mark300
This unit has been installed for about 10 years without any issues.  I have it set to exercise once a week and it's worked flawlessly so far.  Oil is changed regularly, battery is maintained annually, everything is kept up with.  Two weeks ago it started and then shut off after 30 seconds or so.

Tonight I did some troubleshooting and it's trying to start after it's already running.  It starts fine, no issues at all, but after 10 seconds or so there is a loud click (the starter trying to engage) and then it does it once more before shutting down.  I can feel the starter solenoid pulling in and then releasing, so I know that's what it's trying to do.

I'm looking for guidance about where to start. I reviewed the schematics but don't see a crank sensor or an RPM sensor, so I'm not really sure where to begin to troubleshoot.  Any assistance would be greatly appreciated.

Mark
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Birken Vogt
I did not look up the model number but chances are the AVR failed, it has no AC output and the controller does not realize it is running.
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mark300
On the schematic it looks like the DC VR is what controls the starter solenoid.  The DC VR has only 2 inputs from the DC alternator. I see another VR that appears to be the AC VR, it gets inputs from the generator stators.

Is it the DC VR that I should be looking at?  What should I be expecting on those two inputs - 13.8VDC?
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Peddler
You need to post the SN of the unit.  Different units get there run signal from different places so we need that info so we can figure out what is going on.
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mark300
SN 3844487
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Peddler
No AC output is the problem either the field flash circuit has gone bad or gotten weak or the VR is bad.  In any case this unit gets it's run signal from the AC output and even though it is in fact running the generator doesn't think it is and try's to restart until it faults out on over crank.  Try jumping 12VDC to the 4 wire on the terminal strip and see if the voltage comes up.
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mark300
Thanks.  Just so I understand what I'm doing - it looks like the VR gets its AC input on S15 and S16, and then outputs 12V when there's good voltage, which goes to the control PCB.  So if I have good AC voltage on S15 and S16, but no output on the 4 terminal on the VR/terminal strip, the VR is bad?  Or, if I have good AC and DC on the 4 terminal, the control PCB is bad?
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Birken Vogt
The VR gets its voltage sensing from S15 and S16.  Power on 2 and 6 or 162.  It outputs a variable DC on 4 and 0 (or 1).

The VR is not really connected to the controller other than the controller momentarily applies flash to 4 when starting, and monitors gen. output through sensing wires which may or may not be the same as the VR sensing wires.

To test you rig up an alligator clip from battery hot and start the engine, briefly but firmly apply +12V to wire 4 and see if output comes up.  If it comes up the red VR light may turn on or it may go off again.  It most likely is bad although there are a few other tests to be sure.
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mark300
Following your instructions I started the machine and applied 12V from the battery to 4.  The red light came on the VR and it ran without any issues until I shut it down.  I transferred load, too, and everything worked perfectly.  Is that an indication that the VR is bad?
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BrentB
Would indicate field boost during cranking to be the problem. PCB not flashing field during crank, or something pulling it too low to turn on the AVR.
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Peddler
No, that is an indication that the field flash circuit is bad.  There is a component on the control board which directs 5-8 volts to the 4 wire while the unit is cranking.  Those circuits can go bad or the slip rings are dirty and the high resistance is preventing a good field flash.  I would clean the slip rings and then try to get a voltage measurement on the 4 wire while the unit is cranking.  Sometimes it is helpful to shut the gas off so the unit cranks longer to get a reading on a digital MM.  If you don't have voltage to #4 then you have a couple options.  You can replace the control board or you can install a continuous field flash kit.  Either one usually works fine.
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mark300
Where can I find the slip rings on this machine?  Is this the field flash kit?   https://www.zillerelectric.com/products/generac-0h07850srv-field-boost-upfit-kit
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Peddler
Pretty easy on this one.  The plastic end bell cover comes off by removing 4 screws and the slip rings are right there.  I use some contact cleaner a a scotch brite pad to clean them.
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mark300
Can anyone supply a link to the field flash kit I need?  Thanks.
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MarkJ
Clean the slip rings with a large eraser. that way you won't damage the brass on the rings. The brush harness (#075591) may need to be replaced as well. Be sure to verify that the brushes are lined up on the rings as they should be. You may need to shim with small washers.
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mark300
Thanks for the help all.  Problem solved.  I popped the cover off as Peddler suggested and sprayed CRC contact cleaner on the slip rings.  I wiped it off with a rag and it was good to go.  Before cleaning between 0 and 4 I had 3.6V while cranking.  Once I cleaned the slip rings well I had about 1.2V on 0 and 4 while cranking.  I expected it to go up, not down, but it worked.  Thanks for everyones help!
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Cobranut
mark300 wrote:
Thanks for the help all.  Problem solved.  I popped the cover off as Peddler suggested and sprayed CRC contact cleaner on the slip rings.  I wiped it off with a rag and it was good to go.  Before cleaning between 0 and 4 I had 3.6V while cranking.  Once I cleaned the slip rings well I had about 1.2V on 0 and 4 while cranking.  I expected it to go up, not down, but it worked.  Thanks for everyones help!


The reason the voltage went down after cleaning is it reduced the resistance across the brushes, allowing more current to flow through the field winding and loading the field boost circuit down.
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