I have a 7500 watt Onan generator. It starts and runs fine for 20 minutes and then shuts off regardless of "no load" or with lights and a/c on. I put on a new fuel filter, and both coolant and oil are at proper levels. Checked radiator temp when running, and it is at about 165 to 175 degrees. After it shuts down, the red light on the start swith flashes 3 times. The label next to the start switch states "needs servicing". Does anyone know what might be the problem, or what needs to be serviced?

If you push the button second time when it is flashing 3 times it will flash a 2 digit code with a short pause between the two digits. Mine was throwing code 36. Although my generator is a gas 5500 may be similar. Heat and the fuel pump. I was in last week for warranty service and they ordered new fuel pump. I get it installed tomorrow. There have been a few posts on here about it recently. Mainly the gas 5500 model. Onan repair said they have had to move the fuel pump on some generators due to the heat.

hotjag1, Well Sir, this may be caused by the infamous "sending unit" located in the lower thermostat housing. As has been stated, a secondary push on the stop switch should reveal a secondary code. If, you push it and, it flashes three times, then a short pause, then three more flashes then, a long pause and then, it repeats the sequence all over again, that's what's known as code "33". And to many of us, it means an "Over heat condition". The causes are:1. Clogged cooling air intake (leaves, debris, etc)2. Low coolant3. blocked or clogged exit for the cooling airand more. But, quite often, it's not any of those causes. Quite often, it's corroded probe, on the end of that sensor. You see, that little sensor, is about the size and shape of a spark plug. And the sensor probe, which is very close to the size of 14MM spark plug threads, resides in a very tight, bore in that housing. But, what commonly happens is, even though your coolant can be clean and green, that probe has very little coolant flow around it due to the proximity closeness to the bore, and it starts to get corroded and, it will do it to the point that, the corrosion will seal the cavity between the probe and the housing. When this happens, the probe starts sending incorrect signals to the generator ECM. One of the incorrect signals is "An over heated condition" and, the engine is then shut down to protect itself even though the coolant is not hot, and, you have none of the other causes either. So, what's the answer here? Well, if you're capable and willing, the gen may have to be slid out, if you're one of those fortunate to have slide out Gen, or, it will have to be removed from the bottom and then get at that sensor which, can in many cases, be one serious pain in the a$$. Good luck.Scott

Thank-you for the replies to my question. I have only had this coach for about 3 weeks and have quite a few things to learn about it. I will check for a code or flashing sequence. I do have a slideout generator, so maybe I can get it figured out. The dealer I bought it from is putting in a new ice-maker next week, so I might let him figure it out. Thanks again!

Our Phaeton was doing the same thing. I found that Tiffin had put a second very small filter on top of the frame rail between the gen and the tire. I removed that and it's been running fine ever since. You might want to take a look and see if you have one too.

The filter that I replaced is the one above the frame rail near the tire. So is there another one inside the enclosed generator compartment?

Generator quits after 20 minutes | Good Sam Community

12 Replies

Heisenberg
Explorer
Aug 31, 2013
I am having the same issues with an Onan 5500.
Super_Guy_78
Explorer
Aug 31, 2013
I had same problem with my diesel Generator, it was the relay for the fuel pump
hotjag1
Explorer II
Aug 22, 2013
Just got my coach back from the shop. The problem was exactly what a previous post said it was. The generator showed a fault code 24. According to the tech, that meant it was giving a false reading that it was overheating. They replaced the thermostat and new sensor and it now runs continuously with no problems.
baldcamper
Explorer
Jul 29, 2013
Had the same problem with my 7.5 in a 04 HR Scepter. Turned out that the heat sensor in the side of the thermostat housing was cracked. Replaced sensor, no further problem.
Big_Katuna
Explorer II
Jul 29, 2013
The few times I have witnessed the dirty fuel filter symptom, they were the same; the genset would run indefinetly at idle and low RPM. It was when the 2nd AC would come on and the RPM's jump up to meet the load, it would starve and shut off as it couldn't meet the load.

Please let us know what you find.
hotjag1
Explorer II
Jul 29, 2013
JackMS...Thanks for the info on fuel and oil filters. I'll change that filter too and see if that helps. If not, the sensor problem described in an earlier post sounds like a common issue.
JackMS
Explorer
Jul 25, 2013
Yes, there is a door on the bottom. The fuel and oil filter are in there.
hotjag1
Explorer II
Jul 25, 2013
The filter that I replaced is the one above the frame rail near the tire. So is there another one inside the enclosed generator compartment?
always-ready
Explorer
Jul 24, 2013
Our Phaeton was doing the same thing. I found that Tiffin had put a second very small filter on top of the frame rail between the gen and the tire. I removed that and it's been running fine ever since. You might want to take a look and see if you have one too.
hotjag1
Explorer II
Jul 24, 2013
Thank-you for the replies to my question. I have only had this coach for about 3 weeks and have quite a few things to learn about it. I will check for a code or flashing sequence. I do have a slideout generator, so maybe I can get it figured out. The dealer I bought it from is putting in a new ice-maker next week, so I might let him figure it out. Thanks again!

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Generator quits after 20 minutes

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