OnanCummings MDKBH with no power output while running

[Indolent58]

This is a head scratcher. Our generator has been working fine since we bought our boat. Last week we turned it on - it started normally and the digital remote panel reports it was generating 115v 60hz power as usual but no power was seen at our house or aircon manual transfer switch panels. The digital display reports no faults. The 30 amp breaker on the generator was not tripped and appears to be working properly. I tested it with the generator off but access is so poor in the aft lazarette I was afraid to check for voltage with the genset on. I tested the transfer switch breakers and have confirmed that the wires feeding them are not energized when the generator is operating. The manual suggested that if the generator runs but does not output power you should test the breaker but offers no other advice,

Anyone encountered a problem like this? Currently in Martinique and the service folks are booked out for weeks.

[skipperpete]

First check the source selector switch on the main board ! You’re going to need a multimeter and also develop an awareness of how dangerous it is to do AC circuit tracing and trouble shooting...... regard every connection as live, even the ground, I assume you have no earth leakage protection so this is more risky than a domestic or marina connection fault, maybe wait for the professional electrician.

[Tin Tin]

Pretty hard to diagnose with out a circuit diagram. You might find there is another breaker (a GFCI - 110V type) before the change over switch but that is just a guess. I assume you are not connected to shore power and that the shore power switch has been disengaged. If you have a smart inverter charger this may be be controlling AC power as well, check that it is on. Other than the simple stuff like switches I would not recommend testing live wires etc as a DIY exercise for non qualified persons. It might help to post a photo of your 110V distribution switch panel.

[Indolent58]

Originally Posted by Tin Tin

Pretty hard to diagnose with out a circuit diagram. .

Tell me about it. The Beneteau manual has reasonably good documentation on the DC system, but very little on the AC side and in any case it does not address dealer options like the generator at all. I am reasonably sure there is no additional breaker or GFCI between the generator and the transfer switch panels. Two 10/3 cables exit the generator into the bowels of the ship and two 10/3 cables emerge to feed the transfer switches. The Aircon transfer switch goes directly to the air conditioner. The general AC transfer switch goes to the inverter breaker on the main distribution panel and to the water heater. So all AC outlets do go through the inverter’s internal automatic transfer switch but the power isn’t making it to either manual switch or the distribution panel so it’s a moot point. I know my way around AC power and multimeters ( I build tube amps) but I will have to let a (hopefully small) professional check for things I just can’t get to. Fortunately I just upgraded to a high output alternator so the lack of the generator is not a big problem for now.

[Senojev]

Our Onan has two breakers, one on the front of the sound box top left on a panel but also another on the left hand side of the box near the top corner. Took a long time to find it when ours tripped.

[skipperpete]

The MDKBH manual , troubleshooting section seems fairly confident that its a breaker issue and suggests (engine not running) removing the wires and testing for continuity. They also suggest, reset, turn on or replace the main breaker and offer the same advice for any other remote breakers outside the control box. The troubleshooting guide also suggests that if a manual voltage selector is fitted it should be switched to AUTO. I couldn’t find any more info in the wiring diagram about this selector so it might not be a common addition. Be really careful when working on the dormant genset, I suspect it has autostart..... turn on a light switch or appliance and the genset starts immediately with no other help. I must admit , I’ve only worked on the larger direct drive model but I like the way Onan did the belt drive hookup, that makes it very compact indeed.

[wrwakefield]

I don’t have experience with your generator model, but wanted to share that the same can happen with our Fischer Panda 10kw gen if it is started up under AC load, or shut down while supplying an AC load of ~>10% or so.

From the manual:

Switch the Land Electricity/Generator Switch to Zero before Starting or Switch Off all the load.

The generator should only be started when all the load have been switched off. The excitation of the generator will be suppressed, if the generator is switched off with load connected, left for a while, or switched on with extra load, thus reducing the residual magnetism necessary for excitation of the generator to a minimum. In certain circumstances, this can lead to the generator being re-excitated by means of a DC source. If the generator does not excitate itself when starting, then [manual] excitation by means of DC must be carried out again.

In case this is relevant to your situation.

Cheers, Bill