Generator voltage and 12V system fluctuations

Ding...Ding....Ding! We have a winner! Chris Bryant....Come on Down.....

Picked up the RV today from my service dealer and you were right and it was the 50 amp resettable chicklet breaker. It would fully engage and work fine most of the time, but when it acted up it would flutter and cause the fluctuations on both the 12V and 120V systems. $5.00 part, but no room on the 12V board to put in a better one for now. Will do an upgrade and put in a better breaker in another location when time is available before next season.

Thanks again to everyone for the suggestions.

OK. Great suggestions, but I am at the limits of my electrical abilities.
Chris - you are correct....it is a 1" sq. by 1/2" thick type with a small black reset button on the side mounted on the back of a large printed circuit board. It receives the 12V output from the convertor.
MexicoWanderer - good suggestions. You all have helped me decide to have my RV service dealer chase this down from here rather than the Cummins/Onan people. I think something on the 12V side is getting ready to fail and not so much just a generator output issue. If it was generator, I think the Cummins service center would have figured it out in the 2 hours they ran the generator and could not find anything. And I had the now 14 year old generator fully serviced by them, complete with new brushes at 1000 hours three years ago and the generator has 1300 hours now.
It just seems to me that it is something on the low voltage side, and perhaps the resettable 50A breaker that is getting ready to fail and just not there yet. By the way, I have touched this breaker several times during all of this and it does not run hot or even warm to the touch.
Thanks again for all the input and I will reply with what we find out or if we add the capacitor.

Williebago wrote:
Had a chance to do some testing today. I have a Craftsman true RMS clamp meter so I wanted to see what the hertz was doing. Started up the genset and at first no flicker. With no load the voltage was pretty stable at 122V and would fluctuate maybe +/- 1V and the Hz was 62 to 63 Hz. Turned on a handful of lights, and started the refridgerator and one heat pump. Still no flicker for a while but then the lights started to flicker. While they were flickering, I measured 119 to 122V and 59 to 61Hz. Then the flicker stopped. The 12V breaker (50A) had flipped, so I reset it. Flicker stopped before I could get any more readings and never flickered again. Genset just purred like a kitten.

Your No Load voltage is NOT correct. It has to be 126 to 132 and 60 cycles. Failure to get your Genset to spec just makes you spin your wheels trying to find the problem. GET THE GENSET TO SPEC, then see if you have a problem. You keep harping on it runs just fine. That does NOT mean it is running to spec. Doug

https://www.delcity.net/store/Hi!Amp-Surface-Mount-!-Manual-Reset-(Switchable)/p_811053.h_195738.t_1

Get a real circuit breaker not a Mattell reject :)

Agree with the checking/changing the 50 amp breaker (I assume it is the small chicklet type with the reset button on the side). 50 amps is a pretty big load, but flickering would indicate a bad connection inside the breaker, which would heat it up, tripping it at well below the 50 amp draw.

Check that 50 amp breaker. In fact, wire around it while experimenting.

With a P.W.M. charging regime it takes a peculiar pulse frequency regime for the power supply to track a voltage source. First eliminate potential spurious loads that can induce pulse induction with the converter. Shut off by pulling fuses one at a time while observing phenomenon. If all circuits prove innocent then load generator or inverter with 1,500 watt minimum load heater. If no change, further searching is up to you.
I do not see why a 5K 50 volt electrolytic capacitor cannot resolve this successfully. It is a 10 minute installation procedure.

What does the 12 volt 50 amp breaker feed? How does a 12 volt breaker flip?

This is where a scope-meter is worth its weight in tranquilizers. Try the capacitor I outlined above. It's an inexpensive potent fix.

Had a chance to do some testing today. I have a Craftsman true RMS clamp meter so I wanted to see what the hertz was doing. Started up the genset and at first no flicker. With no load the voltage was pretty stable at 122V and would fluctuate maybe +/- 1V and the Hz was 62 to 63 Hz. Turned on a handful of lights, and started the refridgerator and one heat pump. Still no flicker for a while but then the lights started to flicker. While they were flickering, I measured 119 to 122V and 59 to 61Hz. Then the flicker stopped. The 12V breaker (50A) had flipped, so I reset it. Flicker stopped before I could get any more readings and never flickered again. Genset just purred like a kitten.