Warning alarms

[MarioG]

My water temp and charging alarms are going off after running an hour or so with a Yanmar 20qm20h engine sea water cooling. I know the alt is charging and the engine is circulating water and it doesn't feel real hot comeing from exaust, nor does the block feel to hot. I did an ohm read on the water temp sensor and with engine off will read ground on wire running to sensor termanal.

I'm lost at what I should be looking for. Any help and suggestions will be appreciated.

[tommays]

The alarms are just switches which compleat the circut to the buzzer when they reach there set point and would generaly be for water temp and oil pressure

senders do the OHM thing to a guage to give a temp or oil reading

The temp of the exaust water has littel to do with motor temp

[erps]

My water temp and charging alarms are going off after running an hour or so with a Yanmar 20qm20h engine sea water cooling.

Do they go off at the same time? Does the charging alarm go off before the temp. alarm? If the charge alarm goes off and then the temperature alarm goes off a little later, I would check the fan belt while the motor is running to see if the alternator and the sea water pump are still spinning.

These are strange symptoms you're experiencing. In past circumstances where I've experienced real weird electrical symptoms, the problem has often been a ground problem. Accessories do wierd things when they're looking for a path to ground.

[MarioG]

They go off at the same time and both go off if a take the wire off the water temp sencor, its brown. I think it may be a ground problem. M repair manual doesn't give me a good wiring diagram. Its a old boat hard to say how much the system has been messed with? I
m hopeing to hit a boat yard soon if I can't get it figured out.

[LakeSuperiorGeezer]

Originally Posted by erps

...In past circumstances where I've experienced real weird electrical symptoms, the problem has often been a ground problem. Accessories do wierd things when they're looking for a path to ground.

With both alarms at once, apparently with normal temperature and alternator, I am also thinking a ground problem, probably in the instrument panel. Start by giggling wires around while underway.

[erps]

I think your temperature alarm sending wire (which is looking for a path to ground to activate) is in partial contact with your charging idiot light wire and feeding back through the instrument panel. I would test this by bypassing the temperature alarm wire with a separate temporary wire to see if the problem goes away. If it goes away, I would start examining the wiring harness between the instrument cluster and the motor and pay good attention to sharp bends or where the harness goes through choke points, as this is where it will most likely chafe.