Onan Genset low/no power

[DaveInIowa]

Good day all!
Day 8 of my first cross country trip in my 1994 Tioga Arrow.
I have had a wonderful time.
Central Iowa to Tucson and back. Return stops; Amarillo, Thunderbird Lake OK, Table Rock Lake MO.)
My issue.
My Onan Microlite 4000 starts and runs fine with no load. But seems to provide only minimal power when plugged into the RV. Then it will shut down after I add a load; Air, microwave. The 12v lights flutter, the Air or microwave barely run. (Much like when I lost half my service to my home.)
From my research; I guess I do not have an ATS (automatic transfer switch) as I have to plug the power cord into a box in the RV to supply generator power to coach.
I hear clicking (And always have) in the convertor (under the fridge) when the genset connects or disconnects power.
Power supply from shore power is fine.
I did notice the convertor fan did not run when the generator was supplying power, but does under shore power.
There is obviously a switch/regulator in the convertor that directs power from the source. When this issue developed; the switch would buzz/click as if the power from the genset was being turned on/off. The lights would go bright (for a second) when on the battery bank, then dim when on generator.
NOTE; during this flicker of power, the generator just purred like a kitten. No engine fluctuations in rpm. Except the one time I turned on all AC power; Air, micro, all lights. Then the convertor switch 'popped' all power was lost (except 12v) and the genset shut down.
So, is there a switch that is part of the convertor set that is bad?
Or is it in the Onan?
Thanks for all your assistance!
Dave

[DaveInIowa]

CharlesinGA wrote:
Go to the link below, and just enter IA for Iowa if that is still where you are located, change the radius to 250 miles in the dropdown and in the application dropdown select RV and it will find the Onan service locations in Iowa. Looks like a company owned location in Des Moines.

http://power.cummins.com/sales-service-locator

Charles

Thank you Charles. I had already done that and was pleased to see a dealer less than 50 miles away!
Just completed my 3500 mile trip in the '94 Tioga and He performed magnificently. (The genny thing would have happened anyway.)
It may be a month before I can get it in; but I will post results when I know them.

[CharlesinGA]

Go to the link below, and just enter IA for Iowa if that is still where you are located, change the radius to 250 miles in the dropdown and in the application dropdown select RV and it will find the Onan service locations in Iowa. Looks like a company owned location in Des Moines.

http://power.cummins.com/sales-service-locator

Charles

[MEXICOWANDERER]

Badly worn brushes or an open excitation rectifier can cause feeble, flickering lights. This is why I still carry an analog (needle type) AC volt meter. It is impossible for a digital meter to display flickering voltages. Once that issue has been decided, where to go from there? A bad AC line cannot "flicker" without causing sparks and smoke. The excitation circuit (including voltage regulator) can cause flickering. Onan regulators have never seemed to me to have flickered: They either worked or they didn't and when they did they could provide high or low voltage.

A shorted exciter rectifier usually produces steady feeble voltage. Should be noted newer diagnostic type Onans can have dozens of reasons why they do not work right.

But a carbon brush worn to it's extreme limit will provide misleadingly steady power until the instant a load is applied. It can pass a tenth of an amp excitation no sweat but try two amps and it falls on its butt.

Slip rings should be professionally lathe trued and smoothed if the carbon brushes have cut a channel in one or both. If the worn depth of the channel exceeds so many thousandths of an inch the slip ring assembly should be replaced. An out-of-round slip ring will beat the brush and rigging to death.

Brushes that allow flickering can be very hard on the voltage regulator. If brushes are found to be the issue, be sure to run the generator a full load for perhaps 20 minutes to prove the regulator has not been driven squirrely.

Internal brush rigging connections that have gone bad for some reason can also cause this symptom. If you cannot chase the problem down to short brushes, it's time to call a qualified Onan Technician.

[j-d]

DaveInIowa wrote:
I just thought of something that happened in the past; a couple of times when leaving to go camping,I was on shore power at home. I started the generator and plugged in. No power. I shut down the generator, plugged in, refired generator and had power. I thought this was a 'quirk' or SOP? So from there on I always had the rig plugged in before starting.

Spec B makes it a very "early" 4KY so it's good you posted that. It might still have that "oil level switch" that people blame for problems not realizing it was deleted in the more recent Spec's. Just an example, I don't think that's your problem.

But 4KY has a Logic Board, so I wonder if it checks to see if there's a load connected before trying to pick up a load. If so, might have concluded there was no load to carry, before you plugged in, but wasn't smart enough to see that you added load later. Long shot, just maybe.

[ksg5000]

Measure the output and post results. Don't fret over 22 year old Onan - they are work horses. If you don't have tools or are not mechanically inclined take the rig in and have someone look at the generator.

[DaveInIowa]

The generator has performed very well up until last week when this issue arose. Engine wise, it pops off easily and purrs. I did a cold weather test and it started at zero degrees this winter. (Did I hurt it?)
Here is the info from the tag:
4KYFR26100B
Assuming it is original it is 22 years old with only 350 hours (and I put 100 on it). I exercise it regularily.
Is this repairable or a new genset the norm?
The rig is in fantastic overall condition for a '94 and I do not mind putting $$$ into it.
I intend to keep it for some time. In my research I see new convertors are fairly reasonable and may have that done anyway to get it out of the way.
I just thought of something that happened in the past; a couple of times when leaving to go camping,I was on shore power at home. I started the generator and plugged in. No power. I shut down the generator, plugged in, refired generator and had power. I thought this was a 'quirk' or SOP? So from there on I always had the rig plugged in before starting.
A new genset would not be out of the question as I use it frequently for cool down in the summer on route to campgrounds.
And I hate something not working 😉

[j-d]

That converter may not be the best, but I agree with the conclusion by others that it is acting like the Microwave and the A/C that you cited. In other words, I, too, think the 12VDC lighting is misbehaving because the 120VAC that the 4KY supplies to the Converter is misbehaving. If Converter IS MagneTek, all it has is a switch powered by 120VAC to take over the 12VDC load from the Battery. If the 120VAC is fluttering, and makes that switch flutter, then your lights will be flopping back and forth from Battery Power to/from Converter Power.
I still suspect a problem with the 4KY. Had it been running well? Recently?

[ksg5000]

Given the age of your rig you converter is probably an older Magnetek which produces a constant 13.6 volts when hooked up to 120 volt power source. If your converter works fine on shore power but doesn't on Generator then the issue is unlikely to be your converter. Lights dimming when your operating the generator simply confirms that your generator isn't producing enough power to operate the converter.

[DaveInIowa]

thanks a bunch guys. I'll look into whether the generator is putting out enough voltage or not. I do know where the 30 amp circuit breaker switch is and that has never tripped during this situation. I have ran both the AC and the microwave several times with no issues, not to say that that isn't a problem now.
My best guess is it is the converter based on the sounds I was hearing. I'll look into it all. New converter actually seems pretty reasonable from what I've looked at on the Internet.

[ronfisherman]

Moved from Class C.

[j-d]

Suggest you add the full model number. Last character is Spec Code. Then ask the moderator to move this to Tech Issues. Sample of our tag:

So this genset is commonly known as "4KY Spec K." The numbers in between indicate features, when and where made, etc. 4KY-K is the key information.
Do you have a Service Manual? Some of the guys here have links to download one. I might be able to help but web crawling is not my strong suit.
We have a 31-ft Class C with a 15000-BTU A/C and a residential microwave. The 4KY will NOT reliably run both. It may be because the circuit breaker on the genset is weak. Haven't gotten that far into troubleshooting. It's a 30A Breaker on the SIDE of the control panel, on the generator end. Have you found it?
These gensets won't grab the load right after starting. There's about 30-seconds while it must be checking to be sure its voltage, frequency, etc are OK. Then it applies power to the output wiring. In your case the outlet you plug the shore tie into.
Did this problem just develop?
See if you can get into some troubleshooting charts.

[ksg5000]

Grab and multi meter and check the voltage at one of the outlets inside the Rig when the generator is running. If it were me I would focus on the generator rather than the converter right now - if your generator isn't providing enough power it's going to create problems with the converter.

Here's an FAQ on Onan Generator issues - might help

https://www.flightsystems.com/pdf/onan-rv-troubleshooing-guide.pdf

[DrewE]

What model of converter do you have? I would guess that the converter is bad, and probably that you ought to simply replace it with a newer one rather than attempt to repair it as it sounds like a very outdated design.

As I understand it, this model of Onan generator needs 12VDC to generate 120V AC (the field is externally excited). It sounds as though your converter is an old design that switches between battery and converter power using a relay, and presumably has a separate, better regulated low-power output to charge the battery. It seemingly is not keeping up with the 12V loads imposed by the RV when the generator is also heavily loaded.

It's certainly possible that the problem may be elsewhere, too, perhaps a bad ground or bad battery connection or similar.

You are completely correct that you don't have an automatic transfer switch for the generator.