Community Forums

timjet · 12-20-2018, 02:43 PM

I used my 7.5 KW Onan generator last week for about 2 hrs and noticed the light in the generator start switch near the drivers seat did not illuminate. Once at the CG I shut the genny down. The next day it rained all day, unusual for FL, but did not start the generator again until today.

I put the coach in storage after we got home and today I went back to the coach to retrieve the genny start switch to find a replacement for the burned out light inside the switch. I removed the switch from the panel but decided to start the generator to see if the action of removing the switch would get the light to working again so I reconnected it. The light didn't work but the generator would only run for about 15 sec after it started and shut down by itself. I tried 3 times with the same result. I opened the generator bay and noticed the start switch on the generator was flashing a no oil pressure code. I checked the oil and it's mid way between the full and fill lines on the dip stick.
Suggestions??

timjet · 12-20-2018, 03:42 PM

Some more info.
I changed the oil, coolant, oil filter, fuel filter, thermostat, and air filter last April. The coach is full of fuel. Maintenance has been maintained on this coach. I've got about 100 hrs on the genny since April.

britcon · 12-20-2018, 10:32 PM

I think Generator has sensor that shuts down if low oil ?
Maybe a faulty sensor, or loose wire ?

timjet · 12-21-2018, 03:35 AM

I didn't want to say that to influence anyone's suggestion but I'm thinking it's a low oil pressure switch or corresion on the wiring. Can someone tell me where the pressure switch is or how to test it?

Tha_Rooster · 12-22-2018, 05:47 AM

Quote:

Originally Posted by timjet

Some more info.
I changed the oil, coolant, oil filter, fuel filter, thermostat, and air filter last April. The coach is full of fuel. Maintenance has been maintained on this coach. I've got about 100 hrs on the genny since April.

Maybe coolant low, the coolant was refilled thru the refill hose not reserve tank. Any codes?

veraken · 12-22-2018, 06:11 AM

Quote:

Originally Posted by timjet

I didn't want to say that to influence anyone's suggestion but I'm thinking it's a low oil pressure switch or corresion on the wiring. Can someone tell me where the pressure switch is or how to test it?

If you go to the "Files" section (above left) and search on Onan, you can download the Service Manual for your generator. See section 12 for info on the oil sensor.

Podivin · 12-22-2018, 06:17 AM

I've read here of another generator shutting down the same way, and putting in oil to the 'full' line corrected the problem. The assumption was that the sensor wasn't reading correctly. It'd be cheap and easy to try that.

Soppy · 12-22-2018, 07:06 AM

Fill the oil to the full mark and it should work. When the oil is cold it does not flow as fast as when it's warm . When the cold engine is started , the oil pump will pump the oil from the crankcase to the various parts of the engine and this will drop the level in the crankcase enough to cause the alarm.

timjet · 12-22-2018, 07:14 AM

I've got some great ideas, thanks guys.
I think the fact that the coach was out in the rain for almost 24 hrs and it ran just before that has something to do with it.
The coach is under cover in storage now and we're expecting warmer dry weather. Before I dig into this to deep I'm going to take the coach out in the sun for a few hours and try again. If that doesn't work I'll change the filter and refill to the top mark. Then if that doesn't work I'll try and get to the oil sender and check connections.

Bob Hyatt · 12-24-2018, 09:10 PM

Had a friend that had this problem. He had changed his oil and filter, but did NOT level the rig before doing so. Was low on oil. It would run until it got enough oil pumped/splashed out of the pan to trigger a low oil pressure reading and shut the genset off. Cure was to level the rig, then add the needed oil.

travelinJ · 12-24-2018, 09:15 PM

The Onan generator in teh CS did the same thing....low oil was the culprit.

avfordguy · 12-24-2018, 10:06 PM

Onan 7.5 and 8.0 QD are noted for bad coolant temp sensors, replace it and see ifproblem goes away, did you have any fault codes?

timjet · 12-25-2018, 05:13 AM

Oil quantity is between the fill and full mark on the dip stick. Been that way for the last 100 hrs.

Coach is perfectly level.
The generator starts and runs for 10-15 seconds then shuts down. I tried 3 times.
The start/stop switch on the generator is flashing a low oil pressure fault code.

I haven't taken the top cover of the generator off yet to view inside and see if I can find the low oil pressure switch. That's my next step.

Anybody know how difficult the pressure sensor is to get to? I do suspect it's an electrical continuity issue and not a low oil pressure issue, but I may be wrong.

THenne1713 · 12-25-2018, 10:51 PM

OP switch is generally mounted within inches of Oil Filter, grounds ignition with NO oil pressure, and is OPEN to ground with engine running w/ good pressure. You may have to remove filter, and/ or sheet metal to access switch? Circuit board/ START SWITCH disconnects this switch during start; if you hold START POSITION and it runs, and it dies when released, it kinda verifies Oil pressure issue. If you installed 30w oil vs multi-weight, the thick oil maybe having trouble flowing to pressurize before it warms up, but the switch is cheap/ easy to replace, and if wiring problem, most like to see when you go to disconnect old. If you truly have oil pressure issue, try new filter and multi-weight according to weather/ temps?