All, Yesterday on the way home from a fantastic four days on our boat at Isthmus Cove, Catalina Island the tach for my Yanmar 3GMF engine panel started developing St. Vitus Dance. That is to say that after settling on an engine speed, the needle would bob back and forth varying as much as two thousand RPM's until it finally settled down after about 10 minutes or so of engine operation. It's a relatively new tach, one I bought last year to replace the original (I presume) that developed a sluggish needle and would take for ever to settle on the chosen RPM. For those wanting to know, the tach is a Nippon Seiki N-2 model, reading 0 to 4,000 RPM on the face. I'm pretty sure I replaced the sending unit last year too but forgot to check for loose wires on it yesterday after we got back. Has anyone else had this occur and if so, what was the fix? I'd hate to buy both parts all over again only a year later. Thanks for any ideas, suggestions and help, Glyn Judson, E31 hull #55, Marina del Rey, CA
Jittery tach.
- Thread starter Glyn Judson
- Start date
u079721
Contributing Partner
My tach had similar bouts of the jitters, and would from time to time just up and die on me. Wiggling the wires that were fastened to the back of the tach would usually bring it back to health - an effective if somewhat crude solution. On one rainy day at anchor I finally got tired of it, and replaced the fittings on all the wires that led to the tach. Problem solved. (Be sure to note VERY carefully which wire goes to which stud!)
So while it certainly might be a sender, in my case I am pretty sure that one of the connections inside the wire crimps had either broken or come loose.
So while it certainly might be a sender, in my case I am pretty sure that one of the connections inside the wire crimps had either broken or come loose.
Rocinante33
Contributing Partner
Glyn,
I too suspect a bad connection, or a bad wire. I am not sure what type of sending unit you have, though. My tach, and many diesel tachs, run off of the alternator. Do you have one that senses the fuel pulses from the injector lines? If not, how does the sensor work?
I too suspect a bad connection, or a bad wire. I am not sure what type of sending unit you have, though. My tach, and many diesel tachs, run off of the alternator. Do you have one that senses the fuel pulses from the injector lines? If not, how does the sensor work?
Hi Glyn,
I think we might have a consensus. Before I threw the 3GM30F in this past winter, I went through this on the 2QM15. Turned out it was a bad connector on the sending unit side. As I think about the way the harness seems to connect on each end, I think the sender side has more strain on it than the tach side.
I think we might have a consensus. Before I threw the 3GM30F in this past winter, I went through this on the 2QM15. Turned out it was a bad connector on the sending unit side. As I think about the way the harness seems to connect on each end, I think the sender side has more strain on it than the tach side.
Keith, My sending unit is a ftting not too unlike a sprrk plug in appearance that screws into the bell housing. There's a permanent magnet on the flywheel that the sending unit responds to and presumably with a switch makes and breakes an electrical connection to the tach itself. I'll be down there in a few days to rebuild my Groco K-H head and will poke my nose in tehre to see if everything is hunkey dorey at the sender end. Thanks all for your input. Some times it takes a village to shake the cob webs from my head in order to address the obvious. Later, Glyn Judson, E31 hull #55, Marina del Rey, CA.