Onan Generator - Only kicks on after being on the road

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stingme62

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Joined
May 28, 2019
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5
Any thoughts? I have an Onan Marques 5000, it has less than 400 hours on it. Recently I replaced the pump and after that when I fire it up it runs fine but doesn't engage. If I take the RV down the road it will randomly kick on. Any thoughts?
 

Larry N.

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May 26, 2010
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Westminster, Colorado
I'm not sure what you mean by "pump." Is it the fuel pump? And what is "engage?" If you would mention the rig it's in that would help, as some have automatic transfer switches and some have to have the shore power plug be connected to a special generator hookup, assuming that by "engage" you mean you don't get power from it into your rig.

So please get back to us with more info, such as what your rig is (year, make, model), and perhaps other information you might have.
 

stingme62

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Joined
May 28, 2019
Posts
5
Thank you for your replies. When I say engage, means I've started the motor but there is no power going to the transfer switch. I have started it and put my multimeter on it to check the two 115 poles and get no power. When I drive the RV around while on the road when the generator is running it randomly will start getting power and everything is working. The "pump" is referring to the fuel pump, sorry about that. I've sprayed electrical cleaning solution on it but that didn't do anything.
 

Isaac-1

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Dec 3, 2016
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Are you sure there is no power going to the transfer switch, or is there no power coming out of the transfer switch?    The generator should shut down after a few seconds if it is not generating AC power.

If it is no power coming out of the transfer switch, my first thought is possibly a sticking relay in the transfer switch, or other wiring fault.
 

stingme62

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Joined
May 28, 2019
Posts
5
The old fuel pump on the generator went bad. I had no issues with the new pump the unit started right up. I put in a new transfer switch and checked it out, it was fine. I went back to where the wires first come out of the generator to see if I had power, which I wasn't getting any. I checked to make sure there were no issues with the neutral wire which was ok. I put everything back together, started it, motor runs fine but no power to the transfer switch. I get it out on the road and leave my AC unit on after driving a while I will feel the cold air and will know the power has kicked in. I wasn't sure if there is another module that could possibly be lose. 
 

stingme62

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May 28, 2019
Posts
5
This unit has two circuit breakers, I could see one maybe going bad but not both of them.
 

Gary RV_Wizard

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Feb 2, 2005
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West Palm Beach, FL
Those two breakers probably have a plug on an internal wiring harness and either the plug connection of the wires themselves could be intermittent.  Everything you describe indicates that either vibration or heat is causing contact to be made, so you are going to have to slog through wiring and the components to see where it is.

Have you tried letting the genset run while the coach sits still? I'm thinking it may be heat expansion (rather than road vibration) that is affecting a component or connection.
If you can't find a free service manual online, there are usually inexpensive one on CD on Ebay.
 

stingme62

Member
Joined
May 28, 2019
Posts
5
Thanks Gary, I will try looking into the breaker wiring. I'm praying it's something simple or loose! :)
I have let the generator run a couple of times now while the RV is just sitting but nothing happened.
 

Lou Schneider

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Mar 14, 2005
Posts
11,791
And try banging on the ass end of the generator while it's running.  You could have stuck brushes that are preventing the regulator voltage from getting to the slip rings.

If dirty brushes or slip rings are the problem Flight Systems has a nifty slip ring cleaning tool

The 10 minute video on their home page shows the connector you should make sure is seated fully, if that doesn't help it shows how to use a multimeter to test your generator's rings, stator and slip rings via that socket:

https://www.flightsystems.com/

They also make excellent replacement regulator and control boards if that turns out to be the problem.

And if that's not enough, there's a button at the top of the page to let you make an appointment for 30 minutes of free telephone tech support if you get stuck.

Yeah, I like their customer service attitude and the stuff they make.  But there's no connection beyond my being a very satisfied customer.



 

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