Can someone please tell me if an "oil temp sensor" is the same thing as a "low oil sensor" in an Onan gas generator? I have been doing a lot of reading and have noticed that most of the problems with surging and shutting down of generators seem to be heat related, and may possibly involve that sensor. My generator, a 4000 watt KW, recently began having the same issues, which could also be caused by a bad fuel pump or fuel filter, but which I have yet to rule out. The dilemma I have is that my generator runs for some twenty minutes (in So. Ca. heat exceeding well over 100 degrees, in the shade, parked), before shutting down, which in my mind, would rule out those two as the culprits, otherwise, I believe the generator would not run at all, I think. The problem is that I don't know if my particular generator even has one of the sensors I mentioned. Can someone please help me? Thx.
Onan oil temp sensor
- Thread starter cgmartin
- Start date
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Gary RV_Wizard
Site Team
I've not heard of an "oil temp sensor" in any Onan, but that doesn't mean there is no such thing. Where did you read about it? Some Onan Microlite 4000's do have a low oil switch, though, so please identify the specific Onan model you have. There should be a plate on the genset showing the model & serial, e.g. 4KYxxxxx.
Later model Onan4000's give a fault code when they shut down, i.e.blinking light on the switch. That gives a clue as to why it shut down. See your owner manual for codes.
Later model Onan4000's give a fault code when they shut down, i.e.blinking light on the switch. That gives a clue as to why it shut down. See your owner manual for codes.
I downloaded the parts manual from the Onan website for my 4K Onan generator. It shows a "switch, oil level", part number 308-1059, to the right of the oil pan. The terms of oil temperature sensor and low oil sensor are used on this site, as well as others, who have indicated that mot of the time, when a generator shuts down, it is likely because of this sensor. I am getting a code 36, which could mean a number of things. My oil is between the low and the high mark. It runs great for twenty minutes or so, then sputters and dies. It will re-start when it cools off, but then will die again after 20 minutes. This is with motorhome parked, and no load.
Gary RV_Wizard
Site Team
There are oil level sensors and there are coolant temperature sensors on the water cooled models, but I've never encountered an oil temperature sensor on an Onan.
As has been mentioned, the 4KY Onans are splash-lubricated and so require a certain oil level. I would start by making sure the oil was at the Full mark, just to easily eliminate one possible cause.
The code 36 is unfortunately a catch-all. In addition to low oil, it could be a cruddy spark plug, dirty fuel filter, cracked fuel line, weak fuel pump, dirty air filter, etc. It basically just means the engine stopped running.
As has been mentioned, the 4KY Onans are splash-lubricated and so require a certain oil level. I would start by making sure the oil was at the Full mark, just to easily eliminate one possible cause.
The code 36 is unfortunately a catch-all. In addition to low oil, it could be a cruddy spark plug, dirty fuel filter, cracked fuel line, weak fuel pump, dirty air filter, etc. It basically just means the engine stopped running.
catblaster
Well-known member
Someone else on this site had the same problem, when they changed from synthetic oil to conventional oil the problem went away. The sensor you have is a pressure switch, they often go bad and the symptoms are like yours. It starts, runs for about 20 minutes and shuts off. restarts and goes thru the same thing. I suspect that since these engines have a very low oil pressure even when new so as the engine gets older or the oil gets hotter and thins then the switch trips. I just had to replace one on a welding machine for the same problem.
catblaster, I am beginning to believe you may be right. Yesterday, I went ahead and added a little bit more oil, but not to the full mark. I then ran the generator and waited for it to shut down. It never did and I got tired of waiting and shut it down. It was around 8:00 pm and a lot cooler then, so I don't know if the ambient temperature had anything to do with it. Nonetheless, I will be changing out all the rubber fuel hoses, all the way to the gas tank, changing out the fuel filter, gas pump, spark plug, air cleaner, low oil sensor, as well as changing to 15-40 conventional oil (temps her are 100 in the shade). The carburetor is less than two years old, so I will be leaving that alone, for now,but I will be running some Sea Foam thru it. Thx to everyone for your input.
catblaster
Well-known member
copied this from Onan manual....
NOTE: Multi-grade oils (such as SAE 15W-40) are recommended for year-round use in Cummins Onan
liquid-cooled engines, or as a good all-season oil for air-cooled engines.
NOTE: SAE-30 is the preferred summer grade for optimum oil consumption control in Cummins Onan
air-cooled engines.
it also had a chart that showed 30w when temp is above 32 degrees. https://power.cummins.com/sites/default/files/literature/rv/F-1123-EN.pdf
pg 29
NOTE: Multi-grade oils (such as SAE 15W-40) are recommended for year-round use in Cummins Onan
liquid-cooled engines, or as a good all-season oil for air-cooled engines.
NOTE: SAE-30 is the preferred summer grade for optimum oil consumption control in Cummins Onan
air-cooled engines.
it also had a chart that showed 30w when temp is above 32 degrees. https://power.cummins.com/sites/default/files/literature/rv/F-1123-EN.pdf
pg 29
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