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I have an hour meter for my engine in the middle of my tachometer. It has stopped incrementing when the engine is on. I pulled the tach (which works fine) and all of the four wires that attach to it are well connected. How can I go about troubleshooting this? Is there a common failure mode for these?

The engine is a Westerbeke diesel, a 1973 Four-91. The tach is an aftermarket part from Motorola. The hour meter set into it is analog - it looks like a small odometer.

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Is the hour metal digital or analog? –  Parker May 18 '11 at 13:33
    
Make, Model, Year? –  Larry May 18 '11 at 17:46

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up vote 3 down vote accepted

If it's analog, the tachometer itself works, the signal wires are connected and sending signal (use a multimeter to test the actual voltage, the wire(s) could be damaged), then it's possible that the hour meter is broken mechanically. It seems to me like investigating warranty replacement may be the best idea if applicable.

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Typically the hour meter inside of a tach is driven off the same input as the tach itself. If there's any signal to drive the tach, the hour meter is driven (usually as % of RPM, so 1 hour at 100% = 1 hour indicated and 1 hour at 50% only shows 0.5 "hour"). There are hour meters driven by oil pressure, but that's typically a stand-alone unit (and measure hours like a normal "clock" hour). –  Brian Knoblauch Apr 5 '12 at 19:46
    
One hour at 50% throttle turns the hour gauge only a half hour? I had no idea! Wow, thank you for sharing this! This raises a question though: how does the hour meter know what my RPM range is? E.g. this engine idles at 300 rpm and the governor limits the high end at 2300 rpm. Do I have to calibrate it? –  Justin R. Jul 18 '12 at 22:30

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