Cepdave
Hello All,

My 40KW liquid cooled generator (Model #QT04039AVSN) has been running good for several years but has developed a couple new problems which I think are unrelated.

Last weekend I changed the battery. This weekend during the test cycle, I thought I heard it rev up and shut down. When I went out to look, the overspeed light was solid red. I decided this might be a good time to run it through a full load test just to make sure everything was okay. It ran good for about 5 minutes then surged several times and shut down. Any ideas??? 

Just for some history, this generator did have a problem with the butterfly choke. Actually several times. I finally gave up and replaced it with a brand new one I purchased from Ziller about a year ago.

The second problem.

For the past month, it seems as though the generator has been running rough. The engine seems to be running find but it seems like something is out of balance. When I put my hand on the electric motor part, it feels like it's vibrating. It feels exactly like something is out of balance. It also sounds like there is a rattle. It almost sounds like there is a small piece of metal bouncing around in the area the the air comes out. I'm terrified that this could be a serious problem. On the other hand, I'm not positive it hasn't always been this way and maybe I'm worrying about nothing. 

I really want to get ahead of this because this isn't the kind of thing I want to run until it really breaks.  I'm really hoping this is all minor stuff that can be fixed relatively easily. I do travel often so it does need to be 100% perfect all the time. I guess that's why we have these things.   🙂

I'm happy to take a video if that's of any help.

I look forward to all the great advice I always get from this website.

Thanks again in advance!
David
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Cepdave
493BF270-9A0C-4521-B625-0517BCAC08F7.jpeg  5829FB92-06DF-4431-9896-149E664A01F1.jpeg 
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Cepdave
I took a look at the cooling fan on the alternator and can see some damage to the blades.
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Cobranut
Something is bouncing around in there.  I wouldn't start it again until I found and removed the foreign material. 
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Cepdave
I decided to take a closer look to see if I could see anything inside the fan of the alternator. I felt along the bottom and sure enough, there was a caphead screw sitting at the bottom of the housing. 

I took the starter off to see if I could get it out. I rotated the flywheel all the way around to see if maybe one of the screws had fallen out. None were missing. While rotating the flywheel, I noticed a small crack in the flex plate.

cid-CE6FEB68-C49D-4235-A427-5145011B7028.jpg 

I decided to pull the alternator off to inspect the problem and found the flex plate was completely trashed.

cid-C5FC936A-913E-4CE6-843A-19881E9F2877.jpg 
I'm guessing the mag pickup is also trashed as it looks like it's made contact with the flywheel teeth.

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Cepdave
cid-7198ED36-DD62-4E92-8D39-34A0722545C5.jpg   

The screw I found in the bottom of the housing was the same as the screws used to hold the flex plate to the flywheel and the fan to the flywheel. None of those were missing. Any ideas?

Now the BIG QUESTION!!!! Is the damaged flex plate the cause of the vibration problem or the result of the vibration problem???? HELP!!!!

Thanks again for all your support!!!!!
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Cobranut
Ouch.  Good thing you tore that down now.  You were one start away from a major catastrophe.
The loose screw could've been there since it was new, but finally rattled its way into a tight spot.
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Peddler


I have seen this before and it is almost certainly a result of a failed flex plate.  At one time Generac was going around the country changing flex plates but this model may not have been included in that recall.  In your first picture the generator can is pulled back at the top of the engine housing/bell housing which would indicate it was not seated or the tie bolts were loose but this may have been after you had started to tear it apart.  I would replace the fan, the flex plate and clean the mag pick up.  You should get all the torque specs and loc-tight all the bolts on the flex plate.
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78buckshot
Given your ability you may as well order new parts and reassemble it. My bet is the bolt started the problem and led to the flex plate failure.
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Cepdave
Peddler wrote:


I have seen this before and it is almost certainly a result of a failed flex plate.  At one time Generac was going around the country changing flex plates but this model may not have been included in that recall.  In your first picture the generator can is pulled back at the top of the engine housing/bell housing which would indicate it was not seated or the tie bolts were loose but this may have been after you had started to tear it apart.  I would replace the fan, the flex plate and clean the mag pick up.  You should get all the torque specs and loc-tight all the bolts on the flex plate.


This picture was taken BEFORE I started to disassemble. I'm guessing this means the can was loose, and out of alignment, which in turn caused the flex plate failure.

The fan looks like a real PITA to replace. What's the procedure for pulling the flywheel off the armature shaft? I have the armature and stator partially separated and don't look forward to taking it all the way apart nor putting it back together. I'm worried I will somehow cause damage when doing this. It's not that I can't,,,, I just don't want to.   🙂
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Cepdave
Just a quick update. I ordered the part from Ziller, but ordered the wrong part. They were able to get me the correct part quickly. Thank you Ziller!

I have come to the conclusion that the bolt that was sitting inside the bottom of the alternator was overall insignificant and wasn't the source of the pinging noise. I conclude it was dropped there most likely when the generator was serviced at some point. I say this because I dropped the fist bolt I installed and it fell in the exact same place. It literally took me an hour to fish it out. I'm guessing someone just gave up on it and left it there. 

I heard the exact same noise while bolting the alternator to the flex plate. I'm now positive the tinny, pinging noise was the flex plate moving around as it started to fail. If you ever notice your generator is making a tinny pinging noise and seems to be out of balance.... shut it down immediately! As someone said earlier, I was one start away from total disaster. The flex plate literally fell apart into two pieces when I removed it from the crank shaft.

It started right up and is purring again. No more vibration, no more strange noises. I ran it for 15 minutes at full load and it didn't skip a beat. I couldn't be happier. I also changed the oil since I had to take the oil filter off to remove one of the screws that holds the alternator housing to the motor.

As always, thank you to everyone who contributed. A special thanks to Ziller for getting me the parts quickly. 

BTW.... this was a BIG job!!!! I have been a gearhead since before I could drive and I have all the tools on hand to tackle this kind of thing. I would say this is not a DIY project for most people!

Thanks again and Cheers!!!
David

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Geoff Z
Thank you for the update. It is always nice to hear success stories!
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Cobranut
Glad you caught it in time, if only just.
Good job getting it fixed.  It does look like a tight spot to work in, and those generator parts are HEAVY.
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Cepdave
It was super tight and extremely heavy. I had to pull a lot of parts off to get at it. I used my engine hoist to lift and move the alternator, which worked well. Now my hoist is stuck in the snow next to the generator until spring.  🙂
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78buckshot
Wheel your torches out there and thaw the ice, gotta' get the tools back in the shop!
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