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Kohler - unsteady voltage

Trekrider2001

Registered
During the power outage yesterday, we had lights dimming repeatedly. Sure I understand that if you throw a new load on the generator, you might see a drop and the lights dim, but there was nothing going on. I even turned the fridge off to see if it was kicking in but that did not change anything. The only thing on was to big screen plasma TV. When I paused the show, the dimming was reduced (not eliminated). I really can't understand that the TV might have such a variable power draw that the generator has a had time following the load. We have a pump in the septic tank, but it is only supposed to come on when the water level is high, then shut off when it gets to the low water setting. It certainly would not be going on and off multiple times per minute. Really, could this be the TV?
 

K-Tron

Registered
Depending on the size of your plasma display, they could take anywhere from 400-700watts each. What is the capacity of your generator? A 3000 watt generator would run the two televisions and the refrigeration without too much trouble, so if your unit is much larger in capacity, something is not quite right with your generator.

Chris
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
I wonder if the voltage regulator is failing, or has a dirty sensitivity adjustment pot...?

Might try adjusting that pot back and forth several times, maybe spray some contact cleaner in it, then set it back to it's original position and see if the problem changes or goes away.
 

Trekrider2001

Registered
Thanks. The generator is about 12 years old and about 280 hrs on the clock. For something that needs to be changed, there is no information on the net on how to change these brushes and where the voltage regulator is. This unit has the ADC controller and the manual has a description on how to control the voltage. I try and check the brushes.
 

Birken Vogt

Email NOT Working
The brushes are in the far end of the generator and you have to take off the roof and sides and an air duct to get to them.

The VR is part of the ADC controller and there is an SCR pack that is the last stage of the VR in the controller box and replaceable although usually it works or it does not.

This is kind of a mysterious problem to diagnose over the internet, unfortunately.
 

Zephyr7

Registered
Do you have a space heater you can use for testing? If so, try running the space heater while you’re on generator. The heater will provide 1500 Watts of almost pure resistive load that will help to swamp any strange issues from your tv load. If the genset is more stable when the heater is added, then you probably have a stability issue (like gain on a speed control).

Bill
 

Trekrider2001

Registered
Like everything else on this generator, its a real pain to service, so before I take it all apart to "clean" the brushes, I might as well order new ones and just replace them. At 12 years on, do you think it is time? How long do brushes last anyway? I have 280 hrs on the machine which does not seem like a lot. The parts web site has a ton of brushes. Now to figure out which is the correct replacement. Not a good idea to have the generator out of service this time of year in the Pacific Northwest. 'Tis the season for power outages.
 

Birken Vogt

Email NOT Working
I almost never replace brushes on these even though some people run them off grid and thousands of hours.

Hours is the only thing that matters to the brushes, age does not harm them.
 

Trekrider2001

Registered
I did the load test with the space heater. I measured the voltage with a digital meter and the voltage jumped around between 120 or so and then down to 100 or so. Obviously, it was not constant. Adding the space heater load caused the voltage to bounce between the high 90's to 119 or so. I turned on the TV to try and simulate the big light flickers of the other night, but I could not. Mild dimming only. Mind you, during the power failure the generator had been running for at least 5 hrs (so very warmed up) while my test today was only about 15 minutes. Birken suggests that the brushes are not worn (not after 280 hrs). Maybe they get dirty or coated? If I take them out how do I clean them? With some emery cloth? What about cleaning the slip ring?
 

Birken Vogt

Email NOT Working
Is the variation rythmic or chaotic?

Using some ideas from the other thread, you might try feeding 24v into the brush circuit and see if it still happens or is stable then.
 

Zephyr7

Registered
The slightly lower voltages seen with the heater running relative to not are probably due to volt drop in wiring. Seems like the generator is causing the problem regardless of the type of connected load.

Might be corrosion in the slip rings, but that should make more of a noise and less of dimming issue (they spin too fast for you to really see the issue in lights). As Birken mentioned, the brushes only care about operating hours, not age. However, long periods of idle time with no running can result in corroded slip rings since the brushes are wiping them clean while running.

Since you’re saying the issue is rhythmic, that sounds like an oscillation to me. Is the frequency changing too (you’d hear this change in the engine if you don’t have a frequency meter), or is the problem related to voltage only?

Have you checked that there are no blocked vents on the regulator (I think this is a propane or natural gas set, correct?)?

Bill
 

Mark Dieckmann

Registered
Do you have an amp meter? I am wondering if the load changes when the voltage drops. How long is the voltage low? Just a second or three? If so then I would suspect a motor or compressor that is not starting and cycling on and off on the overload protector causing excessive amp draw.
 

Trekrider2001

Registered
the drops are a fraction of a second. I will do a controlled load test tomorrow. Basically shut everything off in the house except my space heater. That should give me some better information.

Natural gas. And the thought of fuel starvation crossed my mind, but I had the generator plumbed with its own direct line after I had my meter upgraded to a two pound system. The feed to the house is rated at 750K BTU. The house light fluctuation was worse during the power outage and I thought that with the neighbors also running their generators, the mains might have a problem. Basically, on both sides I have neighbors with natural gas powered systems like mine. But that seems like a stretch.
 

Zephyr7

Registered
If your gas company is ok giving you 2 PSI gas service, then it’s highly unlikely there is a capacity problem on the gas main.

The regulator has a small vent on it that needs to be clear for the regulator to work. Bugs love to build nests in that vent and plug it up. This is a common thing to check on these units, and it’s very easy to fix if clogged. It’s worth checking before digging deeper into the unit.

Bill
 

Trekrider2001

Registered
The gas regulator vents are clear. That would have been too easy. I ran a load test. With all breakers in the house off, (except for the plug I was using to measure things), the generator was putting out 119 - 120 volts. I added the space heater load (+1500 watts) and the voltage dropped to 118 - 119. I added the oven and it dropped to 117. Then I added the TV and the voltage went unstable with drops to 90 volts. There was no real cause and effect that I could re-create. Turning the space heater on and off would not trigger the drop outs. The oven was not on long enough to cycle on and off. So it is clear, as the load increases the voltage becomes unstable. Does this give us a clue as to what is wrong?
 
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