1GM10 intermittent charging alarmm

[Behome]

1GM10 charging alarm sounds shortly after starting and continues or stops after a few minutes. At few thought a slack alternator belt but retensioned, also replaced water pump impeller. No issues previous to the other day on our shake down cruise.

 

[VicS]

Bad connections?
Alternator brushes worn? /Commutator needs cleaning?

But if the audible alarm is sounding surely it is due to a low oil pressure alarm, overheating alarm, or water in saildrive seal if applicable. I did not think the no-charge warning
sounds the audible alarm.

 

[Daverw]

charging light does not sound beeper, as VicS says, oil or temp alarm

 

[Behome]

Neither the water or oil lights are showing only the charging light. As I said, as a precaution I changed the impeller and checked the oil. However the flow from the exhaust may be a bit less than usual....

 

[Behome]

Next visit I'll check connections to panel, didn't have my meter handy last time.

 

[Daverw]

Assume you’ve checked the bulbs are ok

 

[Behome]

No next step I think. I assume oil pressure light should come on before as soon as power turned on.

 

[Behome]

Could it be a dodgy thermostat?

 

[VicS]

No next step I think. I assume oil pressure light should come on before as soon as power turned on.

Could it be a dodgy thermostat?

At switch-on the no-charge warning light should come on. The low oil pressure light should also come on and the audible alarm should sound.

Once the engine is running both lights should go out and the audible alarm should stop.

If the oil pressure fails the warning light should come on and the audible alarm should sound.

If the alternator ceases to generate the no-charge warning light should come on but this should not cause the audible alarm to sound.

If the engine overheats the high temperature warning light should come on and the audible alarm should sound.

If the thermostat fails to open the engine will overheat and trigger the high temperature alarm.

 

[Behome]

Thermostat out and tested, works fine.
Alarm bulbs for oil and water found to be hanging loose behind panel so not visible from front but working. Next step to refit thermostat and check alarm connections and then see which alarm light comes on.
My utter ignorance of the system is very evident so thanks to those who have replied.

 

[Daverw]

Easy way to test each is to disconnect temp connection from sensor and restart, sensor switch closes on high temp. We’ve just had unexpected high temp alarm, upon checking water pump found strainer blocked, cleared and still high temp alarm, changed impeller and still high temp alarm. What we found was that temp switch had seen high temp and stuck closed. changed switch and all good

 

[Behome]

To trythe disconnection on to or rows high tide. Last chance until next springs as I'm in a mud berth.
Still have charging light on plus sounder goes after about 10 minutes running - neither oil nor water lamps come on but water flow appears to less as engine warms up. It's. Been suggested I remove the thermostat and run engine again To see what happens.