Yet another Onan 5500 Issue

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lonesta71

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Jul 10, 2014
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New to this forum but not RV'n. I've been searching the Internet for about a month attempting to find a solution.

My rig: 2010 Inferno Monster Edition w/Onan 5500

The Onan has a whooping 12 hours on it. It did sit for a spell so I performed a PM on it. New filters, oil and a nice carb cleaning. Starts and runs WITHOUT a load and/or breakers off. It will die when the ATS activates. I've disconnected the Onan feed into the ATS and it runs with output. I fashioned an extension cord and wired it directly to the Onan. It will power TVs, chargers, soldering iron BUT not a coffee maker. I tested it with a cord to rule out the ATS. Same end result with the cord.

A not-so heavy load (<600 watts) will kill the Onan with error codes:

First Code is 3 flashes
Upon pressing the stop button once I get a 1 -2 flashes.

I hope someone can shoot me some ideas other than a visit to a dealer; the nearest dealer is over four hours away.

Thanks in advance!

Travis


 
Here is an Onan troubleshooting guide from Flight Systems. Hope it helps  http://www.flightsystems.com/pdf/onan-rv-troubleshooing-guide.pdf
and this http://www.cumminsonan.com/www/pdf/manuals/981-0530C.pdf  and this  http://www.cumminsonan.com/www/pdf/rv/f-1123.pdf
 
Check your Onan owner manual (get one online if needed) for the 3-12 fault code, but I believe it is over-voltage. That typically means either the regulator is bad or the governor is not maintaining the proper speed (RPMs). The generator shuts down to prevent frying your coach electrical system.

Your generator maintains output at the correct voltage and frequency by increasing engine power as the load (amps) increases and thus keeping the engine RPMs constant. If it cannot maintain 3600 RPMs under load, the voltage will go high or low, depending on which way it is off.
 
Dying once a load is put in it indicates possible fuel starvation issues. Double check that the fuel filter you replace is seated properly and not sucking air when motor goes to full throttle under load. Could be a fuel line has gotten bent/crimped or otherwise restricted, could even be gummed up carb> 
 
In the case of an ONAN it might be an electrical issue as well.. ONAN's moniotr ac-output and if there is none shut down.

The code for loss of 120 volts is translated as Cranking speed too low 

I forget what it is.. ... So I pulled up an ONAN operators manual.. Fault code 3 means: (The first 3 flashes) Means, Check the 2nd level code.

On the 2nd level this is a cut and paste from the operator's manual:

INVERTER OVERVOLTAGE FAULT?CODE NO. 12
(Controller not able to regulate to rated voltage)
Corrective Action: Check whether the vehicle engine and genset share the same starting battery. If
so, and this fault occurs when cranking the vehicle engine, low battery voltage may be causing this
shutdown. Increase battery capacity or install a separate battery and battery charging system for the
genset.

He did say the second level was 1-2 flashes.
 
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