Onan trouble

A freind called today and said this weekend his generator would start and run as long as he held the start button down. as soon as he let go it would die instantly. He is a mechanical type guy and I asked all the normal fuel and spark questions and we determined it was an auto shut down built in if the board does not see voltage. My guess is Voltage regulator problem. Any further input from the gurus on the friendliest place on the web for anyone with an RV or an interest in RVing?

wayne

Oh 98 Jamboree with a 4000watt Onan don't know the model

That's what mine did and yes for me it was the regulator. There can be other problems that will cause this problem to . I got a great web site that had very good troubleshooting charts. I will try to find it but I typed onan generator will not start and got the site.

I just went through this with my Onan 4KW Emerald zukIzzy. It could be several things...tell them not to start throwing parts at it until they know for sure what it is. It can get exspensive real quick. The circuit board in onans does and monitors several things before it will allow the genset to keep running. It first sends voltage to the fuel pump, the ignition, the choke heater, the start solenoid, and the field flash circuits (that's a DC voltage across the stator to energize it) At this point the engine cranks and starts. In the first couple of seconds oil pressure is built up and generator volatage is built up. Once the board senses the oil pressure and AC voltage, it cuts off the starter solenoid and the field flash circuits, but keeps producing ignition voltage to keep the genset running. If either AC voltage or oil pressure is not present it will not allow the genset to keep running. The most common three culprits are dirty slip rings (A lot of rv's are stored for long lengths of time without generators running and the rings get oxidized) these can be easily cleaned, or it could be the circuit board itself, or the voltage regulator. It could also be low oil pressure or bad oil pressure switch (but not as likely). I'm posting a web link for you that you can copy and paste that is awesome for troubleshooting Onan gensets...it's a PDF file and you can print out the whole thing and just go right down the list. It's from an online after market generator parts supplier (flightsystem.com) that are really helpful (plus the aftermarket boards and regulators are a lot less exspensive). They also sell a $20 tool to clean the slip rings...Check it out and good luck. http://www.flightsystems.com/pdf/onanrvtshootgd608.pdf

Excellent advice from Bernhard - I can't think of anything more.

I typed a thankyou post but it went away :-[ me and my fat fingers :.

thanks for the help that PDF is just the ticket. I had forgoten about the slip ring corosion. we will go thru is all when he gets to my shop next weekend.

wayne

Thanks Gary.....If you ever see a problem with an Onan about the hour meter running and the remote switch light being on when the generator is not running....it's probably not the generator, but a bad power converter allowing trace AC voltage to get to the circuit board (making the circuit board think the generator is running) I found that out with mine after dumping $900+ into my generator.

i would look at the main control board , 2 screws on front board with switch will come out take too your dealer have them check it , an some off those Gennys have a little REctifier behind the board that can give you a FIT !! Good Luck !!!  Rod