bhm_to
[B]Model #: Generac 20kW [/B]0055251[B] Serial #: [/B]5465087
[B]Propane or Natural Gas: Propane[/B]
[B]Length of gas pipe feeding the generator: 30 feet.
Size of gas pipe feeding the generator: 3/4"[/B]
[B]How long since the last full maintenance:[/B] [B]1 month[/B]
[B]How long have you experienced this problem: 2 weeks happened twice
Description of problem: [/B]Overspeed error after running for a few hours, low load. I then turn off and back to auto and it continues running.

Tuned up,valves, spark plugs and replaced stator assembly and mixer assembly over a month ago. (another post, had to find expert generac tech to fixed local clown who messed up mixer assembly installation). Starts well and kicks in and starts and runs under load. We have had a few outages this past month.

Any ideas why the generator would run fine for hours and then decide it has overspeed error and shutdown? Should I check anything? Is this not usually the stator/govenor causing this, which has been replaced.
thanks
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Peddler
The speed signal comes from the coils. If in the course of doing this work the #18 wire to the coils is pinched or making intermittent contact it could cause an overspeed fault. Have you personally witnessed this fault?
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78buckshot
bhm, did the unit sound like it was running too fast, do you have a meter to check frequency? Like Peddler asked, did you see and hear it when it faulted?
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bhm_to
Hi
I was asleep when error occurred and shutdown, but during the day earlier I did hear the generator rev high and erratic at least twice but kept on running. in my alarm log I also saw an overspeed error when it appears to have been in the weekly maintenance mode a couple of weeks back with no load.
thanks
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78buckshot
Well then, I'd say you need to ohm the stepper motor, check the harness and connector, check the throttle body and linkage. If all is good in that department then my next suspect would be the controller.
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BrianMartin
Ive seen a few overspeed alarms on the core power units caused by a broken ground wire, might be worth a check.
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bhm_to
After checking what I could the past few days, today on weekly maintenance schedule, over speed alarm almost immediately. Ran in manual mode and stopped after 2 minutes with over speed.

When mixer was replaced I assumed the stepper was replaced but suspect not now. Just checked parts invoice, no new stepper. (certainly looks new). Checked behind the stepper, check the harness and connector, check the throttle body and linkage The linkage behind the stepper I cant even move (the arm). Have ordered a new stepper, doesn't look too complicated to replace. Any hints for replacement will be appreciated.

thanks for responses
brad
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exrace
I had a problem with overspeed after I did the LCD replacement surgery.
Found that the stepper motor connection was plugged in but possibly had a high resistance connection.
Unplugging and plugging the connection a few times fixed the issue and has been stable since.
Hard to say what the tech messed with but possible the intake manifold could be lose and fitted wrong.
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