No AC output on Onan 15KW

[Top Shelf]

Hi Folks, The Onan 15KW on Top Shelf has always been pretty reliable and bullet proof. It had been a month or so since I ran it and this past weekend I went to start it but the battery was low and wouldn't light it.

I turned the 12vlt battery charger on overnight and the next morning it spun right up and runs fine. The problem is there is now no electrical output. The frequency meter is dead and there is no voltage making it to the panel. The Emergency stop SW seems fine. It will shut down the genny while it's running and there will be no start when the Stop Sw is "ON". Won't even run the starter. The 50 AMP pop out breaker seems fine.

It is hard to get into that control box with little room to work once you get there. Any thoughts on this....would a weak battery cause that 50 AMP breaker to open and then not re-set? Am I correct in assuming the frequency meter is driven by AC and not some mechanical means? Anyone have a similar issue? Thx.

 

[rsmith]

The Ac side and the Dc side are not interrelated. You need to check all fuses selectors and breakers in the Ac circuit. The HZ meter is powered by Ac current

 

[MarioG]

Reset the main output breaker that should be located close to the generator. If that doesn't work, you might need to flash the generator.

 

[captddis]

Just replaced a exciter stator in a MDL3. Had the same symptom. Everything comes in three's.

 

[Top Shelf]

I had actually forgotten about the main 50 AMP circuit breaker. In this case it's on the side of the control box on the generator itself. So not in plain sight. And I was sure it was gonna be open.....well not so. It seems to function fine, at least mechanically. As far as I know, that's it between the genny and the control panel. No other AC breakers.

I didn't have time to dig into it tonight. But what I did notice was.....with the breaker closed. There seems to be some slight movement on the Hz meter. This is one of those meters that look like a row of teeth and scaled between 45 and 65 Hz, anyway some slight movement around 60 Hz. On the analog volt meter however, 25 volts......when I open the breaker, both go to zero.

Would there be fuses in the control box on the Genny? Any thoughts on the 25 volts? Thank you.

 

[gbharrington]

I had a similar problem. It turned out to be a corrosion induced open in the exciter stator winding. Get your ohm meter out and see what you come up with.

 

[Top Shelf]

Thanks for the input guys. I'm going to be on the road all next week and won't be able to work on it.

In the meantime, does anyone have softcopy of the Manual for an Onan 15MDL3J? I had it on a previous laptop and evidently it didn't make it to this new one. Clearly a huge mistake on my part!! Thank you.

 

[GJH]

The best I can do is the following link for the complete generator end service manual. I can also e-mail you a pdf of the basic owners manual for the entire set.

http://asavage.dyndns.org/Onan/display1.php?Path=934-0500&db=Onan&table=934_0500&Page=front

 

[Top Shelf]

Thank you George! That link will be plenty good reading next week. thx.

 

[Top Shelf]

OK, back in town and have some time scheduled to work on this. The manual is a big help George, thank you.

I've trouble shooted (sp?) to where flashing the exciter coil is next. Evidently I'm looking for an F1 and an F2 terminal or lead......having been all through the control box with limited access and visibility (I might add). I can't figure out where these are located....Are they in the control box or down by the exciter coil itself?

Many thanks.

 

[captddis]

F1 and F2 are connected to the bridge rectifier.

 

[Boatsb]

F1 and F2 are connected to the bridge rectifier.

What river does that cross?

 

[captddis]

The river of dreams

 

[Top Shelf]

Well this has been a while and is now turning into a sad story...... After wringing out the Bridge Rectifier, cleaning up the transformer terminal block connections, we were making AC again.......until the very next weekend. Then same old problem......23 or 24 volts on the house meter.

Since I've been spending a lot of time there I also noticed I had a potable water leak from a copper crimp on that grey plastic pipe.....right where it goes through the bulkhead to the cockpit. It runs down the bulkhead and puddles under the genny before it finds its way to the bilge. Not sure this was a contributor, but certainly didn't help, I'm sure.

I've pretty much given up trying to fix this myself, don't have the time and I'm too big to sandwich myself into the space and be able to spin wrenches.

So I called a genny service company. They pull the electrical end cover off and indicate the stator and another stator are rusted and swollen. In fact when the Tech runs it he can see arching and sparking. Maybe the reason for the intermittent good and then no good. I don't know.

Anyway....we all know where this is heading....."death by a thousand cuts" as in having the electrical end rebuilt and R&R or pop for the new one.......

Boat is a 1989 48 CNV. Not sure it can be taken out in one piece........Thoughts? Thank you.

 

[Canuck Dennis]

I have a 20 KW onan that had to have the back end "serviced" that was according to the "experts" had the whole thing off the boat and "serviced" no improvement, was the VR that was shot. So, taking off the electrical end is possible but a pain if tight for space and worse to re install due to alignment. So now both gens are on st stl bases so I can slide them around if needed for serious work. swapping the back end out for a Marathon end may be the least expensive but no idea how the controls would need re work.