Generac 25kW QT02516ANSN

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Dayl1ght
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Mon Aug 12, 2019 10:36 pm

Recently we had a hurricane and my generator ran for 15 hrs with no problems. At 5am the generator shut off as I was getting ready for work. (I'm a power lineman). I hurried outside and noticed the generators antifreeze was boiling out of the overflow tank, so I reached around to the control switch and turned it to the off position not looking at the error code(if there were any). After I got home from work and not looking any further that morning, I checked on the generator and noticed that the exhaust manifold had broke at the pipe where the four exhaust ports meet which then caused the inside to get hot and melt the top of the overflow tank. I replaced both with new parts. Now with the back story over, the generator starts fine but is running wide open (which i believe is the cause of the previous problems). I have ohm'ed the stepper motor and checked the throttle arm and everything seems fine. If i push the stepper motor back to close it opens to wide open throttle when trying to start. I don't believe a bad stepper motor would move correct? If i hold back the throttle arm and start the engine it runs perfect. I was thinking that it is the control board on the R-200A but if the control board is bad would it even start? I've done many test like draining the antifreeze a little and starting it by holding back on the throttle arm to not over rev and the engine shuts off as low coolant. Also tried to start motor with fuel shut off and get a light indicator of that. So can some parts of the circuit board be bad while other parts work? I'm truly at a loss.
Chris
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Mon Aug 12, 2019 10:50 pm

The controller can have specific functions die and others work, that's usually the case actually.

If the stepper is moving that's a good sign it's working. What's odd is that the controller isn't killing it for overspeed which is monitored by the mag pickup.

If the board is getting a strange mag pickup signal it could cause the issues.

I'd pull the pickup and make sure it's not covered in metal debris.
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Dayl1ght
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Thu Aug 22, 2019 10:51 pm

So I ordered a new mag pickup from Generac and installed it and I'm still having same problem. If I unscrew the mag sensor further away from the fly wheel it doesn't even start and gives overspeed error. If i keep it close to the fly wheel then the engine runs wide open. Again to me the control board seems to be working if it shuts down when i back the mag pickup out. Can the stepper motor work one way and not the other?
Chris
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Fri Aug 23, 2019 10:12 am

I could have probably gotten it for you cheaper :cool:

When a stepper motor dies it can do all kinds of strange things honestly.

The mag pickup should be set at 1.5 turns out from just seated on a flywheel tooth. Too close and you risk destroying it, too far away and you'll get RPM faults (possibly a flashing overspeed light depending on the age of the gen)

The stepper can be tested with some very fine meter probes and a good digital meter.
Generac tech for over 12 years. I'm here to help!
"The only source of knowledge is experience" -Albert Einstein
Looking for Generac parts? Gentek Power offers the full line of Generac replacement parts! Shop Gentek Power Generac Parts
A list of my favorite Generator & Electrical Tools! https://www.amazon.com/shop/gentek_power
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