n9ktw
Hey guys.....

Today the boss brought in a few used generators  he picked up VERY cheaply. 

The one that I am working on is as follows:

MODEL # 0052420

WE got the machine to start, so we know the basic engine is good. Had it running for several minutes, ran smooth  etc. Good enough for testing.

Now to the alternator ...  It makes ONLY "residual" voltage. I took the meter and set it to read HZ, and got 115 Hz. The light on the voltage regulator was NOT lit, and adjusting the pot on it had no effect. 

The output windings showed about 0.3 Ohm "line to neutral" each set..... is this correct?   We didnt ring out any of the other windings, as we didn't have  a service manual. 

Any ideas?  Anyone have a downloadable manual, the internet didnt yield any.....


Howard, N9KTW
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78buckshot
Hi Howard, I think your test meter is lying to you, at 115hz. the unit should have alarmed and shut down on "overspeed", not to mention that the engine would self destruct within seconds due to the connecting rods punching through the crankcase. So on to checking and testing, you need a test meter of high quality and capable of very accurate resistance readings in order to diagnose alternator issues, I'll probably get a little flak from some members but the "go-to" meters that most guys trust are FLUKE. The clamp-on amp meters even from FLUKE are not capable of reading resistance values for the alternator windings. Call Ziller Electric and ask if they can ship a diagnostic repair manual to you, it will give very detailed directions and specs for testing.
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Geoff Z
This is the digital download of your diagnostic manual:  

https://www.zillerelectric.com/products/generac-0g4338-air-cooled-diagnostic-manual-digital-download?_pos=36&_sid=4e43f2f13&_ss=r


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n9ktw
&* and Geoff:

Thank you so far for the help.    I checked the meter  (Greenlee DM330 last known FACTORY calibration 2015) here at home.... frequency was fairly close to 60 Hz , and voltage was acceptable too. I agree that if the engine was at double speed we would have had a serious problem...... It sounded like it was at the right speed. 

The "residual voltage" that I save was about 1.7 V "phase to phase" . I am guessing that this is telling me that the output windings are still good.

I am going to download the manual and start reading it!

IMHO, with the engine running, I am guessing the rotor and slip rings are giving the engine the right signals to keep running, and I either have a voltage regulator or winding issue.... Stop me if I am wrong 🙂


de Howard
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Geoff Z
That is a True RMS meter so you should be good. Always a good idea every so often to check a known voltage and frequency like you did. Just to confirm accuracy. My girls will see your order and process it on Monday morning. With the diagnostic manual and our techs advice you will be on the right track. 
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78buckshot
I have used meters that are True RMS but won't read the frequency at the generator, my suspicion is the RFI from the ignition is sending the meter into a tizzy. Were you checking output voltage at the line side of the MLCB on the generator? It should have alarmed on "undervoltage" if it indeed was not producing correct output.
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Peddler
Those units will run even if the rotor and or stator have problems.  They get there run and speed signal off the coils.  The best test to get an idea if you have an Ok rotor and stator is a fixed voltage excitation test.  Jump 12VDC to the #4 wire and you should get 60 to 90 volts at he breaker L-L.
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n9ktw
Thank You guys for the info! ðŸ˜

Will check the machine next week when I head in to work. 

Presuming the coils ohm out ok, and I get voltage when I do the fixed voltage excitation test, am I looking at a bad voltage regulator?  If the coils ohm out and I dont get voltage, any ideas what is next?

I so want to get this running, as my boss is a great guy, trying to keep me working through all that is going on, and I want to learn how to fix these machines properly. 


Again, thank you for the help so far. 


Howard
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Peddler
Don't worry about the coils you said it runs, I was just pointing out that they send the speed signal not the Rotor and Stator.  When you do the fixed voltage excitation test report back and we'll have a good idea where to go.  While doing that test check the voltage on the #2 and #6 wire which is the excitation winding ( bottom two wires on the VR) this will also guide us to the problem.
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n9ktw
Not wanting to let the"magic smoke" out of anything, when I do the fixed excitation test, should I be applying the voltage with wire 4 connected to the voltage regulator, or disconnected from it? Likewise checking #2 and #6 connected to the regulator or not?

Just want to be sure I am doing everything right 


Howard
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Peddler
Safest and most telling is with the #4 wire disconnected from the VR.  Same with the #2 & #6 wires take them off and do the same read the voltage across them.
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