Onan 10KW Starting Problem

[Lee Welbanks]

     With this coach we always had a problem with the Onan starting. almost always would not start unless the Cat was running, then started fine. According to my wiring schematic the 12 Volt for the starter came out of the front run box with a 2 ga cable off of the Chassis Batteries. Have heard in here and elsewhere that the 06-07's were hooked to the house batteries. Raised up the coach and got under there to actually find out what was what.
      2 ga. cable off of the Chassis Batteries from the top lug on the buss bar, cable runs all the way back to the bulkhead in front of the fuel tank and back to the Onan, approx 22 ft. Did a little test, connected my Fluke to the 12 Volt lugs on the back of the Onan to see how much voltage drop I would get. 13.4 volts hit started dropped to 8.5 volts, no wonder it would not start.
     Went and got 20 ft of 1/0 welding cable and high quality 1/0 by 3/8" copper lug terminals, figured out where and how to run cable the shortest route possible. Ended up with 11' from the run box to the Onan. Soldered terminals on and shrink tubed the ends. On the run box end connected on the same lug as the 4/0 main feed from the rear also replaced the 4 ga. ground wire with a piece of the old 2 ga. cable, soldered ends and all. Zip tied all the wired up out of harms way nice and neat. I'll strip out the old cable later when its is cooler around here.
     Time to test: Hooked up the Fluke, 13.6 volts and hit started 11.8 volts, started in half a heart beat what a difference, now I can set up the auto start and not worry about the Onan not starting and the house batteries getting run down.

[Steve Huber]

Lee,
Glad you found the source of your problem. I  found a number of instances in my Contessa where poor crimps or overly long wire runs caused problems. Sure I've got some in the Marquis but haven't had any issues yet.
Know what you mean about the heat. I'm replacing the floor in the Marquis now and it's hot, even in my garage/shop.
Steve

[Edward Buker]

Lee,

I have an 02 marquis and it cranks slow but never fails to start. I have a symptom of low voltage in that if the genset is running and I crank the Cat it immediately shuts the genset down. Probably low voltage due to cranking puts the Onan monitor systems out of spec for one of the sensors. I'm sure the wire to our genset is also not hefty enough also, just not as severe a symptom. That was pretty low voltage that you had...good job.

Steve,

Is this a floor remodel with a wood or wood like product or are you replacing underlayment? I want to prevent any water damage problems, so if you have one, let me know where, so I can watch for any symptom before any real damage happens.

Later Ed

[Lee Welbanks]

Heck Steve we are almost neighbors in the heat, we'll be leaving again end of Aug to Calif central coast, need any help with the floor job let me know.

Ed: I would almost bet the farm you have cabling issues if your Onan stops starting the Cat. Sometimes you just have to sit and scratch your head looking at how some of this stuff is put together. I say "what the heck were they thinging?" then I realize they weren't.

[Gerald Farris]

Ed,
Since the cabling to the Onan is not flowing any appreciable amount of 12 volt current when the generator is running, I do not see the cabling as the issue causing your Onan to die when the Cat is started because there is no resistance to cause the voltage drop.

Since the cable to the Onan is flowing a negligible amount of current, the voltage drop has to occur before the cable run starts. If the cable to the Onan is ran from the started terminal, moving it to the battery terminal should correct the problem, but if it runs to the battery terminal, you just need more cranking amps from your batteries.

Gerald

[Edward Buker]

Gerald,

I have never taken the time to trace the Onan cable to see where it originates. I know it seems to crank slow when I start it but it has never failed to start. The Cat engine cranks just fine so I think I have more than enough cranking amps from the chassis battery set. You are right, there should be minimal voltage drop in the cable length to the genset when I am not cranking the genset so you would think that it would not react and quit like it does. It really is a bit of a mystery. If Beaver folks did take the genset 12V lead off of the Cat starter solenoid that might be a good explanation as to why it likes to die while cranking the Cat. Maybe when I get home I will trace it and see where the weak link is. Thanks for your thoughts.

BTW do you know where your genset 12V main cable ties in?

Lee, I have scratched my head several times :-)

Later Ed

[Steve Huber]

Lee,
Thanks for the offer. We plan to stay in AZ till the Kerrville rally but we do "escape" to our place in Show Low when the heat gets too bad and my wife can pry me away from one of my projects.

Ed,
I'm replacing the carpet in the living area with wood. I'll provide a complete summary with pics when complete. I used .25" plywood on top of the existing OSB to level the sub-floor with the plate covering the step cover. Gluing the wood directly to the plywood. The OSB showed no signs of recent leakage so felt pretty safe using the plywood. Old leakage signs were at the front of the slide (drivers side) and slight discoloration below pass side vertical windows behind sofa. Both areas had solid OSB and discoloration had faded considerably. PO had both areas worked on.
Steve