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Rich Biebel · 07-12-2019, 07:45 PM

I sent you a reply to your email

The generator needs to be load tested independent from the Coach.

I use a 10kw resistive load bank to test all machines.

I would disconnect the wires from your Coach to the Onan and connect my load bank and test the generator right up to its full rated output....

That's about 62 amps from memory....

This will verify if the issue is the generator or something in your coach and trust me it is possible your inverter or something else like an AC unit is the problem and not the generator...

I have worked on and repaired many 7.5's and have not found the binding governor issue that Onan mentions in a service bulletin...

The control is not a separate part. It is part of the generators inverter section and is only replaceable as a complete new unit. Very costly to replace......so the load test is a must BEFORE the unit is pulled out of the coach......

I've seen this problem before and it was NOT the generator.....

The control unit section is all PC boards and the inverter section is the same....PC boards and high voltage components....all one sealed unit......

I've had 7.5's do some really unusual things......Start cranking the engine on its own with no switch signal to start. Had another one that would full field the generator end while trying to crank the engine. The starter would burn up trying to crank the engine.

I just did one where the unit started cranking and smoked the starter.....Pulled it out and replaced the control/inverter section along with the starter and other parts.......

Don't be confused when I say inverter. Your generator IS an inverter type machine and I'm not talking about the inverter in your coach.......2 totally separate things....

07-12-2019, 07:45 PM	#4
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,275 Likes: 25 Liked 510 Times in 200 Posts	Re: Onan 7500 33 code error I sent you a reply to your email The generator needs to be load tested independent from the Coach. I use a 10kw resistive load bank to test all machines. I would disconnect the wires from your Coach to the Onan and connect my load bank and test the generator right up to its full rated output.... That's about 62 amps from memory.... This will verify if the issue is the generator or something in your coach and trust me it is possible your inverter or something else like an AC unit is the problem and not the generator... I have worked on and repaired many 7.5's and have not found the binding governor issue that Onan mentions in a service bulletin... The control is not a separate part. It is part of the generators inverter section and is only replaceable as a complete new unit. Very costly to replace......so the load test is a must BEFORE the unit is pulled out of the coach...... I've seen this problem before and it was NOT the generator..... The control unit section is all PC boards and the inverter section is the same....PC boards and high voltage components....all one sealed unit...... I've had 7.5's do some really unusual things......Start cranking the engine on its own with no switch signal to start. Had another one that would full field the generator end while trying to crank the engine. The starter would burn up trying to crank the engine. I just did one where the unit started cranking and smoked the starter.....Pulled it out and replaced the control/inverter section along with the starter and other parts....... Don't be confused when I say inverter. Your generator IS an inverter type machine and I'm not talking about the inverter in your coach.......2 totally separate things.... __________________ Rich Biebel S/C 1479 Last edited by Rich Biebel; 07-12-2019 at 07:54 PM.