Join Date: Sep 2010
Location: Boston area
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Rep Power: 7
Diagnosing Yanmar warning horn failure
I have a 3GMD with low hours, and all new Yanmar engine wiring harnesses, new tach & new Type B panel installed within past year as preventive maintenance after 25 years. I reused the horn, key switch, check switch and start button. This past weekend, when I turned the key to ON, there were no warning horns. Normal is for the warning horn to start immediately, and go off as soon as the engine fires. The engine then fired perfectly, seemed to run fine with no hints of poor charging, low oil or overheating. When I shut the engine down, after crossing my fingers and running it for a while, the horn stuttered a couple of times and then came on constant until I turned the key to OFF, just as normal except for the bried stutter before horn on constantly. After sitting a little while, I tried starting again, and the routine was just as the first time above - no horn at all when ON, or until after shutting the engine off, when it stuttered and came on full again. For clarification, this panel has three alarms: water temp, oil pressure and charging. Only the charging and oil pressure should trigger alarms when first starting, and both should start instantly when key is turned ON.
I did a brief check of all wires to see if anything appeared loose, found nothing. All grounds, etc. were renewed when I replaced the 3 wire harnesses. From the wiring diagram, the only common element seems to be where the positive power runs from the key switch to the horn (buzzer) on the panel. Each of the separate warnings is separately wired (positive and ground) after that. My initial sense is that the actual horn (buzzer in diagram) may be failing, but I'd be intrested to hear if this seems to be a familiar problem to anyone, or any hints to further diagnose on my next trip. An alternative common point is the key switch, but the same switch contact that has the wire to horn also has a wire to alternator that works perfectly.
Thanks in advance
1985 Marshall 22 catboat