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Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 14992
Experience:  Certified on Onan and Generac generators
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I have a Onan 7000 in my 2015 Tiffin motor home. The

Customer Question

I have a Onan 7000 in my 2015 Tiffin motor home. The generator has about 100 hrs on it but has had a number of failures in the 5 months we have had it. Its been worked on but still fails. However, it appears that it will run if I squeeze a little more oil in the crankcase by parking the MH on a slight downhill slope so the fill hole is at the back of the generator. Is it possible the sensor for low oil needs replacing?
Submitted: 1 year ago.
Category: Small Engine
Expert:  Hank F. replied 1 year ago.

What is the model number?

Customer: replied 1 year ago.
RV QG 7000Model #
7HGJAB- 900K
Expert:  Hank F. replied 1 year ago.

What fault code are you getting on it?

Go to the genset and use the switch on the set itself.
Press 'Stop' 3 times within 5 seconds. The light in the switch will start flashing.
If the light flashes 3 times, pauses for 3 seconds, and flashes 3 more times, press and immediately release 'Stop' one more time.

This will put the controller into Fault Read Mode.

The light will flash (X) number of times, pause for 1 second, and flash for (X) number of times again. Count the flashes before and after the pause.

This will be the Fault Code.

Example: 2 rapid flashes, 1 second pause, 5 rapid flashes is a Fault Code 25.

There may be more than one Fault Code stored, so watch the light very carefully. If there is more than one code, it will display them all in order, and then start over again.

Be very careful not to misread a first level fault code (single digit code) as a second level fault code (double digit code).

The way to tell the difference is by the length of the pauses.

There is a 1 second pause between digits of a second level code, and a 3 second pause between codes.

For example, if it is flashing 2 times, 1 second pause, flashing 2 times, 3 second pause and repeating, then this is a second level fault code of 22.

If it is flashing 2 times, 3 second pause, flashing 2 times, 3 second pause and repeating, then this is a first level fault code of 2.

What Fault Code are you getting?


Customer: replied 1 year ago.
The fault code is 36.I know what the manual says about that fault code & the problem is none of those things. It was just gone over thoroughly by the best shop in the area & it ran fine when it left the shop. It is intermittent as it has always been when we bought it new in May of this year.Please focus on my original question - could it be a faulty low oil shut-off sensor? It ran fine for several hours after I got it back from the shop & then failed when parked on a slight downhill slope. At that time the oil appeared to be full on the dipstick & was near the top in the oil fill hole. But, as I said, I was able to squeeze another pint or so of oil in it by feeding it very slowly on the slope since the oil fill hole was on the high side. Then it started right up & ran for 2 hrs or so until I shut it down. I just cranked it up now a week or so later & it is still running fine, but from past experience, it will fail again & I strongly suspect I will again be able too start it by "squeezing" a little more oil in the reservoir as I have done now a couple of times in the past. This does not seem normal to me, although a couple of other owners of this model have reported the same problem & the same solution (squeezing a little more oil in). Is this a design problem or could it just be a faulty oil level sensor?
Expert:  Hank F. replied 1 year ago.

No, it will not be a faulty oil pressure switch. They are either good or bad, there is no in between.

Customer: replied 1 year ago.
is the answer that this model is just very critical about oil level? Over-filling it seems to be the remedy so far & others on RV forums with this model have reported the same "fix". Its hard to believe that would be true, but it seems to be. What do you think? Any other ideas?
Expert:  Hank F. replied 1 year ago.

No, it is very doubtful that oil level is the problem. This unit has a pessurized system, and as long as there is oil in the pan, the pump is picking it up. The pickup doesn't know if the unit is a quart low, right up to full, or over full. But overfilling an engine can lead to severe engine damage.

Customer: replied 1 year ago.
you are basically telling me that the only thing I have found that seems to work could lead to severe engine damage? That is not what I want to hear since no one seems to be able to solve the problem any other way. What is your basis for that statement?It is also the only solution I have been able to find from other owners who have reached the same conclusion after eliminating all the obvious possibilities & having it thoroughly gone over by a qualified technician. I suspect this is a design problem with this model but I am also told that neither Onan nor Tiffin will acknowledge that & replace them. I may have to put more pressure on Tiffin since the MH & the generator are under warranty.
Expert:  Hank F. replied 1 year ago.

Your problem is not a low oil pressure switch.

Customer: replied 1 year ago.
Well if your're sure its not the low oil pressure switch, what do you think it is? How do you explain the experience I & others have had temporarily "fixing" the problem by topping off the oil? Isn't it possible it is a design problem with this model?
Expert:  Hank F. replied 1 year ago.

Without being able to see and hear it, and do testing on it, I could not say for sure what the problem is. It could be many things.

But it is not an oil issue. If it were, you would be getting a code 1 - not 36. As I stated before, the oil pump pickup sits down in the oil pan. As long as the oil is over the pickup, it does not know how much oil there is. And over filling an engine can easily lead to engine damage - all the way to a blown engine.

Yours, and others, "temporary fixes" are just coincidence.

I doubt it is a design flaw, or all units of that model would be having issues.

Customer: replied 1 year ago.
Seems to me that some tech would have found the answer if it is not a design flaw. There are too many owners out there who have had the same intermittent failures & tell me you have to keep the oil level on that model up to the threads of the fill hole to prevent the problem &, so far, that seems to be the only solution that has worked for me in spite of it being thoroughly gone over by an experienced tech, including removal from the MH & testing on the bench as well as in the MH & parts changed & still the same intermittent failures which seem to be overcome by topping off the oil. Others report doing the same with the same results & none have found any other remedy with the exact same symptoms. Your statement that it would be a code 1 if an oil problem is contrary to the manual which says that would be a code 2, but even so, it may be that the code reading is faulty. I assume you do not work for Cummins? Am I going to have to take it to them to get this resolved? It makes no sense to have such an unreliable generator on a new 100k+ MH.
Expert:  Hank F. replied 1 year ago.

Yes, a low oil pressure shut down will be a code 2, not a code 1. That was a typo on my part - sorry.

But a low oil pressure shutdown will not generate a code 36. If the low oil switch is not being activated, oil level should not have anything to do with it (unless, of course, the oil is so low it can not get to the oil pick up).

No, I do not work for Cummins. I work at an independant shop, But I have been certified for 15 years now.

I do know that it is very easy for a tech or 3 to not be able to find a particular issue, especially when it is some oddball issue that is not directly covered in the books.

Sometimes even the best techs get stumped, and an issue is found purely by accident.

Once in a while, a unit just needs to be seen by more than 1 tech.

Case in point - Last summer I had a unit that would run just fine as long as the coach was sitting still. But as soon as the coach hit the road, the genset quit. Obviously, sitting there watching and listening to the genset while the coach is going down the road is not an option, and testing is extremely difficult - if not impossible.

It took us 2 days,but we finally found the problem. There was a plastic bag down inside the fuel tank. As log as the coach was sitting, it was not a problem. But when the coach started moving, the plastic got sloshed around, and ended up getting sucked up to the fuel pickup, shutting off the flow of fuel to the genset.

If this were a desing flaw, there would be a service bulletin out on it, and there is not one.

Customer: replied 1 year ago.
Hank,I do not want to give you a poor rating, but frankly, your responses have not been helpful. You have discounted the only remedy that has worked for me & others with the same symptoms & have even said it could damage the engine or even result in a blown engine. And yet I know other owners who have been over-filling the crankcase with oil for years & hundreds of hours without such failures. In fact, one Onan dealer service department manager said "this model needs to be absolutely full & you can't over-fill it". You have offered no better solution.I know these intermittent generator problems are hard to diagnose, particularly when you don't have it in front of you. But generators are supposed to be built for reliability & in my prior experience, they are. For some reason these Onan generators used in MH's seem to be an exception, particularly this model. I really need to get to the bottom of the problem if it recurs. I will keep my fingers crossed that keeping the oil topped off will result in no more failures, but I agree it is probably more than just that.Maybe you should have just told me up front that something like this can't be diagnosed at a distance, before Just Answer charged my credit card.