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Old 06-15-2019, 04:35 PM   #1
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THOR #12484
Onan 4K generator shuts off

Hello all. I have a 2018 Vegas 24.1. After finally boondocking for a week I discovered the generator would shut off and not restart for 20-60 minutes.
Trouble shooting reveals it shuts off when the AC thermostat reaches the set temp and the compressor stops. I tried this at various thermostat temps and it verified.
Any ideas on what I can do to avoid this issue?
Thanks
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Old 06-16-2019, 03:07 AM   #2
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THOR #2631
"Basic" thermostats which call for cooling should also include a built in time delay (typically only for several minutes) that prevent starting the A/C compressor immediately. This (one reason) is mainly to prevent short cycling the compressor which can be damaged if head pressure is not bled off from a previous cooling cycle, before the next cooling cycle starts. When you say 20-60 min delays before the gen will restart....do you mean there is a call for cooling again, and the gen cranks but wont start until it cools down for 20 to 60 minutes......or do you mean the thermostat or AGS system does not call for a restart for 20-60 minutes?
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Old 06-16-2019, 03:22 AM   #3
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THOR #12484
Thanks for the response. Not an auto start generator. Manual start that happens to die when the AC reaches set temp and compressor stops. A surge problem? Reading recently about a possible idle control problem as well
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Old 06-16-2019, 03:37 AM   #4
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OK, so interesting that the gen shut down seems to be linked to the thermostat cooling set point being reached......is this a Dometic digital thermostat?
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Old 06-16-2019, 04:00 AM   #5
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THOR #12484
It is a digital thermostat but no Dometic but shouldnít have any wiring relationship with the generator.
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Old 06-16-2019, 04:52 AM   #6
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I was still thinking AGS and Dometic thermo control.......but no AGS; no Dometic. So gen basically dies when the air conditioner reaches set point temp (compressor shuts off). The compressor shut off should create a sudden current drop and simultaneous AC voltage increase on the gen output.......so perhaps the gen control board is responding (for some reason) with a shutdown, but normally that should not be an issue. Any fail codes created with this shutdown at the generator?
Short cycling the compressor (if it tries to restart very quickly after just turning off) could create very high AC load currents, which you would think would trip either the gen breaker or the air conditioning breaker. Since that is not happening short cycling probably not happening either. Just thinking out loud here.
The other strange issue is the 20-60 minute time to be able to manually restart the gen. When the gen stops the transfer switch should disconnect and transfer back to shore connections (even if you are boondocking), so trying to restart the gen should be easy since it would be unloaded. If the transfer switch is not switching off the gen output feed then perhaps the gen is trying to restart under load? This is a stretch, but turn off air cond and converter and try to restart the gen after one of these air conditioning compressor temp reached cycles. If the gen still does not start there must be a gen issue perhaps resulting from being hot and trying to restart......nothing to do with the air conditioning other than being a 1.5kw load on the gen. So flakey fuel pump etc. ? What happens if you just start and run the gen with no air conditioning at all until the gen is hot and then shut off manually......does it restart without issue?

Time to grab my "beauty sleep"......some more thinking and testing things required on this one.
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Old 06-16-2019, 11:13 AM   #7
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THOR #12751
When you say it takes 20 - 60 minutes until you can restart the gen.... does it crank and not start or won't it even crank? How long has the AC been running before it shuts off?

A couple things I can think of to consider....

1) Possible heat issue. The AC is probably the biggest current draw so perhaps the load is causing the generator to get too hot causing the shut down and then it has to cool off to restart. Might be worth checking that the cover is on the generator is tightly sealed for proper air flow and cooling for the generator.

2) My generator will not run when the gas tank hits 1/4 full. Maybe a grounding issue is causing a false fuel level signal to be sent when the AC shuts off.

Definitely a strange one....
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Old 06-16-2019, 11:54 AM   #8
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THOR #4735
from experience, the generator will have no correlation with the roof a/c unit's thermostat, or the interior temperature, or anything to do with anything other than the generator's own capabilities - if it is shutting down, then it is due to either a manual 'off' of the switch, or a overheating situation, which should also render a flashing 'code' on the interior switch. Since the gen won't start for quite a while, it certainly sounds like overheating and a cool down period is required. The 'code' will reveal this, as it has happened to my own QD6000, and the Onan customer service said that this 'cool down' period is required before the gen will restart.

When you are running the roof air, and possibly other things like the battery charger, electric water heater, and various 120v devices, all at once, during hot weather conditions, and especially while PARKED, with little air movement, the generator, which is an engine that needs air flow to keep it cool, can certainly have times when it will overheat.
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Old 06-16-2019, 12:36 PM   #9
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Quote:
Originally Posted by mstng View Post
It is a digital thermostat but no Dometic but shouldn’t have any wiring relationship with the generator.
When I purchased a digital thermostat and installed it in my Axis, everything ran fine. I put in a small switch to be able to run the fan at both low and high speed. A year later, I had an issue with my furnace that I thought might be associated with the thermostat so I switched back to the original one. It turned out not to have anything to do with the thermostat. When I reinstalled the digital thermostat, I decided not to keep the hi/low fan switch, since I always ran the fan on high. Instructions on the internet for installation of the digital thermostat said that I could combine the high and low fan switch wires instead of running them thru a switch. After that, when I ran the A/C on shore power, the A/C would cool down until the compressor shut off and then the compressor would cycle off and on and never cool the coach down to the temp setting on the thermostat. When I tried to run the A/C off the generator, it would run for a while and then the generator would slow down, the voltage would drop and the generator would finally die. Couldn’t figure it out so called in a technician who figured it out in a heartbeat. Turns out the internet instructions were wrong. Putting the high/low fan wires together “confused” the module which controls the A/C located in the unit above the couch. When he separated the two wires and only connected the “high” fan, everything including the generator worked fine. It might be worth a try to switch back to your original thermostat (if you still have it) and see if that fixes the problem.
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Old 06-16-2019, 02:37 PM   #10
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THOR #12484
This is such a terrific forum. Thanks for all your ideas and suggestions.

This is a digital thermostat that I installed and left the extra wire taped. (I think)

It was a very warm week and I was running it for several hours at an amusement park in the hot sun. The 20-60 minutes varies and as some of you suggest it may have something to due with over heating. Wouldn't I expect if this was the cause that it would happen randomly instead of when the compressors cycles off? It also happened on the trip home while underway.

It has only 75 hours, fresh gas and I changed oil at 50 hours. Perhaps the air filter as it's was running in a dusty parking lot. Then again, why when the compressor cycles off?

I need to research how to check for codes.

Thanks again, ill keep at it..

Bill
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Old 06-16-2019, 04:31 PM   #11
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Troubleshooting continued this morning. Couldn't get the generator to start from the remote wall switch or the dash switch. Coach is on, batteries fully charged, everything else works. No action from either switch. Implications?

Tried the generator manual switch and it cranks and ran fine for no more than 10 minutes unrelated to temp thermostat (Turned off before compressor cycled). Tried that twice. Also seems unrelated to over heating.

Currently running with no load and will see how that goes.
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Old 06-16-2019, 05:08 PM   #12
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THOR #1765
If it runs with no load without any problems, try putting as much of a load as you can on it without turning on the A/C.
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Old 06-17-2019, 02:41 AM   #13
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Originally Posted by mstng View Post
Troubleshooting continued this morning. Couldn't get the generator to start from the remote wall switch or the dash switch. Coach is on, batteries fully charged, everything else works. No action from either switch. Implications?

Tried the generator manual switch and it cranks and ran fine for no more than 10 minutes unrelated to temp thermostat (Turned off before compressor cycled). Tried that twice. Also seems unrelated to over heating.

Currently running with no load and will see how that goes.

Glad you are trying to resolve your strange gen no start issue(s). So in the morning (gen is cold) you had no problem starting from the prime/stop/start button on the generator........but you say you could not start from either remote prime/stop/start button. Do you mean no cranking at all; or cranked OK, but no start? Since both remote switches fail to do their job.....look for a common fault where the remote y cable connects to the local switch at the generator......might be a loose connection; loose pin in a connector; bad termination; broken wire etc.
Regarding the codes set when the gen fails on your overheat; or coincidental compressor turn off trouble. Check the Onan Operator manual for the gen you have and I think you will find how to determine the code being set (Section 4 in my KY) and I believe you can even recall the last code set (may be dependent on gen model though). On older class A coaches with gen mounted near the front (close to the engine/exhaust etc.) there have been many complaints about gens shutting off and hard to restart due to heat and poor cooling/ventilation of the gen; and all that goes with it.....vapour lock; fuel pump failures; gen over temp shutdown, etc. Hopefully you will be able to obtain an associated code for your recent fault.
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Old 06-23-2019, 12:20 AM   #14
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THOR #12484
Hello guys, an update.
Back at it with the generator. Very hot day with temps close to 100 and unbearable humidity. Almost convinced that over heating must play a part as suggested in generator shutting off. Pulled some oil off down from the full mark to the add mark and its been running for over 2 hours with AC cycling on and off, no surges and no stopping. Whether this is coincidence or truly helped I have no idea. It was recommended elsewhere and some of you may have some insight to that. Time will tell if truly fixed.
Why it would start from the generator start switch but not from the cab switches I don't know. Low voltage perhaps? Cables are secured. It's fine now but has been plugged in for a week.

Thanks for your thoughts.
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Old 06-24-2019, 12:30 PM   #15
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THOR #5597
I had the same problem with the generator in our Jayco Alante 26AY. It would shut down after running foe a while. When I changed the oil, I left the oil a little low and the problem went away.
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Old 06-24-2019, 12:58 PM   #16
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Possible solution but I'm no electrician. IF your generator is an inverter style, it will throttle back once the load is reduced. Can it be possible that, whatever sends this "throttle back" pulse/signal to the generator, could be (for lack of proper explanation) sending back too strong of a signal or something along that line. One of these "electrical brainiacs" we love so much on this forum can probably explain this or dissect it enough to tell if this could be the interference.
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Old 06-24-2019, 01:37 PM   #17
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Thanks Gritz Carlton. Thatís exactly what was happening. Load reduced (AC cycled off) sputtering for a second and generator shuts down. Not sure what inverter style means but definitely the generator normally cycles up or down when loaded or unloaded. Time will tell if reducing oil helped.
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Old 06-24-2019, 01:41 PM   #18
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Originally Posted by mstng View Post
Thanks Gritz Carlton. That’s exactly what was happening. Load reduced (AC cycled off) sputtering for a second and generator shuts down. Not sure what inverter style means but definitely the generator normally cycles up or down when loaded or unloaded. Time will tell if reducing oil helped.

Yes...inverter style generators ramp up and down depending on the current load. When A/C turns off...generator drops in RPM. Is it staying on now or do you still have the issue? If so, you might change the plugs(s)...thus the sputtering.
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Old 06-24-2019, 01:48 PM   #19
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THOR #12484
Itís staying on now and It will have a lot of chances to disappoint in the next couple of weeks during a 2 week trip coming up. Iím going to change plug and oil this week. Would oil viscosity maybe make a difference regarding heat. Should I use something higher than straight 30w. Would 10-40 have better performance if heat is the issue.
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Old 06-24-2019, 02:04 PM   #20
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Originally Posted by mstng View Post
Itís staying on now and It will have a lot of chances to disappoint in the next couple of weeks during a 2 week trip coming up. Iím going to change plug and oil this week. Would oil viscosity maybe make a difference regarding heat. Should I use something higher than straight 30w. Would 10-40 have better performance if heat is the issue.

Somehow I missed your Post 14 and didn't realize you had it going. Stay with the oil recommended by Onan...period. Viscosity shouldn't cause the problems you were having nor would changing viscosity affect ability to cool. While oil circulation is a factor in the heat reduction process, airflow is the biggie there. Mine is water cooled. If yours is also, check coolant level. If not, open cabinet plates and make sure nothing has built a nest anywhere, interfering with airflow.
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