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Kohler 12RES Overspeed Fault

Posted by sniffdog (My Page) on
Fri, Oct 14, 11 at 12:00

Has anyone had any experience with this type of issue? Engine starts, runs for about 3-5 seconds, races a little - and then cuts off. I suspect the sudden increase in RPM is causing the engine to cutoff but am not sure what couold be causing it.

I have the service manual and am just starting to trouble shoot the problem. Just wanted to see if anyone else has run into this and can point me to a possible cause and fix.


Follow-Up Postings:

RE: Kohler 12RES Overspeed Fault

IMO something like this should only be looked at by a qualified service tech.

You could turn one screw and make it even worse. Not worth it IMO.

RE: Kohler 12RES Overspeed Fault

"sniffdog"-Does your set have electronic governing? If so, do you know where the speed pickup is derived from? I know larger sets generally have a flywheel pickup, but some smaller sets use the generator end output as a frequency reference.

Could be as simple as a loose connection or binding actuator. If you can manually access the throttle, hold the engine speed down a bit and see if it will continue to run.

"petey racer" - I used to agree with your thinking, until I realized that labor rates for service these days makes buying a service manual and doing your own repairs a very profitable idea. I recently spent a few hours and about $50 in materials repairing a set that two (qualified? they had fancy trucks with the name of a generator company on the door) service companies had left unserviceable after $1000+ of labor.

RE: Kohler 12RES Overspeed Fault


thanks for the advise. I ran through the procedure in the service manual and fixed the problem. I first checked the contoller to make sure all of the configuration parameters were set properly - and they were. I then checked to make sure that the electronic governor was working properly by manually moving the throttle linkage to open and close the carb butterfly valve and then starting the genset to observe the step motor move the linkage - and that fixed the problem. I saved myself 300 dollars - which is what it cost me the last time I had a tech out. And all he did was follow the same manual that I had.

I will do any routine maintenance or service that requires simple testing and part replacement (like repacing fuses, safety sensors, SCR module, etc). If it is something serious then I will call a service company in for help.

RE: Kohler 12RES Overspeed Fault

Since no fault was positively identified, is this fault likely to reoccur shortly?

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