mjr46
So I decided to fire of manually my moms 4lm38b Dayton 20kw generator with a generac power unit after it has been no run for about 8 months...….I manually start it about that length of time as we don't have it set to auto, it's propane or natural gas, anyway it runs for a minute or two and shuts down and the red fault light comes on, I know it's not due to low coolant or over temp as I can bypass those switches and ones it shuts down it will start back up and do the same again......what I do notice is I hear a clutch like engaugement screech and sometimes when I briefly hear that noise I see a few sparks shoot out of the power unit vent, also just before the shut down I see the volt gauge drop from about 120 to 0 and at the same time the hertz gauge goes from about 51-52 to pegging it off the scale, then about 20 sec later the generator shuts off and fault light is on...…...I don't think it's due to oil pressure as it has plenty of oil and engine runs well.....unit has 60 hrs on it...……..maybe an issue with overspeed due to gauge pegging? what do I do to verify where the problem is?? any help is appreciated!!!! :)
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Cobranut
mjr46;53003 wrote:
So I decided to fire of manually my moms 4lm38b Dayton 20kw generator with a generac power unit after it has been no run for about 8 months...….I manually start it about that length of time as we don't have it set to auto, it's propane or natural gas, anyway it runs for a minute or two and shuts down and the red fault light comes on, I know it's not due to low coolant or over temp as I can bypass those switches and ones it shuts down it will start back up and do the same again......what I do notice is I hear a clutch like engaugement screech and sometimes when I briefly hear that noise I see a few sparks shoot out of the power unit vent, also just before the shut down I see the volt gauge drop from about 120 to 0 and at the same time the hertz gauge goes from about 51-52 to pegging it off the scale, then about 20 sec later the generator shuts off and fault light is on...…...I don't think it's due to oil pressure as it has plenty of oil and engine runs well.....unit has 60 hrs on it...……..maybe an issue with overspeed due to gauge pegging? what do I do to verify where the problem is?? any help is appreciated!!!! :)


The screech and sparks are concerning.
Perhaps a crank position sensor has come loose and is contacting the flywheel.
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mjr46
Cobranut;53006 wrote:
The screech and sparks are concerning.
Perhaps a crank position sensor has come loose and is contacting the flywheel.
No, I don't think so.........it sounds like a cycling clutch on an a/c system engaging and disengaging every so often.......The loss of voltage and maxing of the Hertz gauge is my concern with maybe what's causing the shutdown?? Although the screech does concern me a little.
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Cobranut
I'm not a generator expert, but I cannot think of anything on a genset that should make a sound even remotely like that, much less any visible sparks.

Good luck with your diagnosis.
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Peddler
Those generators use AC output as the signal that it is running, if the AC output stops the starter is engaged and there is sparks and a bad sound. You need to find out why it is stopping putting out AC. My guess is the DPE breaker is opening but Why. Could be a bad voltage regulator or dirty brushes. You need to solve the loss of AC don't worry about the others. The unit will keep trying to restart for at least 3 times so it will go on for a while.
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mjr46
Peddler;53012 wrote:
Those generators use AC output as the signal that it is running, if the AC output stops the starter is engaged and there is sparks and a bad sound. You need to find out why it is stopping putting out AC. My guess is the DPE breaker is opening but Why. Could be a bad voltage regulator or dirty brushes. You need to solve the loss of AC don't worry about the others. The unit will keep trying to restart for at least 3 times so it will go on for a while.
what do you mean the unit will keep trying to restart? I don't have the unit set to auto mode, just manual......also how and where do I check for a loss of ac signal?
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78buckshot
Peddler is on the right path, the noise is the starter re-engaging because the control is not reading AC output voltage and thinks the unit is not running. Turn off the big circuit breaker at the machine and check for output voltage on the generator side of the breaker as the unit is running, should see 235-245 volts leg to leg and half of that from each leg to neutral. if the reading is unstable or no voltage you'll need to diagnose further.
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mjr46
Guys, i'm still having issues with this/ not fixed....power went out at my moms tonight and i knew the generator was not fixed and i still fired it up and usually it shuts down within a minute, however this time after not having been run in a year it started and the ac voltage and frequency gauges /readings looked fine so we threw the transfer switch and to my surprise all worked well for 10 minutes, then i noticed the garage lights got brighter for a second then went dim, then out = lost my power output, then after that a minute or so the motor shut down an the red fault light was on, i waited a minute and then started it back up and noticed my ac voltage was at 0 and frequency gauge was maxed out and of course no power out put.........could this be a bad voltage regulator?  if so where is it located?   it is a dayton 4lm38b  generator with a generac power unit    any help is appreciated,  we can't get anyone out to look at much less call us back.....i'm a fully certified auto tech so with some guidance i know i can diagnose this, any help is appreciated!!
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78buckshot
Here are some things that could be the issue. Slip rings and brushes need cleaning and checking for correct wear pattern, voltage regulator dropping out after it warms up a little, DPE circuit breaker making and breaking(auto re-set breaker) due to age or overload, stator and/or rotor windings damaged. If you are going to tackle this yourself you need to get a diagnostic manual for the unit or at least a similar machine. Call Ziller and talk to Geoff, tell him as much info as you have about the age, model #, serial #, engine make, RPM, and describe the control panel. It sounds like something from 2004 or older.
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mjr46
it was bought in 1999.............has 100 hrs use, sits most of the time/not used.
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mjr46
78buckshot wrote:
Here are some things that could be the issue. Slip rings and brushes need cleaning and checking for correct wear pattern, voltage regulator dropping out after it warms up a little, DPE circuit breaker making and breaking(auto re-set breaker) due to age or overload, stator and/or rotor windings damaged. If you are going to tackle this yourself you need to get a diagnostic manual for the unit or at least a similar machine. Call Ziller and talk to Geoff, tell him as much info as you have about the age, model #, serial #, engine make, RPM, and describe the control panel. It sounds like something from 2004 or older.
spoke with geoff....he doesn't do tech...just parts........getting parts is not my issue......knowing what to get is:.........model number is 4lm38b = dayton generator with a generac stator.rotoe assembly.....guys if you google that model a manual will come up with wiring diagrams and all and you can see what i have   serial no is 3098257   ..........so i'm right back where i was.....with a busted azz useless generator no one can seem to fix......question is how and what do i start to test???   i will fix this!!!
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mjr46
tonight i'm gonna locate the field circuit breaker and see if that is going to open thus stopping the voltage    this generator has a main circuit breaker= didn't appear to trip as it's on the panel and a field circuit breaker behind the panel that i'll need to remove to access........if the generator starts up and runs and produces voltage like it did for 10 min last night, then i'll know it could be this field circuit breaker tripping and when it trips i'll test it for a open....and if it is open, i'll know half of why it's not working.....it is self resetting so it should be reset by now if that's the case.......question will be if that is what is going on.....what is causing the breaker to trip?     guys i'm a fully certified auto tech so i can deductively reason and troubleshoot if i understand a system/operation....so this is where i need your guidance as i don't normally troubleshoot this type of circuitry.
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Geoff Z
I spoke with mjr46. We determined the serial number. This unit does not come up in GenService. I'm certain because of age. We did a test and put in the voltage regulator part number. It did come up. He does have a manual for the generator. I should have asked for the part number of that. Maybe it could be found. On the very back of the book at the bottom there should be a part number. Post that number we can look it up and see. Post the serial number as well.
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mjr46
form 5s4170  here is a link:   it states it's for a 4lm38c   which is basically the same as what i have ...having looked through it and the diagrams
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mjr46
http://generatorparts.net/tmp/0E48B20Bd01.PDF
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Geoff Z
That is good information and will help our techs know what they are advising on. 
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mjr46
Geoff Z wrote:
That is good information and will help our techs know what they are advising on. 
thanks for the help geoff!! 🙂
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78buckshot
I can't help but think that the stator and rotor windings have been compromised due to moisture. The weekly exercise is in part designed to keep warm air flowing over the windings to drive out moisture. If the windings are not dry and they are put under a load it creates steam in the insulation, the steam pressure breaks down the insulation between the wires in the windings and you end up with shorted windings. You can try a new excitation breaker and see if it holds but leave the main breaker in the off position so as not to load the alternator, diagnostic books have a detailed procedure for drying the windings with several hours of running UNLOADED and a source of heat to warm the air.
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mjr46
78buckshot wrote:
I can't help but think that the stator and rotor windings have been compromised due to moisture. The weekly exercise is in part designed to keep warm air flowing over the windings to drive out moisture. If the windings are not dry and they are put under a load it creates steam in the insulation, the steam pressure breaks down the insulation between the wires in the windings and you end up with shorted windings. You can try a new excitation breaker and see if it holds but leave the main breaker in the off position so as not to load the alternator, diagnostic books have a detailed procedure for drying the windings with several hours of running UNLOADED and a source of heat to warm the air.
this was not the case.......I found another forum with a knowledgable tech who helped me troubleshoot the issue......long story short dirty brushes and slip rings causing excessive resistance led to AVR overworking/heating......so cleaned slip rings and brushes....got resistance to within spec and now waiting on a new AVR to arrive.    will post update when new part gets here and installed.
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Geoff Z
78buckshot wrote:
Here are some things that could be the issue. Slip rings and brushes need cleaning and checking for correct wear pattern, voltage regulator dropping out after it warms up a little, DPE circuit breaker making and breaking(auto re-set breaker) due to age or overload, stator and/or rotor windings damaged. If you are going to tackle this yourself you need to get a diagnostic manual for the unit or at least a similar machine. Call Ziller and talk to Geoff, tell him as much info as you have about the age, model #, serial #, engine make, RPM, and describe the control panel. It sounds like something from 2004 or older.


Glad you got it fixed. If you recall 78 buckshot had already pointed out those very issues. 
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78buckshot
mjr46, I hope for your mother's sake that the AVR and Field Boost Kit get the unit back to a usable condition. Please take our advise as we give it graciously and we love to see success for those that seek help. If the machine responds well with the new components I would keep in mind that it has not had a chance to warm and dry the alternator windings. If it see's a heavy load with damp windings it will do more damage, it would be to her advantage to set the unit up for weekly exercise. As she gets used to hearing it each week it also is helping to keep the unit ready for emergency service and if it fails to exercise on any given week you could respond to her needs with a better understanding of it's fault. Good luck.
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mjr46
78buckshot wrote:
mjr46, I hope for your mother's sake that the AVR and Field Boost Kit get the unit back to a usable condition. Please take our advise as we give it graciously and we love to see success for those that seek help. If the machine responds well with the new components I would keep in mind that it has not had a chance to warm and dry the alternator windings. If it see's a heavy load with damp windings it will do more damage, it would be to her advantage to set the unit up for weekly exercise. As she gets used to hearing it each week it also is helping to keep the unit ready for emergency service and if it fails to exercise on any given week you could respond to her needs with a better understanding of it's fault. Good luck.
thanks for the advice.......i doubt the windings are damp in this unit, it is encased in a boxed unit and is under a large overhang/equipment shed, so unit never gets rained on ever, and i do realize moisture in air and humidity can affect/create what you describe..........in the past for 15 years it has never been an issue as i'm over there weekly and ran the unit/cycled it often while doing yard work for her which is where a lot of the run time has come from.....when the issue occurred 2 years ago, that was the first time it has ever had problems......once i install the new parts i'll make sure it runs for a while to dry out any potential moisture.......i know this thing needs a lot more general maintenence as well, it just has been difficult to get to it with all that is on my plate!!    thanks for all the pointers guys!!
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