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

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probably that you ought to simply replace it with a newer one rather than attempt to repair it as it sounds like a very outdated design.As I understand it, this model of Onan generator needs 12VDC to generate 120V AC (the field is externally excited).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.

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

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.

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.

Onan Genset low/no power | Good Sam Community

13 Replies

j-d
Explorer II
Feb 15, 2016
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
Explorer
Feb 15, 2016
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
Explorer II
Feb 15, 2016
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.

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Onan Genset low/no power

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