Yanmar 4JH4-TE Alarm Not Working

[67Therapy]

Need some troubleshooting advice. Yanmar 4JH4-TE. When the key is placed to ON, the Battery picture (Alternator) light illuminates (correct as designed) and the red low oil pressure light on the oil pressure gauge illuminates (correct as designed), however the alarm is not sounding as it normally should.
When engine is running, the oil pressure is normal, light is off and alternator light is extinguished.

Took the panel off...removed/reset some plugs...took a general look around...drank a beer. Put it back together. Problem still exists.

The alarm itself is a piezo on a printed circuit board...next trip to the boat, I was thinking I could meter the poles of the speaker for dc volts when the key is on.

In this thread someone had a similar, but opposite problem (his alarm won't turn off) and he determined it to be an alternator issue. I only mention this because when the engine was running, my Raymarine ST 60+ graphic display was alarming low volts...8.9v. This was new also and may be completely unrelated...or not.

Thoughts? Troubleshooting ideas?

[MARINE ENGINNER]

i recommend you to check your dc voltage as you mentioned , the buzzer maybe ok , the voltage ok but the current (amps) low.if the wire is corroded the amps do not pass

[67Therapy]

Thank you. I went to do some testing today, but low and behold, it was working fine. Glad it's working, but intermittent gremlins are frustrating.

[svinshallah]

If the oil pressure light comes on when the engine is not running and goes out when the engine starts, then the alarm switch is properly connected. The little PC board has several diodes that allow the alarm to sound when any one of the lights comes on. It sounds like you have either a bad alarm or a bad sounder. If you're handy electrically, there is nothing on the board that is complicated. The Yanmar replacement part is pricey.
Rick
SV Inshallah
Balboa YC, Panama