Community Forums

Birddog Pilot · 08-01-2008, 04:28 PM

Here's an interesting problem. I've been running the Onan once a month as prescribed with a good A/C load; in fact that was just done two days ago with no problem. Now today we bring the Alpine home to load it up for a three month trip, leaving tomorrow – not going to happen. I fired up the Onan in the driveway to run the roof airs and it quits. I went through the start cycle several times, same results. It wouldn't stay running as soon as it was about to accept an A/C load. This generator shut-down coincided with the convection oven L.E.D. panel flashing on momentarily. So off I go to the local Cummins folks figuring it was an Onan problem. Both generator start switches were doing their "three flash" indications, "Service Required," with a "27" error code. Cummins hooked the generator to their load bank and it ran great; volts, cycles all normal under max load. The load was disconnected and the generator quit. We did this several times with the same results. When you start the Onan with the wall thermostat in the air conditioning or fan position the A/C power comes on and runs perfectly under a load. When you turn the thermostat switch off, the Onan quits. I tried starting the generator with the convection oven door open so there would be just a very slight load with the small oven light coming on when the Onan was up to speed. The bloody thing ran like a champ. Of course when you close the oven door and the light goes out the Onan quits. Are we having fun now? For some reason the generator will not pick up the A/C load if it senses a very low load requirement, but loves to have a good load.

I suppose it could be one of three things: The Onan with one of its circuit boards that has a load sense function. The Xantrex inverter is Cummins' choice of being the culprit because if you open the inverter circuit breaker the generator will run until you close the breaker, then the generator will quit. I pointed out to the tech that the same thing happens when you start the Onan with its 35 amp breaker open, then when closing, the generator quits. The Cummins tech believes the Xantrex might have a programming problem, but even reverting to all the Xantrex default settings produced no change in operation. The last possibility is that the Surge Guard has a relay that is slow to close, and that confuses the generator load sensing; but that's stretching the point a bit. This Onan is definitely not going through a voltage surge according to the Surge Guard monitor panel; it is as smooth as can be as the generator goes through its 30 second run-up prior to supplying A/C power.

So, if there are any electrical wizards out there in Alpine Land, or possibly someone who might have experienced a similar problem; I would welcome any ideas you might have. Cummins' "real" electrician returns Monday from vacation and it would be nice to furnish him with as much information as possible.

Dick Bunting
2006, 36' FDTS
San Diego, CA

Birddog Pilot · 08-01-2008, 04:28 PM

Here's an interesting problem. I've been running the Onan once a month as prescribed with a good A/C load; in fact that was just done two days ago with no problem. Now today we bring the Alpine home to load it up for a three month trip, leaving tomorrow – not going to happen. I fired up the Onan in the driveway to run the roof airs and it quits. I went through the start cycle several times, same results. It wouldn't stay running as soon as it was about to accept an A/C load. This generator shut-down coincided with the convection oven L.E.D. panel flashing on momentarily. So off I go to the local Cummins folks figuring it was an Onan problem. Both generator start switches were doing their "three flash" indications, "Service Required," with a "27" error code. Cummins hooked the generator to their load bank and it ran great; volts, cycles all normal under max load. The load was disconnected and the generator quit. We did this several times with the same results. When you start the Onan with the wall thermostat in the air conditioning or fan position the A/C power comes on and runs perfectly under a load. When you turn the thermostat switch off, the Onan quits. I tried starting the generator with the convection oven door open so there would be just a very slight load with the small oven light coming on when the Onan was up to speed. The bloody thing ran like a champ. Of course when you close the oven door and the light goes out the Onan quits. Are we having fun now? For some reason the generator will not pick up the A/C load if it senses a very low load requirement, but loves to have a good load.

I suppose it could be one of three things: The Onan with one of its circuit boards that has a load sense function. The Xantrex inverter is Cummins' choice of being the culprit because if you open the inverter circuit breaker the generator will run until you close the breaker, then the generator will quit. I pointed out to the tech that the same thing happens when you start the Onan with its 35 amp breaker open, then when closing, the generator quits. The Cummins tech believes the Xantrex might have a programming problem, but even reverting to all the Xantrex default settings produced no change in operation. The last possibility is that the Surge Guard has a relay that is slow to close, and that confuses the generator load sensing; but that's stretching the point a bit. This Onan is definitely not going through a voltage surge according to the Surge Guard monitor panel; it is as smooth as can be as the generator goes through its 30 second run-up prior to supplying A/C power.

So, if there are any electrical wizards out there in Alpine Land, or possibly someone who might have experienced a similar problem; I would welcome any ideas you might have. Cummins' "real" electrician returns Monday from vacation and it would be nice to furnish him with as much information as possible.

Dick Bunting
2006, 36' FDTS
San Diego, CA

Wayne R · 08-01-2008, 05:09 PM

Check the junction box located above the generator. The wires tend to get pulled loose.

Rick Long · 08-01-2008, 06:21 PM

It sounds like you have a bad ground.. When you add another load your giving it a ground to use.

Also.. if your house batteries are down it will do simalar things.

Dale777 · 08-01-2008, 08:31 PM

Richard,

There are lots of posts on irv2.com about Onan genset issues, most of which are related to loose wiring either at the genset or at the coach. See this link for one of those issues that I had:

Code 27 on Genset

Also, do a FIND in irv2.com on "Onan" or "genset" or "generator" to find lots of comments on this subject.

Old Scout · 08-03-2008, 09:22 AM

There is a wealth of info on this site about Onans--old and new. With the older coaches (pre-2004), yr search was mostly limited to 1)loose wires in the junc box[es], 2) a poor ground, or 3) a dead cell in the house batteries. Post-2003, you can add in the Xantrex RS2000 software glitch [see other posts], Vansco comm boxes, Silverleaf interfaces, "Apex goblins", etc. Check out the Pre-2004 stuff first and hope its not a post 2003 issue....

Birddog Pilot · 08-03-2008, 03:06 PM

My thanks to all for the excellent suggestions. I did a topic search as suggested and sure enough, a wealth of information. At least, tomorrow, when I return to Cummins Cal Pacific here in El Cajon, CA, I'll be armed with some really great "past experiences," for the tech to consider.

Dick Bunting
2006, 36' FDTS

Renipladlo · 08-03-2008, 06:36 PM

Well, they are might be going to charge you to rewire the connections in the Genset junction box, since it's not a generator issue perse'. It takes a couple of hours max to fix it, and mostly all you do is make sure all "automatic" generator functions are disabled. Power to coach is disconnected, batteries are off, chassis switch is off. Inverter is disabled or off, charger is disabled or off.

extend the genset all the way out, put down the safety bar, wiggle you way into the compartment the generator occupies, take the cover off the junction box, do the rewiring of each wire at a time, strip off a little bit more insulation, use the correct sized wire nut (Blue) put the wires back together, put the wire nut on, tighten them real tight, put electrical tape over the nut/wire part, tuck that one back into the box, do the next one. There are four wires to do.

It will save you some money. Do the transfer/surge guard and inverter wiring check as well, and save yourself some more money.

This will save you lots of headaches down the road as well.

Good luck.

Birddog Pilot · 08-04-2008, 04:06 PM

Hi Monty, thanks again for the excellent synopsis of this problem and possible remedies. I spent most of the morning at Cummins Cal Pacific with the supervisor of their shop. Armed with all the pertinent information that I had gleaned from the "Forum" we both dove into the innards of the electrical system. Yes, all connections were good at the inverter, SurgeGuard (transfer relays), and J-box aft of the Onan. There were a couple kinks in the flexible coax leading from the gen to the J-box. We pulled it loose at both ends, removed the wire bundle, checked the wires, all okay, put it back together and relocated the clamp on the top of the Onan housing. Now when the gen slides in and out there is a nice relief loop that doesn't kink. The next step, while the main feed lead was disconnected at the J-box, was to run the generator; all was well. Then we disconnected the AGS input/output connector to inverter; everything was still good. With these two operations we figured the inverter had been isolated as well as the generator output. No problems encountered with everything reconnected. Problem solved? Well it looked like it. I came back later in the afternoon to pick up the coach, paid a very reasonable 2 hour labor bill and was ready to head for home. Oops, not so fast... One more test of the Onan, and it was back in its start-up, 30 sec. stabilization mode, and then for the switch to AC power – yup, the generator quit, the original problem all over again. More starts with the same results; back into the maintenance bay for more testing. The rotor/stator checked good so it now looks like a computer replacement tomorrow morning. Hopefully I'll have positive results to report tomorrow afternoon. By the way, the folks at Cummins couldn't have been more accommodating and pleasant throughout. I'm especially impressed with them letting me get in on all the action.

Dick Bunting
2006, 36' FDTS

takepride · 08-04-2008, 06:19 PM

Dick:

I sure hope you are able to document the problem, as I've had the exact same symptoms. The first time, it fried my Xantrex after the third restart. The second time it just started working fine on the second attempt. I turned off the load sensing on the Xantrex and since then, no problems.

Renipladlo · 08-04-2008, 08:30 PM

Dick, I keep hearing good things in General about Cummings/Onan service. My engine brake does not work, allison verified that the tranny is supposed to drop down to 4th, but, I don't think I am going to mess with it, simply it more trouble to bring it home, put it on blocks and work on it. We have a trip planned that will take us by Cummings Northwest in Chehalis, WA, so I will make an appointment for then, and let them check it out. There also might be some ECM upgrades needing to be done. They can do those as well. Hopefully it will be under warranty. Thank you for the thank you, keep us posted on the issue and its resolution please.

midflajim · 08-06-2008, 02:08 AM

If you haven't solved your problem WRV had a fix which required installing 2 additional relays. I had the same problem and this fixed it. I have the drawing from WRV and when I figure out how to post it I will

Jim& Kathy
06 Apex
Tampa fl

EngineerMike · 08-06-2008, 06:55 AM

Jim- This can go on the Alpine Tech Library page, as it appears to be a recurring issue. You can email Linda, the ACA webmistress, at the link at the bottom of that page, and attach a scan of the fix to your email. You may want to include your idea on how it should be posted; I would call this a House System, and maybe name the scan file according to the symptom & fix. Once it is up there, you can post a link to it on this thread. Thanks for sharing it.