Ignition Key Buzzer/Alarm Problem

[Bwester]

Boat: 1985 Kadey Krogen 42 with Ford Lehman SP 135 engine. There is some sort of buzzer/alarm that is connected to the ignition key that is buzzing even after I start the the engine. Previously it would only buzz if the key switch breaker was turned on and the key was turned on. Maybe for safety prevention to ensure you don’t leave the switch on after pressing engine stop button to solenoid. Previously, after you pressed the start button and the engine started it would stop buzzing. I have also noticed it would buzz somewhat if I have been running a while and then pull the throttle to the lowest idle setting. To me that would indicate some possible connection to maybe the oil pressure. Yesterday after changing oil, filters, replacing raw water pump and impeller, I started the engine and the buzzer does not stop. Oil pressure is good (55), temp is good, water coming out of exhaust, no oil leaks, no water pump leaks, just the buzzer will not stop. Any trouble shooting help or ideas would be appreciate. Trying to get ready to leave Ensenada MX for La Paz in the next few weeks. Thanks so much. Barry Wester

 

[hytedin]

There are two oil pressure sensors on your engine—one for the dial psi reading and one is a pressure switch that is activates the buzzer until pressure is sensed. Neither are expensive.

Check the wiring for corrosion, but it’s likely the alarm switch is either plugged up or dead.

Contact American Diesel for part and manual containing schematics.

https://americandieselcorp.com

 

[hytedin]

PS. In a pinch, you can remove the switch from the circuit, but then you’ll have no worning so pay close attention.

 

[C lectric]

THe low oil pressure sw. has likely failed. They are normally closed switches so require the pressure to open and shut off the alarm.


*********I have also noticed it would buzz somewhat if I have been running a while and then pull the throttle to the lowest idle setting*********8


This can sometimes be cause by overfilling the crankcase. SOmetime it does not take much too much oil to cause this. Drop the level by 1/2 qrt..
What is happening , often, with a slightly too high level is the oil is getting whipped by the crankshaft which beats air into the oil, frothing it. When really running the oil pump will compress it enough that the pressure rises. When you drop revs the pump is no longer producing enough pressure to collapse the bubbles so the system pressure drops below the alarm switch setting triggering the alarm.

Usually only lasts a few seconds untill the air dissipates. Many engines have this problem, mine included untill I dropped the pan level. The Cummins 6B series with the shallow pan was very prone to this. But it can happen to any engine especially if the dipstick was improperly marked at installation time.

This can be exacerbated by the engine installation angle, by overfilling or combination.