Does anyone know how to repair Genset generators? I have tested the windings, the diodes and capasitor all seem ok. threis not an AVR. when i excite the capasitor the voltage comes up but won't stay, but the spark from the excitation almost blows the cap lugs off.i can repair most generators but Gensets seem to be a problem.

Most of the time it is either the Capacitor or AVR that has blown. Check out our videos on how to test them.
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all the operator can ck on this if ckt breaker is closed on genset panel , this controls output power to all the outlets on genset , if that's not to be found as cause then a qualified serviceman will be needed to further diagnose problem

The voltage regulator for the generator is not work, replace it. Why, if there no dc voltage to excite the stator it won't any output. GB...stewbison

There are a few more components to check in the system. From the information provided this is not a Kohler generator as Kohler makes all their own AC alternators under 350KW, seems you may have just a Kohler engine (probably a CH25). Cannot find any info on the voltage regulator which leads me to believe it may be integrated into the main controller. Curious to know who the manufacturer is. If the capacitors are good, try checking the diodes. A volt/ohm meter with a diode check will do. Voltage reading on one side and nothing on the other. If you have no access to a diode check feature, try reading it through a battery NOT SHORTED TO BATTERY hook a meter to a battery and put the diode between one of the leads to the positive, one way will read voltage the other will read open, no voltage, or OL. Look for any fuses or breakers blown / tripped. 6 VAC on the output is about residual voltage meaning voltage the alternator makes without any help from a voltage regulator or field voltage. This usually means the alternator / rotor windings are still good. This alternator is brushless so you could seperately excite this unit via a 12V battery through your field. Look for your exciter field winding, it should have some kind of label on it saying F+ and F-, apply 12V here momentarily on + & - respectively with the unit running and you should see your output voltage spike. This tests the alternator. If this tests ok, then check to make sure your wiring / fuses from the alternator to the controller or voltage regulator (voltage sensing leads) are ok. If all these check ok, it is likely you have a bad voltage regulator.

Hi, a word of caution, use a 9volt battery instead of 12v to check the rotating field winding. The 12volts from a car battery or battery charger can burn out windings in a generator. I would say that your avr is pooched. There are 4 leads that go back to the windings in the generator from the AVR. Two of these are connected to the power output and two go to a separate winding in the generator. This is the exciter winding and this supplies power to the avr for the rotating field. The two to the power output are voltage reference only. If your generator has these exciter winding, you should check if you have voltage there with the 9 volts applied to the rotor. If you have voltage on the power output and not on the exciter, then the exciter is shot and your avr might not be. Try this first, if you could, could you take a picture of the windings at the back end of the generator, this will confirm for me what leads you have present.

If your generator has brushes you may need to "excite" the generator with a 6 volt battery

Make sure it is not the brush set.
There must be continuity from one slip ring to another.
If not, but rotor doesn't look burnt - check points where rotor wire is soldered to slip rings, or clear contact point on each side of wire and check continuity there, past slip rings and brushes. Big chance that wire came loose from slip ring.
Had such problem on my Champiion 3500
evern if burnt - rotor is easy to rewind at home, unlike stator.

Unless your model is Inverter type - there is AVR module.
But, unless your rotor has continuity - don't bother going further.

chek brushes...if they seemed ok then replace AVR card

Replace the sockets they have most likely gone bad, I have found this on a lot of generators I've worked on.

Glad to hear it was easy :-)
Here is a link to my trouble shoot solution so that this will get marked as solved.