and back to the small lug on the starter. I would check all grounds, battery box to frame, to engine, to cab area. You may have to remove the four screws holding the dash in, slide the dash back and press the tab to release the tach cable to move the dash cluster out of your way, it's a little tight in there. If you have a multi meter with a toner it helps to find and trace quickly also.