Engine Alarm Buzzer

[Duke 7184]

I have a 1982 Morgan 321 powered with a YANMAR 3GMD motor. I need to find a repalacement for the engine alarm buzzer. So far I haven't been able to come up with a part mumber. The current buzzer is manufactured by Hitachi and is wired for multipal inputs: low oil pressure, high water temp. My owner/operator manual only indictes that it is a "B-Type" alarm panel.

Any assistance you can give me will be appreciated.

Duke

[trantor12020]

what's wrong with your stock buzzer? does it use all 3 inputs or just 2?

[Duke 7184]

All three inputs are used. I failed to mention the charger is also attached to an input.
The buzzer has no audio even with 12 vdc connected directly across the input(s). I suspect that the piezoelectric crystal is bad. The buzzer is in a sealed housing so checking further for defective componerts - diodes, etc. - is imposible.

[neilchristophers]

VDO makes a multi input buzzer that fits in the dash 2in hole but if yours is mounted behind the dash there is no reason why you carn't use two seperate alarms [alot cheeper] Neil..

[trantor12020]

Duke7184, your buzzer model is WI1-05. Its one input and 3 output (negative as return) via 3 diodes. If the other two alarm works, then its probable the 3rd diode is faulty. You could wire two diodes to one of the working output thus making it as 2 circuit. That should solve your problem. When activated, the positive passes through the buzzer diode, then through to 1 of the new diodes to say Oil Pressure switch or Sail Drive Unit switch then to ground (negative). The buzzer maybe just alittle softer as there'll be 1.2V drop across the series diodes but I guess it won't affect much. The Hitachi buzzer doesn't come cheap.

[hellosailor]

Sounds like you could buy one loud buzzer for about five bucks from any electronics place and add three diodes for about 25c each. Or, just buy three piezo buzzers and separate the circuits so each has a different sound, too.

www.allelectronics.com one of many surplus & parts houses with this stuff.

[Duke 7184]

trantor, Thanks for the information. I will do a little research and see what I can find where and for how much. If you know of some places that deal in this type of YANMAR/ Hitachi components please pass them along. The diode "OR" circuit you discribe could be made to work even if only one of the alarm circuits were still functioning. However, none of the alarm circuits are working. That is why I think the piezo is bad.

hellosailor, I appreciate the input. I have noted the email address you provided and will check them out should I decide to go that route.

Duke

[hellosailor]

Duke, before you assume the piezo is bad? Use a multimeter or test light to check on it. It is also possible (I think) that if one diode shorted, instead of failing open, it would simply ground the other signals and prevent the piezo from sounding. (Which is why three separate circuits could be good, even though three times more parts could just give you three times more stuff to fail.)

[Duke 7184]

helosailor, as I have already stated, the diodes are encapsulated in a module with the piezo. Keeping it simple: I removed the Acoustical Warning Alarm Assembly (AWAA) from the cockpit engine control panel; thus, totally isolating it from the input sensors. I connected +12VDC to the appropiate termnal on the AWAA. Then, one at a time, I connected each alarm point/terminal to ground (the negative side of the battery in this case). The piezo never sounded. It may be the piezo is not bad - it could be a broken wire - , but without breaking open the AWAA module there really isn't a way for me to tell. At this time I don't want to smash the module. I have remounted it mechanically to fill the hole in the control panel to keep rain out.
Duke

[hellosailor]

Duke, actually you said "The buzzer is in a sealed housing " and a sealed housing can usually still be cut open. Encapsulated is indeed another matter.

"but without breaking open the AWAA module there really isn't a way for me to tell." There is a way to check, use a DMM or ohmmeter to test the circuit. If the diodes are all functioning, the circuit will show near zero resistance one way, and near infinite resistance with the opposite polarity.

If the resistance is the same (near zero) both ways, you have a shorted diode. You should also be able to test across each diode lead to the other two, which will tell you which one has failed--if it is a diode failure.

If it is a diode failure, a dremel tool can solve the encapsulation problem if you really want to repair them.