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Joe, Marine Mechanic
Category: Boat
Satisfied Customers: 7251
Experience:  ASE, electronics, Marine mechanical and electronics, pwc, wiring, all around repair tech,
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Joe,I have a 3126 rated at 375 HP in my 38 ft charter vessel,when

Customer Question

Hi Joe,I have a 3126 rated at 375 HP in my 38 ft charter vessel,when the engine is started the alternator warning light won't go out and the alarm sounds,the tachometer also stops working,after a while everything is normal,then maybe in an hour back again light on alarm sounds,have tried all the connections,can't find any problems,I have also changed alternators,voltage is fine,must be something that is common to the tachometer and the charging circuit,Regards Mark
Submitted: 1 year ago.
Category: Boat
Expert:  Joe replied 1 year ago.
Hello Mark,
Thank you for requesting me and allowing me to assist you, my name is ***** ***** I will be happy to assist you with your concern today.
During the problem with the engine running and an voltmeter attached to the battery, what is the voltage?
Have you had the batteries load tested?
If you switch from starting to house battery and allow the engine to run from that, does it still have the problem?
At the gauges I would check if the loss is power or ground related and let me know which if possible.
Customer: replied 1 year ago.
Joe,The voltage is fine 28volts,didnt run her on the service battery with the coupler in but will do tomorrow,all batteries are good.
Expert:  Joe replied 1 year ago.
I take it you have the 24v system and not the 12v system then, correct?
Have you tested via voltmeter at the gauges for loss of ground/power during this problem?
Customer: replied 1 year ago.
Joe,Will get back to you as soon as I can,Regards Mark.
Expert:  Joe replied 1 year ago.
Good morning Mark,
Sounds good.
Customer: replied 1 year ago.
Hi Joe,
Tried running the engine on different ways,running ban k with coupling in etc,makes no difference.its not an alternator fault its an alarm fault,were not loosing any voltage on the dash panel.I think its got to be something common to the tachometer and alarm system,
Regards Mark.
Expert:  Joe replied 1 year ago.
Good morning Mark,
Using a voltmeter you would need to confirm that whatever the battery/charging system voltage is that, that voltage is the exact same measured (or very close to) at the positive side of the warning light, and on the neg-ground side it is a good solid ground. Most likely your going to find a bad wire or a loose or dirty connection and thus why it is related to multiple devices. The warning light looks for a voltage drop from where it should be. This means testing via voltmeter at the wiring to locate and pinpoint the problem area.
Thank you!
- Joe
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