Error code 35 on Onan generator

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Ohiosnowbird

Well-known member
Joined
May 19, 2023
Posts
348
Location
Ohio
Hi it’s us with the cursed camper….the generator is throwing a code 35, which in reading, means control panel error take it to the dealer. Our dealer is in Huntsville, we’re in Ohio. We just don’t trust anyone to do a repair with everything else that has gone wrong. We wanted to leave January 1. Do you guys know anything we can try before taking it for repair? Any ideas appreciated.

QG4000
4KY-26100R model number
it has 1152 hours
 
What are the symptoms. (Does it crank? Does it start then die? How did the problem first present?)

If you can’t get diy repair direction here, I imagine you could take it to any Owen’s Cummins shop for warranty work… I would trust them over an RV dealership.
Thanks. Symptoms: We hit the start button, it starts just fine, then revs high, then cuts out.
 
The data sheet I found for the QG series of 4K gensets shows it has a carb. That implies it's controlled by a governor and an over-rev condition would be mechanical. So my first stab at it would be to check the carb, governor and choke linkage for something binding or otherwise discombobulated. You may find something simple/stupid that obviates a repair detour.

Mark B.
Albuquerque, NM
 
Thanks. Symptoms: We hit the start button, it starts just fine, then revs high, then cuts out.
We had ours serviced once at a Camping World (lesson learned). Part of what they did was change the fuel filter. Afterwards it would start, run for maybe 3 seconds, then shut off. I don’t recall the error code, but it was as vague and unhelpful as yours.
Took it to an Onan Cummins shop. Turns out, CW didn’t purge the air in the fuel filter. The fix? Hold the prime down for a couple of minutes (one time to purge the air… after the one time, it started as it always had).
Hope your fix is as simple and painless as that.
 
We had ours serviced once at a Camping World (lesson learned). Part of what they did was change the fuel filter. Afterwards it would start, run for maybe 3 seconds, then shut off. I don’t recall the error code, but it was as vague and unhelpful as yours.
Took it to an Onan Cummins shop. Turns out, CW didn’t purge the air in the fuel filter. The fix? Hold the prime down for a couple of minutes (one time to purge the air… after the one time, it started as it always had).
Hope your fix is as simple and painless as that.
Thanks. We went out and tried that. Nope. I wish it had been that simple!
 
The data sheet I found for the QG series of 4K gensets shows it has a carb. That implies it's controlled by a governor and an over-rev condition would be mechanical. So my first stab at it would be to check the carb, governor and choke linkage for something binding or otherwise discombobulated. You may find something simple/stupid that obviates a repair detour.

Mark B.
Albuquerque, NM
Thanks. We’ll look at your suggestions today.
 
Have you seen and read this? But I would still look for obvious problems, such as bad or dirty connections, low voltages, etc, before blaming the control board.

-Don- Reno, NV
Thanks! Wow, this is great. When hubby gets up I’ll show it to him. He’s kind of bummed and I’m letting him sleep in a little, just a little! Thanks again.
 
Revisiting this issue.

We’ve done everything suggested here. We replaced the air filter, cleaned linkages, carb. Nothing. Same result.

In this issue we found a great repair guy, older with a good deal of experience, who suggested everything you guys did, we went to him (a cummins shop) to get a new air filter. He also suggested to just disconnect the control, leave it sit a bit (to reset) then reconnect. Apparently we’ve learned, the original Onan control panel, made in China and very expensive to replace, is known for failure. Rare at 1152 hours according to our new repair guy. Cursed camper, what can I say? The control panel made in America, an aftermarket part, is the one to use in replacement. Our logic is to just replace it. We’ll be ordering it Monday.
 
I think there is an error in human communications here.

Your problem is NOT the control panel, but the control board.

The control board is located inside the generator.

-Don- Reno, NV
Yes, you’re right. Error in the wording I chose. We’re getting a new control board from Flightsystems.
 
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To continue this. We replaced the control board we obtained from flightsystems it doesn’t shut the generator down like the original Onan (which probably means the other control board was fine) and now the generator runs too high rpm constantly. We’re thinking carburetor. We’ve cleaned the throttle linkage and choke linkage and no change. We cleaned the carburetor as well. We’ve been using one of our honda generators while we’re home and I guess we’ll leave Jan 1 without the Onan working, (being newbcakes we have full hook up everywhere) unless someone has any other ideas?
 
Will it not adjust RPMs? Is it giving an error code 14?

You probably already have the hardware fixed; it now probably only needs an adjustment.

-Don- Auburn, CA
Hubby is unaware of how to adjust. He says he’s a builder and an accidental mechanic (he works on all of our farm equipment) and is stumped by this one. How do you adjust? Not afraid to try, just don’t know how. Thanks!
 
Hubby is unaware of how to adjust.
Is it starting and dying in a few seconds, giving error code 14?

First, find the linkage that goes the carburetor. You will see a couple of adjustment screws on the far end of the linkage (away from the carburetor) you can play around with. You should be able to slow it down there and see if it then works and no longer dies. Since it is not working now, you have nothing to lose by trying.

Then we can find a correct procedure in the service manual. But you may not need it, if it all works and tested under various loads to no longer dies.

It is helpful to have something like this to know when it is at 60 hz.

-Don- Auburn, CA
 
Is it starting and dying in a few seconds, giving error code 14?
Thanks.
The new control board does not throw error codes (it’s not an Onan original, we got a new Flightsystems, USA made). The old control board threw a code 35 and shut the generator down. The new control board allows the generator to keep running instead of throwing error codes. It’s running (loudly) at a dangerous rpm. It is working. Hubby is going to try what you suggested tomorrow to adjust.
 
The new control board allows the generator to keep running instead of throwing error codes.
I had no idea the after-market control board wouldn't show the error codes.

Get a frequency meter or Kill-0-Watt meter and get the genny adjusted down to 60 hz and see how that works. Check cold and hot, should always be between around 57 to 63 hz regardless of temperature, loads, etc.

From there, if there are still issues, with intermittently dying, or not being close to 60 hz when the loads change, we can find the correct procedure in the Onan Service manual. But there is a good chance you will get it working fine just by playing around with the adjustments under various loads, temps, etc.

First, simply slow it down.

-Don- Auburn, CA
 
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