20 RESL overspeed

Kohler Home Standby & Commercial generator troubleshooting and repair questions
Birken Vogt
Generator Guru
Generator Guru
Posts: 661
Joined: Sun Nov 11, 2018 12:02 am

Keep us posted. I still think the problem is mechanical.
nrp3
Verified Dealer
Verified Dealer
Posts: 176
Joined: Sat Nov 10, 2018 9:56 am
Location: NH

So I tried another controller. It ran great for about 10 minutes and back to the same thing. Over speed, over frequency. I can push the stepper back to an acceptable frequency but almost immediately it’s pushing back against my finger to higher speed and shutdown. There is something about it sitting and then warming up to make this happen sooner. Like before it starts right off at 64hz. Something is still affecting input. Voltage stays at about 238v regardless of speed.
nrp3
Verified Dealer
Verified Dealer
Posts: 176
Joined: Sat Nov 10, 2018 9:56 am
Location: NH

Going back to what you said about mechanical issues. It will run, albeit rougher with no air filter. It will run with a filter with either cylinders’s plug wire disconnected.

Now that I think of it, it seems like the time I found a missing butterfly on a Generac 990, but the butterflies are still there in this case.
Birken Vogt
Generator Guru
Generator Guru
Posts: 661
Joined: Sun Nov 11, 2018 12:02 am

Very strange. I never liked that original RDC controller. I have hatched a plan in my mind to replace it with an RDC2 controller. The main generator, stepper, engine, etc. "should" all be the same. And the RDC2 does not use the MPU. Just uses AC frequency to control speed. Most of the wires are the same. But that is an expensive and risky proposition.

Another thing you said. I have never seen a Kohler engine that ran any different with the air filter off, on, dirty, or clean. So that is a little suspicious.
nrp3
Verified Dealer
Verified Dealer
Posts: 176
Joined: Sat Nov 10, 2018 9:56 am
Location: NH

So I’m going to try compression cold and warm on both cylinders. Possibly a leak down test as well. Pull off the throttle and look again. Take off some of the shroud tins and look further.
nrp3
Verified Dealer
Verified Dealer
Posts: 176
Joined: Sat Nov 10, 2018 9:56 am
Location: NH

Compression was similar on both sides warm and cold, around 155-160. Pulled of some shroud tins and poked around. Still doing the same thing. I took off the whole intake manifold and looked it over. The only thing I could see was a slight binding on the black stepper arm bushing, the kind that snaps onto the linkage. I took that off and got one of the white plastic ones with no clip and bolted the whole thing back together. Now it runs pretty much the same with or without the air filter and doesn't run away after ten minutes. That was the only part replaced this time. Why this became a problem two years later, I don't know or whether I had something of a vacuum leak at the cylinder heads. Ran it through a simulated outage, ran the 20 minute exercise, and more full speed manual run time and the problem is gone for now.
Post Reply