Onan 4000 Generator or A/C Issue? 2010 Access 31J

[Ranger-WO]

On a recent trip I've been having problems with the generator quitting. It first happened while driving with the generator on and the A/C running. Everything worked the first day. On the second day, the generator would quit while driving but would run while stationary. Yesterday it would quit even while stationary.

Before it quits, it sounds like a heavy load is being applied. Sometimes it shuts down, other times it has recovered and run normally. This happens only when the A/C is running, but not when the A/C starts up.

The error code it shows is 1-3 for low voltage. The only items running were the A/C and converter, so too high of a load does not seem likely.

Generator is an Onan 4000 (gas) with about 750 hours (30 hours recently). It's worked well for the 3 years I've owned it.

A/C is a Coleman Mach 10 15000 Btu. It does NOT have a soft start. I cleaned it about a month ago and it seems to work well on shore power, though we did have a breaker (30A) trip at the power post at a campground on the trip. However, we had the A/C, water heater, ice maker etc. running at the time, so the load may have been too high.

What suggestions do you have on next steps?
Should I be looking at the generator or the A/C?
I'm pretty mechanically inclined but don't have much experience with the electrical aspects of generators.

Thanks!

 

[Morich]

I don't think it will be a load problem but I lean toward possible fuel flow?
What about a filter beginning to clog? If it has not been changed, that might be a first start.
Your comment about more prone to fail while driving, seems like maybe the engine and genset both wanting fuel the genset may be starving out?
But if you feel the filter is good, possible fuel pump beginning to go?

I'm not too high on some of the error codes as it can show low voltage but that may happen just as the engine slows down to quit if it is being fuel starved!

But those ARE totally based on my "theory" without much to back it!

 

[BCam]

I think Richard's on the right track. Check out this thread from IRV2.com:

https://www.irv2.com/forums/f258/generator-quiting-under-load-348340.html

 

[Ranger-WO]

I went ahead and replaced the filter and the pump. I ordered them when things started acting up, so already had them on hand. It ran for about 15 or 20 minutes and quit again. However, this time I noticed that the A/C compressor stopped for a few seconds, then started to come back on. Then the generator bogged down and stopped. It was pretty hot inside at the time and well above the set point. Any ideas why it would turn off and back on again so quickly?

While replacing the pump, I also noticed a small leak near the carb bowl, so that's something else I'll have to get fixed. Not sure exactly where it is leaking yet.

Thanks!

 

[Morich]

Well, that does throw the doors wide open on possible solutions/fixes!
The possible fuel leak is still a definite question as fuel flow needs to be steady but the compressor stopping might be a different problem and possibly put it over into electrical?

That electrical can be lots of different things starting at the thermostat, through wiring and up to wiring in the rooftop. Any number of connections along the route that rattle around to lose contact may make the compressor stop.
That stop and sudden restart may be major item as there should be a time delay on many systems to let the high pressure reduce before a restart.
Restarting the compressor when there is high pressure can often be enough to blow breakers and not a good thing at all for the life of the AC!

One shotgun approach that I might look over is just checking the electrical connections for being tight. I'm not a trained guy for air work but I can tell if a connection is getting loose.
Pulling the cover on the thermostat might be a first thought as that is where the signal starts and a loose wire there could be easy enough to find? also there are often connections between the tail on the thermostat wiring and where that part meets the Winnebago wiring. That factory portion may be 8-10 inches long with the connections pushed back down into the wall, so try pulling it a bit to see if those connections in the wall are good?
But not to panic if you don't find any because that can vary and some have none there.

RV bounce around so much that it is not bad to just go through to look for things getting loose!

 

[creativepart]

When Rooftop RV A/C fail or begin to the refrigerant line many times springs a small pinhole leak. Over a short period of time that refrigerant leaks out the pinhole and tacked all the compressor’s oil with it. When this happens the compressor bogs down and the number of amps required to run it increases many times the normal amount. Eventually, it will fail completely.

So that “could” be the issue.

Or it could be your generator not being able to respond to the large amp requirements of your A/C startup.

So, that could be the issue. Or it could be both things.

An independent mobile RV tech could quickly check your A/C’s amp draw to determine if that’s the issue. And they could also check out the generator operation, too.

By the way, getting an OEM Onan generator carb is really hit or miss difficult. And Amazon and others sell “compatible” replacement carbs that are known to not work well or sometimes not at all.

 

[BCam]

Or it could be your generator not being able to respond to the large amp requirements of your A/C startup.

You could take your A/C out out of the equation by trying your generator with similar amp draws and see how it performs? I couldn't find anything specific but I did see an unofficial reference to 24.5 amps (2,940 watts at 120V).

 

[Ranger-WO]

I went back and tried to confirm what I thought I heard with the A/C compressor stopping and suddenly restarting. I've not been able to get that to reoccur, so I'm now in doubt about what I heard. However, the generator did quit again without the A/C compressor shutting down.

That being said I'm leaning toward a fuel flow problem. Since there is a small leak around the carburetor (can't tell exactly where, but most likely the bowl gasket or around the altitude adjustment), I am planning to start there and see where it takes me. Regardless of that being the problem causing it to quit, I don't want fuel dripping.

I will also try putting on a load similar to the A/C in order to see if I can recrate the failure and eliminate the A/C as the issue.

I'm hoping I don't have to go as far as replacing the carb. I will avoid the Amazon ones, so thanks for that advice.

I'll post a follow up after I've had a chance to work on it this weekend.

Thanks!

 

[keithd311]

A couple of other things that might help. On my 2004 29b, there is a rubber fuel line that connects from the top of the gas tank and then to the metal fuel line that goes up to where the Onan sits. This line on my had cracked due to age and was letting air into the fuel line that would cause the generator to fail since it was getting too much air in the gas line.
Second thing is making sure the Onan is running at the right RPM. You can check this by looking at the frequency being produced by the generator with and without load. Without load the frequency should be like 63 per 64 Hz - the actual number is in the manual for your version of the Onan. Mine was around 60 without load and adjusting that helped.

 

[powercat_ras]

I have a 2014 vintage Onan 4000 gas powered in my RV. I had issues with it shutting down under load due to overheating. There's no specific fault code for this. Even so there seems to be a temp sensor somewhere that the control board monitors that lets it decide to do a shutdown for this reason.

If I remember right, it would store code 36 when it shut down due to overheating.

Some causes can be:

1. The side cover has to be on for the air cooling to move air over the generator and engine.

2. On my RV, part of the hot air that exhausts out the bottom to air cool the engine was being sucked into the air intake vents on the side cover, causing the inlet air to be much hotter than ambient temperature. If your RV has an access door on the side try leaving it open and see if it still shuts down. If not you may have a similar issue.

On my RV, I modified a rectangular to round HVAC duct adapter to extend the hot air exhaust downward so that the hot air exhausted farther away from the intake and below the level of the RV sidewalls. Have had no unexpected generator shutdown problems ever since.

 

[Bobn1957]

On a recent trip I've been having problems with the generator quitting. It first happened while driving with the generator on and the A/C running. Everything worked the first day. On the second day, the generator would quit while driving but would run while stationary. Yesterday it would quit even while stationary.

Before it quits, it sounds like a heavy load is being applied. Sometimes it shuts down, other times it has recovered and run normally. This happens only when the A/C is running, but not when the A/C starts up.

The error code it shows is 1-3 for low voltage. The only items running were the A/C and converter, so too high of a load does not seem likely.

Generator is an Onan 4000 (gas) with about 750 hours (30 hours recently). It's worked well for the 3 years I've owned it.

A/C is a Coleman Mach 10 15000 Btu. It does NOT have a soft start. I cleaned it about a month ago and it seems to work well on shore power, though we did have a breaker (30A) trip at the power post at a campground on the trip. However, we had the A/C, water heater, ice maker etc. running at the time, so the load may have been too high.

What suggestions do you have on next steps?
Should I be looking at the generator or the A/C?
I'm pretty mechanically inclined but don't have much experience with the electrical aspects of generators.

Thanks!

One thing that no one has mentioned is the fuel level in the tank, the generator doesn't draw fuel from the bottom of the tank, so you don't run out of fuel for the chassis, if your fuel level is at that point the gen will draw air and cause it to stop!