Problem Or Not?

[Edward Buker]

I had the generator running in our 2002 Marquis. It was time to head out for a return trip home and I started the C12 engine. In the process of starting the main engine the generator died. The generator restarted fine. I reasoned that the C12 starter pulled enough current while cranking that the voltage dropped below the level that the Onan 10KW generator engine electronics will tolerate and still run. I know all the battery connections are fine, including those to the generator, that the starting batteries are less than a year old, and they were fully charged.

Have any other owners run into this quirk also? It would seem that this could be a normal occurance.

Later Ed

[Gerald Farris]

The theory of the starting current for the C 12 being too high for the generator to provide does not hold true, because the generator does not charge the chassis batteries.

 The generator only produces 120V AC and charges the house batteries through the inverter/charger. The chassis batteries are recharged by the engine alternator or the Echo Charger with current from the house batteries at a maximum rate of 15 amps.

I can not think of any link between the generator and the C 12 that could cause the generator to die when the C 12 is started since they do not even share the same fuel supply line. It must be a coincidence.

Gerald

[Richard And Babs Ames]

Ours has done it a few times over the last nine years and it has not been a big deal as the genset started right back up. I think the vlotage surges before the controls kick in causes the hiccup. You may go several years before it happens again.

[Edward Buker]

Richard and Gerald,

It is good to know that someone else has experienced this same quirk. I feel better about that.....

Gerald, the root cause of the generator shutting down that I am proposing, is not related to a charging issue from the generator. You are right that the generator primarily charges the house batteries via the Xantrex and that was all working fine. It is that the generator shares the chassis batteries with the C12, and while the generator is running it is monitoring itself and using some electronics to manage and control its operation (like over temp, low oil pressure, holding the fuel solenoid open and pumping fuel, etc.). While you are cranking the C12 my guess is that the 12V chassis battery wiring harness that provides the necessary continuous operating voltage that the generator requires drops to maybe 8 or 9V. During that interval, voltage wise, I am thinking that we dropped below the voltage operating window required by the generator electronics to sustain running and it shut itself down. The generator was running several hours and just died while cranking the C12 and then it restarted immediatly without any hesitation so my thinking is that this was not coincidence.....The shut down timing was just too perfect. Ponder it a bit and see if you can end up in the same boat (RV) with me on this one...

Later Ed

[Gerald Farris]

I understand your viewpoint, and since the generator does not produce 12V current and has to depend on the chassis batteries to keep the 12V fuel solenoid open, the voltage drop on the batteries when cranking is apparently the link.

Gerald

[Edward Buker]

Great minds think alike....(with my mind it is more trial and error at times) thanks again.

later Ed

[Jerry Pattison]

Happens to me all the time.  Generator on, start engine, generator dies.  Start the generator again, no problem.

[Edward Buker]

Thanks Jerry,

I think this one is closed out. This seems to be an explainable and reasonably common occurance.

I think because the generator is likely running under load, with some electrical equipment and air conditioners operating, I would consider first shedding the loads, then open the main breaker. I would then shut the generator down. Once the generator is off I would start the main engine, then restart the generator and close the main breaker. I would add the loads back in once the transfer switch has thrown.This would probably be a safer way to operate given this interaction.

Later Ed

[Tom and Pam Brown]

Had the same issue and it finally started shutting off when I moved the coach.  Took it in to ONan and they found wires that had rubbed together and was creating a short on the fuel relay.  While the gen was removed from my 99 marquis, I had the belt replaced and a service performed.  I also replaced the fuel line because of the age of the hose.
This may not be your issue just thought I would give some other input.

[Richard And Babs Ames]

One thing I found out the hard way. Your Genset starts and requires power from your starting (chassis) batteries to run and after hurricane Charlie when I used it for 180 hours without starting the coach had dead chassis batteries. Beaver had not made a provision to recharge the chassis batteries. An Echo charger solved the problem.

The load placed on the starting batteries when you start the motor can cause the voltage to fall momentairly enough to allow the fuel solonoid to cut off the Genset. We just got back from a trip where we started the coach several times with the gen set running but we recenty installed new chassis batteries.