Bjohnsonmn Posted January 25 Share Posted January 25 (edited) Funny that this post is following an post called "Engine won't start". 2000 Windsor 32PB, House and Chassis 12v systems fully isolated (LiFePO4 house swap) As is the case for many of us, my DUVAC Lacee alternator generated its final amp and died in rather remarkable fashion. When I pulled it from the engine, the positive post pulled out of the alternator. It had somehow been acting like a foundry and was melting the various metals surrounding the stud in the alternator into some kind of new metal that surrounded the threads. The cause: the stud had cracked and separated about a half inch into the alternator and had been welding and unwelding itself to the point it had every color of the rainbow burned into the stud. I went the Remy Delco 28SI route as other have had great luck with them here and on that other RV owners forum. Easy install, direct fit, and my local heavy truck shop had one at a very good price on the shelf with a new pully. Now, I have an alternator generating voltage in the low 14's at high idle reliably. As I state in the title of this post, I have removed the connection between the house and chassis 12v systems and will be placing a DC-DC device between them in the future. The problem is, I fixed it too well. Now, the engine does not stop until I turn the disconnect switch off. My assumption is that by removing power to the ECM, it is signaling the fuel shutoff solenoid to fire. I have all three terminal connections reconnected on the new alternator. There's the ground and positive lugs + 3 connections: Relay, Ignition, and DUVAC/Remote Sense. The Remote Sense is a 20amp fused connection to the battery distribution stud. Now harm in leaving that connected. I did remove that fuse to see if that was the source of a back feed to the ign line, but it kept running. I'm ruling that out. The Relay is a possibility, but I am not sure that would do it. Plus, that is the terminal signaling the tach. It is listed as half voltage (6ish v). I suppose that could be it if the HAMSAR 6v Alt Fail relay is stuck, but it was fine before the alternator swap. My hunch is that it is the Ignition connection. Others have had this issue and have left the IGN terminal disconnected from the alternator. I've been reviewing the chassis schematics for my rig, and it doesn't appear that it is a critical connection for the system. Any unintended consequences for leaving the 28si disconnected? The 28si is self-exciting. The installation manual explicitly states that the alternator works fine with only the positive and ground connections made. (Though the RV does need/use the relay connection). My next step in troubleshooting is to remove and tape the ignition connection that goes to the alternator. Any other thoughts on this subject? I searched "Engine won't shut off" on the forum and didn't find any posts about this topic. Cheers! Brad Edited January 25 by Bjohnsonmn Adding photos and images Link to comment Share on other sites More sharing options...
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