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Old 03-28-2010, 04:43 PM   #1
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Onan Generator Life Expectancy

Does anyone know how long these Onan Generators can be expected to last? Assuming you change oil on schedule, is there a number of hours after which time they are likely to fail or have problems?

Who has the most hours on their Onan diesel generator? I am looking at a used 2002 RV and the 7.5 KW (diesel) generator has nearly 6500 hours on it. That is way more than most of the generators I have seen on used units. I usually see readings in the hundreds of hours on used units.

I know everyone says don't worry about the number of miles on a diesel engine as they are like the energizer bunny (keep on going and going). But my experience with cars is that the power trains start seeing problems after 120,000 miles (yes, there are exceptions but there is also a reason why the trade in on high mileage cars is dramatically lower).

Anyway, if I get an RV with a generator that has 6500 hours, should I expect to replace it soon? Is it on borrowed time? Or am I worried about nothing? Of course, there is also no way of knowing if the generator maintenance was even done (although I guessing it was or it would have failed already).

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Old 03-28-2010, 04:56 PM   #2
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Question Running Hours ?

I have heard of 2,000 hours, but not of 6.500 hours. Seems very high.
Maybe phone an ONAN Dealer (CUMMINS) and talk to the Service Manager about those hours and the Dollars for an overhaul or replacement.
Get a discount on the Motorhome in that amount!

Good Luck

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Old 03-29-2010, 09:18 AM   #3
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I know of several folks with well over 2000 hours on the Onan diesel genny (I've got 1500 on my 2004). 6500, though, is a lot and I would start thinking about mechanical wear on the electrical parts and cooling system as well as the engine itself (which is a Kubota, by the way).

To me, that number of hours would be a real negative (risk of a very expensive repair) but not necessarily a show stopper if the price was right and everything else was primo..
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Old 03-29-2010, 09:37 AM   #4
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Cummins/Onan tech @ Rocky Mountain Cummins told me that with correct maintenance and service there is no reason why it should not give 10,000 hours service.
Michael (Home base Northern CO)
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Old 03-29-2010, 10:43 AM   #5
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Just curious, how many miles does the coach have on it? I guess I won't worry about my diesel genset with only 780 hours.
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Old 03-29-2010, 01:09 PM   #6
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I have a 1991 coach w/ that Onan 7.5 diesel and it has 2,600 hours. It has been maintained well and runs very strong. No sign of problems. 6k+ hours... that is a WHOPPING amount of time for that gen to be running for the year of the coach.
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Old 03-29-2010, 07:51 PM   #7
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I'd think that with 6500 hours it was used to power the AC while going down the highway.
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Old 03-29-2010, 09:00 PM   #8
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It's said (and I believe it) that an engine suffers more wear by starting it than many hours of USING it. This is why pre-lubers are around.

6500 hours comes out to 271 days. If you bought a generator (or any 'motor' for that matter) and just used it non-stop for 9 months (except to stop and change oil), would you expect it to be worn out?

Just a thought!
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Old 03-29-2010, 09:43 PM   #9
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I am a heavy gen user being in music and minisrty. My last Onan guiet diesel 10kw had over 6,000 when I sold it and it ran and operated like the day it was new. Entertainers start a gen when they leave on tour and seldom shut them down. I have run my gen for 3-4 days continually in the hot summer without 2nd thought. I would think 10-15K hrs would not be a killer. 20-30 not out of the question.
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Old 03-30-2010, 06:30 AM   #10
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Lack of use is frequently harder on equipment like a generator than heavy use. In addition to changing oil, a generator needs to be run under load, so allowing it to sit can cause damage. Running it under load helps keep moisture out of the generator coils.

6,500 hours sounds like a lot of use, but it probably isn't bad for a diesel. For comparison, if you averaged 40 miles per hour in the motorhome, you would drive 260,000 miles in 6,500 hours.
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Old 03-30-2010, 06:42 AM   #11
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To the post about using it going down the road, one of the first things my wife tells me when leaving home in the summer is, start the generator so I can turn on the air.

Even in the winter, we will use it sometimes to make coffee and a lot of times I forget to shut it back down. Gasoline engines like to run not sit.

I have a Sears garden tractor that is a 1974 model. Bought it new, use it a lot, never an engine problem, runs great. I think its going to outlast me.
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Old 03-30-2010, 01:04 PM   #12
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I'd rather than a generator that had been run 1,000+ hours/year than one that has been run just 10 or 20.

I've heard Onan guys say that when it comes to high hour generators, they are almost always overhauled/replaced just as a precaution rather than having actually failed. Most failures are from, you guessed it, low use generators.

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Old 03-31-2010, 05:53 AM   #13
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Thanks for the posts. I was thinking that was way high, too.

But having been in the Army, I remember we ran (mostly gas) generators in the field, pretty much run them 24/7, shutting down primarily for fueling and occasional oil changes and preventive maintenance. Of course, we had dedicated mechanics to tend to them to make sure they ran well. But I am quite sure these generators had thousands of hours on them. It did seem like one they got going, they never had problems.
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Old 03-31-2010, 06:16 AM   #14
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I don't think hours in excess of 5,000 is out of the question with proper maintenance and TLC. Not unusual to see refer units on refrigerated trailers with well over 6,000 hours and still going strong. Some of these diesel refers have service intervals of 3,000 hrs.

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