No power from Generator after new Control Board Install

Generac, Guardian, Honeywell, Siemens, Centurion, Watchdog, Bryant, & Carrier Air Cooled Home Standby generator troubleshooting and repair questions
pop326
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Mon Jun 10, 2019 1:03 pm

After Hurricane Maria my 20 kw Guardian wouldn't start. Found out the control board was full of water.
Purchased a new control board and install it. Now generator starts and runs find, but no power.
Checked the brushes they are good shape. Voltage @ generator output wires .02 volts.
What can the problem be??
Chris
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Mon Jun 10, 2019 1:05 pm

What is the serial number of the generator so that I know which model we are talking about?
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pop326
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Mon Jun 10, 2019 1:27 pm

Model:OH4653
Dis: 999.00cc
Serial: 8580324-11266

Also getting a "Under Voltage Error"
Chris
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Mon Jun 10, 2019 2:02 pm

That information is from the engine, there will be a data tag on the black divider panel just by the front door. It will be a larger silver sticker with the model and serial number on there.
Generac tech for over 12 years. I'm here to help!
"The only source of knowledge is experience" -Albert Einstein
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pop326
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Mon Jun 10, 2019 4:22 pm

Sorry about that Chris,
My wife sent me a picture of the wrong sticker.
Model: 0058751
Serial: 6596052
Controller P/N OH6680D REV. J K1729
Software: 0J3401 REV. F
Chris
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Mon Jun 10, 2019 4:24 pm

Ahh, perfect!

What is the brush resistance up at the controller on wires 0 and 4?
Generac tech for over 12 years. I'm here to help!
"The only source of knowledge is experience" -Albert Einstein
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pop326
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Mon Jun 10, 2019 4:47 pm

VM Set on 200 ohms
Wire 0 to ground. .4
Wire 4 to ground. 21.8
Wire 0 to wire 4. 21.6
78buckshot
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Mon Jun 10, 2019 5:59 pm

Hi pop, the resistance across wires 4 and zero are reading about twice the specification that they should be. When you checked the brushes did you clean the slip rings, check resistance from ring to ring, check to see if the brushes were riding on center of the rings? I think the brushes are not centered and we are seeing high resistance through that circuit, the undervoltage can be a direct relation to a brush problem.
pop326
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Sun Jun 16, 2019 9:48 am

Couldn't get back to you sooner, Live in the rain forest and Yeh, it's the rainy season.
But anyway the resistance from ring to ring is
VM Set on 200 ohms. is 10.6
Blue wire to end of brush .3
Black wire to end of brush .3
78buckshot
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Sun Jun 16, 2019 4:36 pm

The ring to ring resistance is good, if you still have the unit torn down at that end you should clean and polish the slip rings before you put it together. We'll go on from there.
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