Kohler 30RES LOC code..checked coolant

SOURCE: my 3.5 kw kohler marine

Check that when you run it, it is not in fact making correct voltage (within about 10% is good), also make sure the engine is coming up to full speed, 3600 or 1800. You could check this with a multimeter that measure hertz. On the main output leads when the genset is running make sure it is getting close to 60 hz. or if you are in an area that uses 50 hz. check for that respectively. There are a couple things that would affect this, one would be your SCR module. There is a test procedure for this which you could find here. http://www.scribd.com/doc/50171916/tp6196-1 . I don't work on marine units, mostly standby so these manuals are for residential. Check your fuses, could even go as far as checking the wiring in the back and wiring and condition of the brushes and sliprings. These actually build field voltage to make 240 or 120 volts whatever your unit is configured to make. The brushes need to sit flat on the slip rings and on a unit with 10 hrs. the sliprings I can't imagine would be very dirty but check that as well. If you have an ADC2100 controller use this manual to go into the controller to verify that it is set for the correct voltage that the machine is built to make. The only other fairly simple thing to check that I've had issues with is if Kohler mounted a fuse block on the side of the cabinet mounted to the genset with no vibration isolation. Check these fuses while attempting to run the unit and make sure you getting steady voltage out of them as sometimes they will vibrate causing pulsed voltage to come out of them and can give you an intermittent UU, UF, or OC fault (undervoltage, underfrequency, overcrank).