Onan Fault Code 27

[a6carlos]

Hoping some of the experts here can help me narrow down my troubleshooting.

I have a 2014 Winnebago Vista 35F with an Onan HGJAB 5500 gas genset that just started throwing a Fault Code of 27. It seems the issue is with one side of the generated power, with the top circuit breaker causing the code 27. If I start the gen with both breakers off, I can turn on the lower one and everything is fine, but as soon as I flip the top breaker, the genset dies, doesn't matter which order the top breaker is turned on (first or second), always causes genset to die and pop code 27.

When I clear the code and try to start the genset with both CBs on, it immediately dies and pops the Code 27. When I start it with the top CB off, it starts and runs fine, but obviously no power since it is missing that leg from the stator.

We've had the same (top) CB pop once or twice over the last few years with the genset running but it reset easily each time. Bottom CB never popped (ever).

I've read quit a bit on this and other forums and feel it could be anything from a bad regulator to a bad inverter/converter or even a bad bearing or brushes, just looking for any advice from folks out there that might have seen the same problem before I dig in too deep.

[Old-Biscuit]

Here are 'service manuals' Part 1 & Part 2

Pg 44 (?) in Part 2 covers Fault Code 27

www.cleggind.com/postal_tech/pdfs/onan_srv_man_pt1.pdf
http://www.cleggind.com/postal_tech/..._man_part2.pdf

Like you said...could be dirty connection to magneto to stator

Have you swapped the CBs to see if issue follows (Top CB to Bottom CB)??

[a6carlos]

Thanks for the links.

I just swapped the CBs and same issue but now moved to the bottom CB. Switched them back and put a volt meter on it and get 120VAC from T3 and nothing from T1. T3 connected to top CB so when it is switched on, causes a spark and then genset shuts down. No power on lower CB so it doesn't cause any issues when turned on.

I think the next step is to take some more measurements to check voltages.

Anyone have the wiring diagram for the HGJAB?

[twinboat]

Have you confirmed, by disconnecting the leads to the transfer switch, that you don't have a dead short in the wiring leaving the generator ?

[Old-Biscuit]

Problem with top CB
Swapped CBs (top with bottom) and problem followed to 'bottom' CB ???

Have you replaced THAT CB?



Noticed that PART 1 of service manual LINK didn't work.
Here is new link
http://www.cleggind.com/postal_tech/...rv_man_pt1.pdf

Part 2 lists wiring diagrams BUT are NOT included.???

[a6carlos]

Originally Posted by twinboat

Have you confirmed, by disconnecting the leads to the transfer switch, that you don't have a dead short in the wiring leaving the generator ?

Thanks for the suggestion, I have not gotten that far yet when the rain came while troubleshooting so I had to pack it in for the day.

[a6carlos]

Originally Posted by Old-Biscuit

Problem with top CB
Swapped CBs (top with bottom) and problem followed to 'bottom' CB ???

Have you replaced THAT CB?



Noticed that PART 1 of service manual LINK didn't work.
Here is new link
http://www.cleggind.com/postal_tech/...rv_man_pt1.pdf

Part 2 lists wiring diagrams BUT are NOT included.???

Thanks for the updated link. The wiring diagrams are listed in the table of contents as appendices but neither Part 1 nor Part 2 had the appendices in them but I was able to find the schematics on the cleggind.com website by altering the link above to get to the Postal Vehicle main page.

As for the CB, I'm making the assumption that they are good since the problem shifted from the top one to the bottom one when I shifted the wiring. With T3 producing 120VAC and T1 producing nothing (both pre CB measurements) it seems to me the problem is occurring before the CBs.

Am I making the wrong assumption?

[Old-Biscuit]

Originally Posted by a6carlos

Thanks for the updated link. The wiring diagrams are listed in the table of contents as appendices but neither Part 1 nor Part 2 had the appendices in them but I was able to find the schematics on the cleggind.com website by altering the link above to get to the Postal Vehicle main page.

As for the CB, I'm making the assumption that they are good since the problem shifted from the top one to the bottom one when I shifted the wiring. With T3 producing 120VAC and T1 producing nothing (both pre CB measurements) it seems to me the problem is occurring before the CBs.

Am I making the wrong assumption?

OK...following you NOW

You didn't swap 'CB' (top to bottom) you swapped 'Wiring' T1/T3

T3 was on top CB..then swapped it to bottom CB and same issue
T3 is source of problem
Need to do a resistance test
Good luck.....'


Generator Testing PG. 36
https://www.manualslib.com/manual/82...b.html?page=36

[a6carlos]

OK, after a weeklong business trip that kept me away from the RV but gave me some time to think about possible sources of the problem, I was able to solve the problem yesterday.

It turns out it was a chaffed wire (CB2) coming out of the genset and feeding the transfer switch. The chaffing occurred right as the wires are leaving the genset in the sealtight connector coming out of the bottom of the genset. Before entering the sealtight connector, they come out of the control panel (and off of the CBs that kept popping) and go through a rubber "plenum" which allows for flex between the genset frame and the generator itself.

Apparently, the black and yellow "CB2" wire had been free enough to rub on either the locknut on the sealtight connector or on something else nearby. It rubbed enough to get to the copper which then shorted to ground whenever the generator applied 120VAC to CB2. This caused the genset control board to shut down the power on that leg and gave the resultant "Fault 27."

The repair was a couple of well placed pieces of shrink wrap as well as protecting the entire wire bundle coming out of the sealtight connecter with rubber, friction, and finally black electrical tape. I wanted to replace the entire wire but found it too be a bit too much of a challenge due to the lack of space in the sealtight. I'll check on the repair after a couple of trips but if I see anything strange from the genset, I'll know where to start!

Thanks to all for the help in troubleshooting, I am now way too informed on how the Onan works and how the power is transmitted throughout the coach.