Good evening. I have quite the conundrum on my hands. I've had this problem in the past, but I believe the starter on my LS 160 just burned up again. Here's the history. About 1 year ago the starter would just burn up and I mean smoke, catch fire etc. It was dramatic, and it would happen out of the blue when the machine was running. No cranking whatsoever. After some trouble shooting, I deduced that the interlock relay was getting stuck in the closed position. It was hard to find as it was an intermittent problem. Machine failed to turn over today after running it for a bit. Everything seems to be in order, strong battery, seat belt switch working properly, glow plug light turning off quickly (i'm in a warm state). I felt the starter and it was hot despite not being turned over once. You'd think with power going to the starter solenoid there would be some cranking or grinding etc, but none of that occurred. I've attached a diagram of the starting circuit for reference. To have this happen again is so frustrating and I really just can't wrap my mind around a starter burning up when it is not cranking. Is it possible that the starter is just free spinning without engaging the flywheel? The main issue I have is how do I protect the starter against another failed interlock relay? Should I fuse between the interlock relay and starter relay? I was also thinking about ditching the proprietary interlock relay and splitting it into two bosch mini relays. It seems the only real benefit of the interlock relay is that it saves a little space.
If you didn't care about the seat safety switch you could delete the interlock relay from the start circuit and just run a wire from either the ignition switch or the service run switch. This would eliminate the chance of a stuck relay engaging the starter as there would be no power unless the ignition switch itself malfunctioned and provided power. You could also add a normally clossed oil pressure switch into the wire between the interlock relay and the start relay or if the amperage is not to much between the start relay and the starter solenoid. This way when the engine is running with oil pressure the switch will open and not allow power to the starter.
Thanks for the reply. I was thinking about it and wouldn't a NC oil pressure sensor not allow me to start it? Regardless I'd like to keep the safety features in there. Today I was troubleshooting the machine and I wasn't able to jump the starter. All the other relays in the starter circuit checked out, which isn't surprising as a stuck relay can be very intermittent. While crude, i'm thinking of just adding a switch to the starter solenoid wire that would have to be manually turned on before starting and off after starting. I can't thinking of any other way to protect the circuit assuming the relay gets stuck closed with normal amperage running through it.
A normally closed switched means its "ON'" without actuation, so without oil pressure it will allow the starter to operate. you could add a push button switch to do the same thing as the oil pressure switch. instead of thinking of it as crude think of it as "anti theft"! chances of someone holding a push button while also turning the key is slim to none.