The 7500 Quiet Diesel generator uses an Inverter/Control Board that monitors almost all your generator electronics. Onan provides you with fault codes to help you troubleshoot your system, but some fault codes are easier to understand than others when it comes to fixing the problem or in this case "clearing the code!"
Fault Code#46 fault code is one such code where there is little explanation given on what this code is and how to fix it. Some people say the only way to clear the code is to buy a new inverter (and have). I most certainly considered this a last resort especially since my generator was running fine.
These customers with a 46 Fault Code also complained about their generator started and then stopped or would not start at all. However, in my case I got lucky. My inverter worked fine, but I just could not clear the fault code #46.
The following is a list of the Cummins Onan HGJA fault codes. (Check with Cummins for HDKAJ 7500 Quiet Diesel Generators – to be sure this list applies.)
Code 2: Low Oil Pressure
Code 3: Service Check
Code 4: Over Crank
Code 12: Over Voltage
Code 13: Under Voltage
Code 14: Over Frequency
Code 15: Under Frequency
Code 19: Governor Actuator Overload
Code 23: Low Oil Pressure Cutoff Switch
Code 27: Voltage Sense Error
Code: 29 High Battery Voltage
Code 31: Overspeed
Code 32: Low Cranking Speed
Code 35: Control Card Failiure
Code 36: Engine Stopped
Code 37: Invalid Generator Set Configuration
Code 38: Over Current (Field Overload)
Code 41: Generator Rotor
Code 42: Processor
Code 45: Speed Sense
Code 46: System senses low voltage (battery) during start or bad Onan inverter.
Code 47: Ignition
Code 48: Generator Field Sense
Code 51: Processor
Code 52: Fuel Injector
Code 54: MAT Sender
Code 56 MAP Sender
Code 57: Over Prime
Code 58: Exhaust Gas Temperature Shutdown
Code 81: Exhaust Gas Temperature Sensor Open
Code 82: Exhaust Gas Temperature Shorted
Note: There is no code 33 since the system uses three blinks to signal a second-level fault code.
FAULT CODE #46 COMMENTS
* I got a Fault Code 46 and could not clear it. I first noticed this code after I returned to my RV in storage (2020) where I tried to start the ISC-350 engine and then the generator, using the "Boost Switch," but with no luck.
Then I used my tow car to jump the house batteries and I started the generator. Then I tried starting the engine… only to witness that when I turned the engine key it killed my running generator.
==> LATER I FOUND OUT THIS IS NOT ADVISED. …And it may explain why my Onan generator tripped a Fault Code #46, but this is just speculation on my part.
==> What I will not do in the future, if I have dead house and engine batteries, is attempt to start my engine, with a jump from a car or a tow truck, while the generator is running!!!
SO HOW DID I CLEAR MY FAULT CODE #46
(One of these 3 methods did it, but I don’t know which one?)
Possibility #1) I bought a battery repair charger that “pulsed” my house batteries back into shape! I have 4-6V-GC2-Golf Cart batteries and I used the 12V option to pulse 2-6V batteries (in series) at time, for 2 days, while I camped in my RV with the other 2-6V batteries connected to my inverter/charger. Then I repeated the 2-day pulse-repair on the other set of house batteries.
Amazon $32 Pulse Repair Charger:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
Note: I think this was the most likely reason my Fault Code #46 went away.
Most likely my sulfated batteries looked like a "short" when any heavy load was put on them; and no my house batteries would not last the night on inverter power. So I know my house batteries were very weak, but they all tested "good" with a voltmeter and a hydrometer and they passed a load test at Interstate Batteries. Just the same the "pulse-repair" charger de-sulfated the sh*t out of those batteries and my #46 Onan Fault Code went away!!!
However, I’m going to describe two more things I did to my generator, because I cannot say for sure which one of these steps was truly responsible for clearing the fault code?
Possibility #2) I was changing my Onan generator coolant and drained the old coolant with a cold engine. I put new coolant in, but it only filled about 2.5 quarts out of the 4.2 quart system. Then I started the engine (with the thermostat closed) and because there was air in the system… then generator ran for 5 minutes, and then shut down. Then I restarted it and it ran for 1 minute and shut down.
I had to do this 2 more times before the thermostat would open and allow the coolant to circulate. Then the generator ran fine after I zip-tied the filler neck up as high as I could stretch it.
From this experience, I would advise you to change your Onan generator coolant with a hot engine. ...But I have to wonder if the system cleared the #46 Fault Code when it shut the engine down due to a temperature sensor turning the generator off?
Note: The Onan 7500QD inverter/control board cost ~$2000 and it will cost another $800 to install it. So this is a big win for me and I hope if you experience a 46 fault code that you too find success.
Here's a good video on changing your Onan coolant: Change the Coolant in Your Onan Diesel RV Generator || RV Generator Maintenance
** Just makes sure you change the coolant with the generator fully warmed up so the thermostat is open.
Possibility #3) The other possible reason Fault Code #46 disappeared is because of this action: When I was flushing out the generator coolant, I decided to shut off the shore power circuit breakers even though I know the generator power had priority over the shore power as controlled by the Transfer Switch (ATS-5070)… but I left the power cord connected.
I ran the generator for about 15 minutes… and then I realized the shore power breakers only turned off the “HOT” wire leads (L1 & L2), but did not switch off the neutral wire.
So.. with the generator running, and the shore power breaker switches “off,” I pulled the 50A power cord out of the shore power socket… and I was surprised the generator died. Then I just restarted it and all was normal.
I don’t know why this happened, but I can tell you I no longer have an Onan inverter fault code #46 to worry about!
End.
JUST FOR GRINS: OTHER REASONS YOUR ONAN GENERATOR WILL STOP RUNNING AFTER IT STARTS
A: Diesel Generators notoriously need their diesel fuel filter changed. One indication of a clogged fuel filter is this: The generator will stumble and struggling to run after you start it. And when it’s cold it will crank for a longer than time than usual.
B: Your fuel tank is near the 1/4 tank level and your generator ran out of fuel.
C. You need to replace your temperature sensor, because it probably has some corrosion on it.
D. Your generator thermostat is stuck closed and the generator shut down due to over heating.
END.
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