Carlos G

Good morning, I'm having a problem with the tachometer—it's stopped working. It had been working the entire time the boat has been in service (16 years) until they replaced the heat exchanger on the engine—a Volvo D1-20—which required disconnecting the wiring, and they must have left some wires loose or poorly connected. The thing is, everything works except the tachometer—specifically, the needle doesn’t move; it’s dead—but the hour meter does work. So I understand that the tachometer isn’t broken, but rather that it isn’t connected properly. The engine runs perfectly, but it really bothers me to drive by ear, not knowing what RPM the engine is running at. On my engine, the tachometer connection goes to the alternator, connection “W.” I’ve noticed there’s a loose yellow wire coming from the electronic control module, and I don’t want to mess up by connecting it where I shouldn’t. I’m trying to identify the “W” connection on the alternator, but I can’t find it. I’ve removed the instrument panel, and the tachometer connections look fine. I’ve read the repair manual and checked that the tachometer sensor, which is mounted on the flywheel, is also in good condition. I think the problem is either with the “W” connection or the electronic control module. But before the mechanic worked on the engine, the tachometer was working correctly. If anyone has the engine’s electrical diagram so I can identify the loose wire and fix the problem, I’d really appreciate it. Thank you very much. Best regards.