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94-Newmar · 07-18-2010, 07:37 AM

Ok genset gurus, I have a question....

Onan DKD Series 7.5kw Diesel genset (circa 1992) in our Newmar. Starts right up, runs fine, no hunting or rpm variation... shows 115-116v after starting but voltage falls to 110v after it's been running for 15 minutes or so. It will stay at that voltage. It's not jumping all over the place, it's very steady at 110v for the duration. I just happen to notice this voltage issue when I plugged in a small AC/DC converter for a laptop and the output showed me 111v on it's display. So I grabbed my handy Fluke meter and checked outlets sourced from either side of the breaker panel, all show the same. I checked before/after the transfer switch, ensuring I didn't have a contact issue.

The frequency while warmed up or first started hovers between 60.0 and 60.3 whether under load or not. It runs the A/C's and everything else inside just fine - never sounds like its loaded down, just hums along perfectly as always.

The engine rpm must be fine since Im seeing the correct frequency of 60.0 to 60.3, whether the voltage output is at 110v or 116v. We use our genset a LOT. We drydock for sometimes 4-5 days and run it continuously, it's never missed a beat. Again... everything is working fine just wondered if that voltage is too low or if it's something I should be concerned with.

Is there an adjustable voltage regulator on these units?
Anything else to look for?

Sure seems heat related to me since if we dont use it for a day or so and then restart it it will show 115v again, falling to 110 after about 15 mins of running.

I don't have a service manual for it, just a parts manual.

Gary RVRoamer · 07-18-2010, 09:35 AM

Odd that the frequency stays up while the voltage drops. Is that an inverter style generator, by any chance? I doubt it in 1992 but ???

Onan sells a service manual for the DKD - see http://www.cumminsonanstore.com/

94-Newmar · 07-18-2010, 10:15 AM

Gary, No it's not an inverter type. I may be worrying about nothing at all, just caught my eye - it could have been like this since day 1. I'll see if anyone else chimes in. Meanwhile I'll order the Service Manual - seems like a good deal for $18.00 just to have for any future issues.

Gary RVRoamer · 07-20-2010, 06:29 PM

Yeah, for an older genny, it is wise to have the manual handy!

RV Wizard · 07-21-2010, 02:45 AM

I think the higher voltage is just due to the fact that the generator is choked for warm up period. It may have been doing this since day 1. "If it ain't broke, don't fix it"!

94-Newmar · 07-21-2010, 06:15 AM

Well, its a Diesel.. so no choking. I agree... no need to fix something that isn't broken. I'll keep an eye on it's behavior now that I have a baseline voltage to work with.