Engine warning alarm

[Rxcape]

HI all: I have an issue with a starboard engine alarm light and buzzer remaining on after the engine has started even though the oil pressure and temperature gauges indicate the correct readings. The warning light/buzzer will waiver on and off but primarily on, almost like a loose wiring problem. I have checked the engine temperature with an infrared gun and the temp gauges are accurate. Both oil pressure gauges(helm & Flybridge) are reading the same and the engine does not heat up so my assumption is that the oil pressure is good. I have not put an external oil pressure gauge on yet as I find it hard to believe that there is an oil pressure issue based on the gauge readings being "normal" at the separate stations. Anyone have any thoughts?

Jim

[prowlersfish]

There is a oil pressure switch that turns on the alarm and a temperature switch that does the same both by grounding . one could be shorted or the wire grounded .


Its best to say what boat and what engine when asking these questions

[Rxcape]

Thanks prowlersfish..... Not sure I understand, are you saying the sending unit is just completing the ground circuit? I'm mostly concerned about the oil pressure. When I turn the key the alarm comes on until 2-3 pounds of oil pressure is detected closing the sending unit which turns the alarm off. Is my thinking incorrect? Wouldn't be the first time !

Both sending units are attached and grounded directly to the block, wouldn't the alarm be on all the time if it was a grounding issue? This problem just recently started....

1975 44' FBMY twin 440's

[captainmaniac]

You mention oil pressure at 2-3 pounds shuts alarm off... I don't have the specs in front of me but I believe you should typically have 40-60 PSI during normal operation. Can't recall if the oil pressure gauges / senders are based on a voltage or impedance system (thinking the latter), so if pressure is low or if there is a wiring or connection issue (ongoing or intermittent) the alarm sensor could see an impedance level that triggers it to go off.

Obviously, wiring issues could exist at either end of the wires, as well as along their entire length.

[prowlersfish]

When you have no oil pressure the oil presser switch is closed . This completes the ground on the alarm and alarm will sound . When you start it and get oil pressure the switch opens and the alarm goes off . The temp switch closes when the engine gets to hot . If the switch shorts or sticks the alarm turns on . If the wire to the switches gets shorted to ground the alar will sound . look at the wires and disconnect the switch(s) and see if it turns off ,that will tell you if its bad . Don't confuse the switches with the senders for the gauges

IZ am assuming you have good oil pressure . What are you reading when you start up ?

[Rxcape]

Thank you prowlersfish and captainmaniac....

prowlersfish.... I was confusing the switch with the sending unit ..... I was thinking of the circuit just the opposite of what you describe. Makes perfect sense now! I can see, now, where there must be a short in the line somewhere.

captainmaniac.... I was told the switch is sensitive at under about 5 pounds of oil pressure, when the oil pressure rises above that pressure the alarm goes off. Makes perfect sense after the explanation from prowlersfish....

My normal oil pressure is right about 60 pounds after the engine has warmed.

Thanks again to both of you for your help.....

Jim...