I have a 2008 Winnebago Journey diesel pusher with an 8000 kw Onan. What is the battery starter source for the Onan? Is it the house battery set or does it have it's own battery? It would not start today on it's own until I started the coach engine. Upon starting the coach engine, the onan fired right up. I did not disconnect the Aux battery disconnect prior to leaving the coach last month. I intended to just run the generator at load for a while when this problem popped up. Any words of wisdom? I am new to RVing and have only had the coach for about a month.
Most generators start from the house battery so check the voltage of your house battery and charge it if needed, it is probably real low or dead. Full charge would read 12.7 volts. The reason the gen set started after you started the coach engine is that the alternator put enough charge, about 14.1 volts, into the house battery to let the gen set start. By the way the gen set does not charge the battery, all it does is supply 120 V AC to the on board convertor and the convertor charges the battery.
2004 Southwind 32VS 8.1 Workhorse chassis
2002 CRV Toad
U. S. Gear Unified brake system
Retired Fire Captain, SFD
Mine was just like that also. My problem turned out to be several really dirty connections from house battery to gen starter. Probally the first time cables were cleaned and some replaced. Works good now. Easy fix but took more time than I thought it would.
(To cheap to buy new)
1990 37 ft 5th wheel that hasn't moved since 1996 (our best home)
1997 33 ft trailer (winter home in much warmer climate)
2005 25 ft M/H (our "stand up B" for traveling)
It would be worth your time to start taking notes on your rig. Some people have great memory and can recall detail exactly but for the majority, it is best to have notes. Make the rig a course of study, take notes and make diagrams of what you understand and then find convenient opportuities to test your understanding. Much of the controversy and difficulty in dealing with service departments comes from the lack of understanding on the part of the owner.
There are three methods of providing starting battery power to auxiliary generators, if memory serves from working on rigs. The most common two are that the generator's starting circuit is connected to either engine battery or house battery. The less common is to have a separate generator starting battery.
The separate battery can be the best solution where the generator is located in a rear compartment on a long rig, or where the generator is located in a trailer which lacks an engine battery.
It sounds likely that your generator obtains its starting current from the house batteries but the fact that it was able to start following starting of the engine may be coincidental or the result of a bad connection. FWIW, the comment: "The reason the gen set started after you started the coach engine is that the alternator put enough charge, about 14.1 volts, into the house battery to let the gen set start." is incorrect and may mislead someone. The time required to significantly charge the house batteries is far greater than that provided unless you had the engine running for 15 minutes or more before attempting to start the generator.
The rig's engine alternator may or may not have provided enough current to carry the load of the generator starter but more likely the fact that the isolation relay (solenoid) connected the engine battery to the house batteries provided the power. Simply turning the engine's ignition switch to "On" would likely have had the same result.
It is well to determine how your house batteies are charged by your converter as mentioned previously: "By the way the gen set does not charge the battery, all it does is supply 120 V AC to the on board convertor and the convertor charges the battery." Some converters have only a little "trickle charger" board on the converter which will take days to recharge nearly dead batteries. More modern systems have an intelligent converter which will recharge batteries quite quickly.
This statement is likely to be accurate, however some Onan generator installations which I serviced had a small flywheel mounted alternator on the Onan's engine. This small alternator was intended to charge the starting battery of a "stand-alone" generator installation and would charge the generator's starting battery, regardless of whether the generator started from any of the three systems. I have serviced systems on service trucks which used this engine alternator to charge the generator's starting battery and others which used either the house or engine batteries for generator starting. All of these installations would allow the generator's own alternator to charge the battery used for its starting.
I recall some service trucks which used the engine battery for starting the generator in order to allow the generator to be started in the even that the operator (frequently) left the lights in inside the truck so that the house batteries were dead. On other occassions headlights were forgotten which drained the engine batteries enough that the engine could not be started. In many cases, there remained enough power to start the generator which could run for long enough to sufficiently charge the engine's batteries allowing the engine to start. The unit's power converter could not charge the engine batteries and it was found that installing a by-pass switch opened up another "can of worms".
It may be quite important to your operation that you understand which system is in your rig.
It sounds also as though you need to find and clean all the battery connections, following which you will be well advised to spray the connections with some corrosion inhibitor. Ask if you do not have a preference and others will offer experience. My personal preference is to use a wax based product such as "Fluid Film" or "LPS" because waxes tend to remain in place well and seldom affect plastics and other materials likely to be in the area.
These events provide an opportunity to gain understanding of how your unit operates and you may find that what you learn from this, is very valuable down the road.
Please post back to report on what you determine and as to your progress. There is something to be learned by those of us "observing" from afar.
If you are close to someone who has an interest, you may gain either insight or shared understanding.