How to troubleshoot a locked rotor on a generator?

Hi,

if possible please check your speed sensors within your generator to make sure each is still functioning properly. Otherwise, you might have to replace the sensors before the code goes away.

Thank you.

Locked Rotor is reported as an overcrank fault "OC".

You first need to verify the engine fails to crank, which is likely a starter motor or start circuit failure.

If the engine cranks three separate times and then the OC fault occurs, it simply means the engine did not run... more likely a fuel issue.

But either can be caused by numerous reasons.

You need to repair your locked rotor then it will work

Kohler Generator issue 20 RES - YouTube

? 0:24
www.youtube.com/watch?v=CT9u64dZna0
Apr 28, 2012 - Uploaded by Jeremy vanEyk
Brand new Kohler Generator Test cycle issue. ... Oh, and Mike, good call on the carb--that happens on some 20RES models. ...Indicates Locked Rotor (Lr). ... I'm on my second 20 RES-L,home depot swapped out the 1st one. ... Kohler 20KW RESA Whole House Standby Electrical Generator - Duration: ...

A generator must be able to put out the locked rotor amps listed on unit in order for it to start . Locked rotor is usually 4 to 5 times the normal run amps .

Check, capacitor rotor brushes and slip rings for cleanliness. Check for DC voltage on rotor brushes during craking. If still nothing try flashing the rotor, after that check rotor windings and stator.

I had this fault show this morning. Very alarming, as we have a typhoon coming theough tomorrow!

Turned out to be an easy fix. When I hit start the solenoid engaged but nothing moved. Then I saw the fault message and thought "Large $$$$!"

It was just a bad 12 Volt battery, and when it couldn't crank it threw the fault code. I replaced the battery, pulled the 3 fuses on the control panel (mine is the 20 Kw model), and the codes cleared, and she fired right up.

The advice here and on a couple other sites about powering down the panel to clear fault codes saved me a lot of time, money and aggravaion, not to mention a freezer full of food (knowing the Guam Power Authority, and knowing typhoons, the power WILL go down tomorrow.

You do not say what type/model generator you have, so I will just give you some basics.

There is nothing wrong with the magnets. Their power did not change at all, their pwer never changes, except to degrade slightly over time (hundreds of years.)


The generator rotor is hitting the stator. In other words, the alignment of the rotor inside the generator is off center, making the rotor bind on the inside of the stator, resulting in a lock-up.

With the generator attached to the motor, remove the generator end, and slowly try to turn the engine over by hand. REMOVE THE PLUG WIRE FROM THE PLUG FIRST, so that the engine cannot start. Watch inside the generator, and discover why the generator rotor is not aligned. Pehaps the bearings were installed incorrectly, or the housing is installed incorrectly. Most generator engines have a tapered power-takeoff shaft, where the gen. shaft connects to it. Is this Bolt tightened to specifications? Is there some debris floating around in the gen. (such as a screw, or a pebble, or a nut) that would impede its movement?

good luck

Poor grounding on the generator or connecting wires. Weak breaker on the generator. Locked rotor amps to high for generator circuit. Weak capacitor causing too high amps for generator.

Remove all wiring. Remove four stator bolts. Remove stator. remove rotor through bolt tap end of rotor us a shaft in the rotor tighten bolt in tapped hole to remove rotor.