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Old 12-29-2015, 07:50 PM   #1
Join Date: Sep 2013
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7500 Onan diesel

Generator has been running fine as of last trip
Come home today to fire it up to make sure it was ready for cold weather and it won't start and light flashes 3 times Service indicated
Any thoughts ?
04 40 Mds alpine

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Old 12-29-2015, 08:40 PM   #2
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how much fuel in your tank? if under half try adding fuel.

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Old 12-29-2015, 10:17 PM   #3
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Plenty of fuel in tank
Code is 14 on generator
It starts up and idles low for about 3 sec and dies

Was working fine last time I used it

I did replace my Inverter but don't think it has anything to do with the gen problem
Any help?
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Old 12-29-2015, 10:38 PM   #4
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According to the owner's manual, three blinks indicate a service code. One blink is high water temp, two blinks is low oil pressure, three indicates a fault.
When it's blinking, press the "stop" side of the dash switch once and then count the blinks. For example, a fault code of 14 would be blink, pause, blink-blink-blink-blink, long pause, then repeat.

Once you have your fault code, I bet a google search for Onan 7500 fault codes will give you an answer as to what is the issue.

Good luck.
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Old 12-30-2015, 03:30 AM   #5
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What inverter do you have? The reason I ask is, if you have a Xantrex with AGS (Automatic Generator Start) it controls the generator starting, if you manually start it with the switch on the console, or at the generator, the XAGS will shut it down in a couple of seconds. Go to the system control panel, select the XAGS, change to "manual on" (IIRC, there are 3 settings, Manual On, Manual Off and Automatic) the XAGS then starts the generator within a few seconds and it will run normally. If you do not have a Xantrex disregard the above comments, but look for the same feature with your system.

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Old 12-30-2015, 08:01 AM   #6
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It's an xantrax pro sine 2.0
I don't know if it has auto gen start but their is an onan programmable start pad in the coach too and I turned it off
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Old 12-30-2015, 08:12 AM   #7
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I believe that fault code 14 is over voltage. I had a similar problem except mine was 13 under voltage.
Check the multi pin connectors to the genny. I believe there are two main connectors. In my case one of the pins inside the connector was arcing inside its socket. Check those first.
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Old 12-30-2015, 08:16 AM   #8
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Crawl under the generator and unlatch the cover on the bottom, if belt pieces fall out, there's your issue, if not, it could be several things, coolant level, oil level, coolant temp sensor, water pump....let us know what you find.
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Old 12-30-2015, 08:18 AM   #9
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Agree--the fault codes is the place to start--did genset function after new invertrer install but wont run now? Notwithstanding the codes, if genset ran with new inverter config installed, some likely issues are: 1] low fuel; 2] temp or oil sensors; 3] internal "brain" box issues; 4] one or more batteries in house bank gone bad; or 5] Onan-related charger conflict if you try to run Onan and Cummins engines at same time [solution: turn off inverter charge function as soon as Cummins is started].......
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Old 12-30-2015, 08:57 AM   #10
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i never started generator after inverter install until now so it could be related but dont know where to start
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Old 12-30-2015, 09:02 AM   #11
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My suggestion would be to disconnect shore power & disable the inverter to make sure the inverter is not interfering with the generator. If it starts & runs ok then check it with the inverter enabled. If that works then try plugging the shore power back in. Just some thoughts ...
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Old 12-30-2015, 09:14 AM   #12
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Simple stuff first--shut off the breaker on the Onan itself to isolate it and see if it starts and runs. Then try to introduce the inverter with charge function off, then on....Starting to sound like an inverter conflict, or AutoGenStart.....
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Old 12-30-2015, 01:04 PM   #13
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You said plenty of fuel. If you drop to about 1/3 of a tank at any time, even though you did not run the generator, the fuel line to the generator may drain back to the tank. This has happened to me many many times. It's a pain to get that monster running again.
Personally, I would keep trying to start it. Just don't over heat the starter. Try for 30 seconds, let it rest 30 seconds and repeat. Can take several minutes to get a responce. It will eventually start and run for 30 to 60 seconds and die. Keep trying, you need to get all of the air out of the line.
This dose not mean it dosenot need service. But needing service will not stop it from running.
Just my opinion.
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Old 12-30-2015, 02:10 PM   #14
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I have an on going problem with my Onan where the same code comes up every time I try to start the gen. Cummins said I have a defect in the computer board, which will cost $1200. to replace. I found a solution to work around the code that I have used for 5 years now, the generator works fine after starting. You have to cut off the power supply to the generator for about 20 seconds to clear the code by cutting off the chassis battery switch in the battery compartment. I have to do this every time I use the generator but for $1200 it's worth it. It may work for you.

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diesel, onan

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