Onan 4000 main breaker constant trip

[Motorosi]

Hello guys-
Onan4k. Start the gen with all breakers off inside. Breaker off outside (on the gen) and she starts fine, I flip the outside breaker on and immediately she powers down. Like a safe mode. I unplug the only plug I see on top of the board going out to the rv itself. Same problem. I slide out the plate with the breaker on it. No pinched wires. The white wire coming in has 120v. I believe 60HTZ. Now the black wire going out is my problem. I unplug that from the other side of the breaker. All is fine. Obviously. Breaker on/off. All good. No power. Turn off. Plug back on, back to step one. I changed the breaker. Same problem. I try to trace that wire, goes by Nader the board. I didn’t remove the board. Don’t want to damage it. Shore power works fine. I’m missing something here.
Thanks in advance friends.
Craig

[hilgert]

First, welcome!!!

Second, *please* create a signature with your RV year, make and model. That way folks with similar RVs might chime in with similar issues. You can create a signature here:
https://www.irv2.com/forums/profile....=editsignature

Third, your problem. Sounds to me like the generator has no issues...it sounds like there is something else going on downstream in the RV. Did you have shore power disconnected when you tried the generator? If shore power was not disconnected, please disconnect and try the generator again and report back with results.

[Motorosi]

Copy. Doing all that now.
This is a 2019 Forest River 20cb. Ford transit chassis.

I had NO shore power connected. I have pics and videos. Let me see if I can upload. If not in the gen, then that black wire coming out of the breaker is the culprit. But it goes under the board to the left. Or inside it.

[hilgert]

Originally Posted by Motorosi

...
I slide out the plate with the breaker on it. No pinched wires. The white wire coming in has 120v. I believe 60HTZ. Now the black wire going out is my problem. I unplug that from the other side of the breaker. All is fine.
...

When the generator shuts down it should remember the fault code, which will be displayed on the generator via the blinking light on the start/stop switch. Look in your Onan manual (or find online) for Troubleshooting, and it will tell you how to read the codes (you count the first set of blinks, then the second set of blinks), which tells you the code. This will help diagnose the issue.

I am suspecting this might be an issue with your ATS (automatic transfer switch), but that's a wild guess at this point not yet knowing the fault code.

[twinboat]

Look for a juntion box near the generator. Some have wire nuts that fall off and short.

A Onan generator will automaticly shut down if it detects a shore circuit.

[Motorosi]

Nothing next to the gen. Goes straight to the panel inside. I’ll upload a picture. Fault code 27.

[Motorosi]

[hilgert]

From somewhere online...

Code 27 - Voltage Sense Error
What this fault code tells you is that the controller cannot sense the output voltage. Again, this problem may be beyond your expertise to repair. The manual states that the only solution is to go to your authorized Onan dealer to rectify the issue.

Motorosi, in the picture (below) the connector does not look like it's fully connected...I'm hoping you had just removed it and had not yet reinserted it when the picture was taken???

[Motorosi]

Yes. Exactly right. I was separating the gen from the rv completely. See if the breaker would stay on. No luck.

[Motorosi]

That black wire coming out of the breaker is the problem. I disconnect that and the gen runs with the breaker on or off.That’s the feed out of the breaker. I tried tracing it, it’s in a split loom tubing by itself and goes under the control board to the left. Does not come out of the gen. I’m assuming one of those wires in that plug is carrying the power? Only mother wire in a gray conduit is a orange Romex all the way to that box (in picture) on top of the panel in the rv.

[hilgert]

Google "Onan fault code 27" and you'll find lots of links with some potential causes/solutions (some not requiring an Onan service facility).

Here is one example (on this forum in fact) where the cause was a chafed wire, solved with some wire shrink wrap (see last post):

https://www.irv2.com/forums/f54/onan...-a-358175.html

.

[Motorosi]

Let me check that out. I appreciate it. Sorry for the typos. In the heat with this small phone phone my wife got me. Lol.

I kinda want to lift the board up and take a peek. Never messed with one before.

[1972VWbus]

Either the circuit breaker itself needs replacing or the voltage regulator.