GB36 Power Breaker Tripping

[Gdavi2535]

Hi,
First post here… our 1988 GB36 Classic has a single Cummins 210 engine. On Monday after returning from a weekend cruise, we slowed to bring in the dinghy at the harbor entrance, but noticed that all the engine instruments lost signal. No tach, temp, pressure on both upper and lower helms, but the engine was still running fine.

We revved back up to get her to the mooring then shut off the engine. At that time I noticed the engine Power breaker was off. Odd, since that breaker is switched on to start the engine.

I restarted the engine and revved her a little. The Power switched tripped off. I flipped it back to on, revved it again and it tripped again. Seems it trips with any moderate RPM’s.

It’s a hellishly busy time of year for diesel mechanics so I’m hoping to try to diagnose this further this weekend. Thinking maybe a loose ground, an alternator load issue, or even a bad breaker, or ??

Any thoughts on what may be causing this or how to diagnose it would be greatly appreciated!
Gary

 

[tiltrider1]

You don’t need a mechanic. You need an electrician. A faulty breaker is possible but not likely. More likely there is a short in the system. Look for loose or frayed wires that create shorts. If you know how to use a multimeter you can do a continuity test on various components looking for a short.

 

[Cigatoo]

You don’t need a mechanic. You need an electrician. A faulty breaker is possible but not likely. More likely there is a short in the system. Look for loose or frayed wires that create shorts. If you know how to use a multimeter you can do a continuity test on various components looking for a short.

I would agree with this. Remember your diesel will run without electrical power. That breaker is tripping for a reason. Either it is sensing an overload / short circuit or it is defective. Either situation is a distinct possibility. The good news is that it appears to happen all of the time versus intermittently. That makes it much easier to diagnose. A good marine electrician should be able to quickly find the cause. Please keep us informed of the outcome.

 

[High Wire]

Welcome aboard!
The breaker trips from high current like a short to ground. Inspect the engine harness with a bright flashlight. Tug gently on every connector. Look for disconnected crimp terminals. Look for frayed insulation or copper wire touching the block. Also check the back of the instrument panels, FB and Lower. The instruments and alarm are powered from the same breaker.

Questions:
If you turn on the breaker but don't start the engine, does the breaker still trip eventually?
Try finding the engine harness plug at the engine. Does it make any difference if it is disconnected? Find the other end of the harness behind the helms. Repeat

 

[SteveK]

Since it is raised rpm trip, could the alternator output cause this?

 

[tiltrider1]

Since it is raised rpm trip, could the alternator output cause this?

Yes, but more likely that the higher RPM is causing some component to reach a short phase. Not seeing the wiring puts me at a complete disadvantage. It would not be normal for the alternator to flow through the engine circuit but that doesn’t mean that in OP’s case it doesn’t.

 

[Comodave]

Maybe start the engine and go around and wiggle the wiring harness. It may be at higher RPMs the engine is vibrating and causing a wire to tough something that is grounded, like the block, and shorting out causing the breaker to trip. Look for cracked or worn insulation on the wires that are powered off this breaker.

 

[Gdavi2535]

Thanks to everyone for their great feedback! I got lucky and found a mechanic who could visit the boat today for a look see. He quickly found that one of the posts on the alternator had broken inside the housing. He removed the alternator and it’s getting a rebuild. Will hopefully know for sure that was the issue when we get it back onboard next week. Stay tuned!