Onan 4000 just shuts down on load No tripped breakers

Interesting thread. I just experienced this exact thing today with my gen shutting down running a single AC unit and nothing else. About 105 deg today so I did not know if I was having a problem with a fuel line getting vaper-locked - that is what is acted like when it shut down, and it would not re-start until some time had passed. It still should not be shutting off like this running only the AC on low fan... I will try again tomorrow and check the codes. For the record - my gen shows over 1000 hours but seems to run well and smoothly right up to where it shuts off.
This is my first rig with a gen so new territory for me. I also was not aware that there were fault codes or where to look for them. Thanks for the info! This rig came with no manuals or documentation so the interweb has been getting abused...

Just checked the faults - I had 33 and 36. Not sure on coolant on my 2002 4K - I will have to look and see, but I assumed it was air cooled. #6 is Engine stopped but not commanded to stop. Not sure on this one as I just filled above 1/2 tank and there should not be any issue picking up fuel. Unit will run forever with the ac off, and the ac seems to run correctly and not laboring. I can run it off a 15 amp circuit at home without a breaker tripping, but the cord does get warm. I guess I need to get familiar with this thing....

I did the flashing code check, and it was a 3 and secondarily a 15. It is an overload problem as we thought. I'm going to try the Supco Hard Start kit and see if we can get a little more out of the generator. Ultimately I'd like to be able to run two Mach 3 PS high efficiency ACs at the same time. They draw just a little over 10 amps running. I hope having one running already then starting the second won't shut down the generator. Running a hair dryer and microwave is mimicking the one AC running and trying to start a second. I really hope it works because going down the road with the one AC in hot weather doesn't cut it.

Howdy, my 2002 Winnebago mini has a sign on the microwave that says:
DO no use the microwave and AC while running on generator power.

I have always believed those 2 can not run at the same time with a 4k generator

Thanks for the link. I'll see if I can find the codes. I didn't know the light did that.

Have you checked what 'Fault Code' is being indicated at time of shutdown?

Fault Codes
The genset controller provides extensive diagnostics by causing the status indicator light on the Control Switch to blink in a coded fashion.
Following a fault shutdown, the indicator light will repeatedly blink one, two, three or four blinks at a time.
• One blink
indicates shutdown due to high engine coolant temperature.

• Two blinks
indicates a low oil pressure fault.

• Three blinks
indicates a service fault.
Press Stop once to cause the two-digit, second-level fault code to blink. (Pressing Stop again will stop the blinking.)
The two-digit code consists of 1, 2, 3, 4 or 5 blinks, a brief pause,
and then 1 to 9 blinks.
The first set of blinks represents the tens digit and the second set of blinks the units digit of the fault code number.
For example, Fault Code No. 36 appears as:
blink-blink-blink—pause—blink-blink-blink-blink-blink-blink— long pause—
repeat

• Four blinks
indicates that cranking exceeded 30 seconds without the engine starting

Here is a Troubleshooting Guide that has other indicators PLUS second Level Faults

LINK

DO some Troubleshooting.......

Here is a manual I found on the Onan website.

I am not familiar with the 4000 but have owned a 5500 and a 7000.

Both have electronic voltage regulators that control the frequency and voltage. If either get out of spec either from load or a mechanical issue it will shut the generator off to protect it.

I am pretty sure yours has this too.

I am pretty sure you can get fault codes from it too that will probably tell you why it shut down.

Happy reading.

You could also take it to a service center and demonstrate it.

Sounds like you are overloading it to me. With the ac on I would not try to run anything except lights and one other thing.

Need to know what you have.

Thanks for the replies. So, if I understand correctly at startup the AC draws enough to exceed the amp capacity of the generator. So rather than tripping a breaker, the generator apparently has some mechanism that shuts it down. That's what I'm wondering about: does it have such a mechanism (and apparently it does from what has been said here) and what is it and where is it? Would a hard start capacitor on the AC help? For when the generator quits is when an AC starts and some combination of appliances are already working, the total running amps though never is more than 21 or 22.

DirtyOil wrote:

marcsbigfoot20b27 wrote:

howardwheeler wrote:
We've checked what we know and find nothing amiss that's obvious. But if we have the microwave and a 1200 watt hair dryer going and the AC kicks on, the generator just stops. But no circuit breakers ever trip. I find nothing in the manual that says the generator just shuts down by itself if 20 to 25 amps are being drawn. I wonder if a fuel filter could be constricted just enough that when the governor calls for full throttle, it starves for gas. Do you think that's a possibility?

1200 watts hair dryer
1200 watts microwave input or more
1800 watts AC start up draw or more
4200 or more watts???

X2 overloaded.

X3 - with our last coach, we used to have a rule only 2 of the following 3 on at once.
1 - hair dryer
2 - microwave
3 - AC

marcsbigfoot20b27 wrote:

howardwheeler wrote:
We've checked what we know and find nothing amiss that's obvious. But if we have the microwave and a 1200 watt hair dryer going and the AC kicks on, the generator just stops. But no circuit breakers ever trip. I find nothing in the manual that says the generator just shuts down by itself if 20 to 25 amps are being drawn. I wonder if a fuel filter could be constricted just enough that when the governor calls for full throttle, it starves for gas. Do you think that's a possibility?

1200 watts hair dryer
1200 watts microwave input or more
1800 watts AC start up draw or more
4200 or more watts???

X2 overloaded.