epa007
Hi,
  Generac 0062480,Serial 8710781,17 Kw, using LP. Generator starts then engine fully accelerated and OVERSPEED shown in display. Error code 1200 also. Anyone with experience on this error? Thanks
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78buckshot
My first suspicion would be a faulty throttle stepper motor, it controls the throttle opening. I did have one that even threw tech support for a loop, they said replace the stepper - no improvement, then they had me replace the ignition mags - no improvement, I told the from the start I thought it was the controller but they didn't agree until it was the last thing on the list to replace, it took care of the issue.
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Geoff Z
Move to Generac Air Cooled Generators
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epa007
I measure resistance from RED wire to each of the others four wires coming from stepper. Red-Black 12.1 Ohms, Red-Orange 12.0,Red-Yellow 12.0,Red-Brown 12.0.Is it the controller? Controller Assy is J8371A.Comments welcomed.
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Niwatori
                   https://www.youtube.com/watch?v=Aozmc                               Is this what your stepper motor is doing this during the surging?  My generator was. The stepper motor tested good like yours.. I replaced the stepper motor as a trouble shooting step and it corrected the surging.  
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Niwatori
Bad link, trying again.  http://
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Peddler
When the generator is put into manual the first thing that happens is the stepper motor moves the throttle to wide open and then back to about 1/2 open on the lower quadrant.  If it isn't doing this then make sure you have a good connection at the controller with the stepper control wire.  Also make sure the upper throttle isn't hanging open as its return is spring loaded only.  If as the unit starts the throttle moves to a more open position it indicates that it is not sensing the AC voltage on the 19wire from one or both coils and thus thinks the generator is running 1/2 speed.  I have seen the kill wire fall off one coil and make the unit go to an overspeed condition.  You should have about 7 VAC I think on the #18 wire from the coils if both are putting out correct voltage.
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