My Kohler 12RES (Natural gas residential stand-by generator) is consistently failing its weekly self-test. The indoor control panel flashes indicating a fault -- the panel on the gen set flashes "OC". If I then move the rocker switch on the gen set panel from "auto" through "off/reset" to "on", it starts up without a problem. If set the switch back to "auto" and then go back inside and manually start/schedule the weekly test, it works fine that time, but fails the next week.

Almost exactly a year ago, the same thing happened -- after the unit failed its self-test several weeks in a row, it also failed to spin-up during an outage; the tech who came out found that the GM34969 ADC Controller was oozing red goo and claimed that it was intermittently failing to send power to the starter solenoid. He replaced the controller (for about a thousand dollars) and said things were OK. Unfortunately, he forgot to reschedule the weekly self test and I didn't reset it until I noticed many months later that it wasn't happening. Consequently, the gen set panel reads only about 9 hours of operation.

The one thing in common between now and a year ago is that we're again experiencing incredibly hot/humid weather.

About a year or so before the controller replacement, the ATS was replaced for failing to switch one of the phases (another thousand dollars or so).

I've tried contacting Kohler and they say "it's out of warranty, call your local dealer". The problem is that the dealer doesn't seem to know much more than I do (I was the one that actually diagnosed the previous ATS problem) except they have the service manuals.

I'd rather not plunk down another thousand dollars on another guess.

Any ideas on how to trouble-shoot this?

Thanks,
Jeff

Same problem here, with an 8.5RES model. These controllers seem prone to fail. Everything works fine on the second try, as Jeff said, but the automatic transfer switch/remote start won't work unless it starts on the first try. Any help would be appreciated!

It turns out there are at least a couple of "maintenance bulletin" items-- one is that the capacitors on the indoor (ATS) controller board either go bad prematurely or were undersized. The symptom is that the system will forget all of its self-test programming (i.e. no weekly test) after even a brief (i.e. too short to cause a spin-up) power failure. This requires a[n expensive] board swap.

The other is that there is a known issue with the starter relay(s). This was a relatively inexpensive replacement. Since the relay swap, we've made it through one summer with successful weekly tests/spin-ups (though this past summer was a relatively dry one, I have high hopes that the problem has been solved).

Since I originally experienced the issue, the local Kohler dealer has upped their game -- they have a new service manager; they're now very clued-in and responsive (and were the ones to diagnose/repair the bad caps and relays).