Another alternator problem

[guest23837]

Hi guys, I bought a yanmar diesel generator 5.7 kw 10hp. Excellent engine but no power. I replaced the brushes still no power when a multimeter is connected. I am getting 4 volts from the outlet socket, any suggestions?

[dieselgman]

Insufficient information provided... But you may need to "flash" your field. Restore magnetism if residual has been lost in storage.

dieselgman

[guest23837]

Hi G-Man The engine is an L100 not sure of the alternator brand it has brushed and an AVR and 110 and 230 v outlets and 12v battery charger. I have read several articles about flashing a generator I'm a little bit afraid of electricity and giants but not many giants in Ireland! Could I blow up the AVR by flashing could I blow up everything? I have a battery charger could I use the 6 volt setting to flash it? Thank you

[EdDee]

Hi JD,

Not to undermine anybody here, but I had a similar problem with my yanmar clone autostart unit... It turned out to be the AVR unit that was kaput... Ordered a few off fleabay and when they arrived, plugged in and tested....

Found 2 things, the first of which was an electrical incompatability issue - there was a plug between the avr and gen with 4 wires going into it - when plugged in and running, there was very low output on the 220V terminals, it turned out that the pairs of wires were switched around, when taking a random stab at things, I switched the pairs around and all came right...

The second was a tricky issue that reared its head after the unit was tested standalone with isolated non-household loads (where it worked perfectly)... It turns out that the AVR, when mounted, had a heat sink sticking out of the potting and was shorted to earth when mounted to the genhead. as soon as N/E was coupled together by the addition of a household load (My N/E is connected at DB Board as well as pole) the slight raise in potential be the earth of the genset, being fed back into the heatsink which wasn't insulated from the control circuitry by the looks of it, caused the output voltage to cycle from about 50 up to 150V at about 5Hz...

Long and the short of it - Has the AVR been replaced? Does it look like a new chinesium one in better condition than the internals on the genset? If so, maybe the pin config on the plug is incorrect. If not, visit fleabay and get a couple.... (Oh, and make sure that the heatsink that sticks out the back of the AVR isnt shorted to ground...)

There are also one or two other 2pin connectors on the genhead proper (Besides the 2xsets of 110v outputs) - they are for auxilliary 12/24v generation to charge onboard starter batteries and provide sometimes a separate 12/24v output, once rectified, for the 12/24v dc outlet...

Cheers
Ed

[guest23837]

Thanks guys! I haven't replaced the AVR yet one has been ordered from Amazon.co.uk. It appears to have been strapped to an especially lazy tortoise but im hoping it will arrive eventually. This generator is another 50 quid buy. The starter motor wasn't working so it was left abandoned, I put in fresh diesel and a pull start and she started soon as the injector popped. I tried the drill idea to flash the alternator but still nothing at the brushes. It is a noisy bugger but Im not too bothered about that. I have just ordered a new brush box for it as well as replacing the brushes again the brush box will probably take a while. Thanks Glort I will try a car battery long as it won't fry ME the alternator can be repaired/replaced! Paul

[mike90045]

When I flash a alternator/generator, I use an old style automotive jump pack and a taillight/stoplight bulb

The stoplight bulb provides a current limiting resistor, and some visual indication you did something, if med-dim. you flashed it
no glow, the winding is open, full bright, something is shorted.  The bulb also can provide some grace against frying the regulator or diode bridge if you hook up wrong.

some ideas
https://www.smokstak.com/forum/showthread.php?t=60336
http://www.dieselduck.info/machine/03%20electricity/flashing_generator.htm

The idea is the diode pack rectifies AC to DC and that is applied to the Field   That's where you attach the DC, at the AC pins of the diode bridge.  The diodes will steer the DC in the proper direction to re-magnetize the field.

In theory.  It works for me.

[guest23837]

When I flash a alternator/generator, I use an old style automotive jump pack and a taillight/stoplight bulb

The stoplight bulb provides a current limiting resistor, and some visual indication you did something, if med-dim. you flashed it
no glow, the winding is open, full bright, something is shorted.  The bulb also can provide some grace against frying the regulator or diode bridge if you hook up wrong.

some ideas
https://www.smokstak.com/forum/showthread.php?t=60336
http://www.dieselduck.info/machine/03%20electricity/flashing_generator.htm

The idea is the diode pack rectifies AC to DC and that is applied to the Field   That's where you attach the DC, at the AC pins of the diode bridge.  The diodes will steer the DC in the proper direction to re-magnetize the field.

In theory.  It works for me.

#
Thank you this suggestion goes well with my idiot knowledge of electrics  simple and obvious!

[quinnbrian]

Just flashed one today...pulled the car up  hooked up the booster cables...disconnected the plus terminal on the rectifier , hooked a wire from the negative battery cable to the negative on the bridge rectifier ( leave the wire hooked up the the rectifier) , started the generator, with the volt meter on the output voltage, held the positive battery cable to the positive terminal the went to the rectifier ( the wire must be unhook from the rectifier...or you will smoke your rectifier) , look at the volt meter...when it gets to 115 volts, disconnect the positive battery cable...you should see a spark come from the end of the battery cable and the positive wire that came off the rectifier ...if you don't...try again!
After you get the "spark"  LOL
Stop the motor, re-hook up the positive wire to the rectifier, and start your motor, power should be as normal again.
Cheers
Brian

[guest23837]

Thanks guys the generator is producing power now! Interestingly when I was trying to figure out what was wrong I watched a video by generator guru. In it she said you disconnect the wires from the brushes on the generator and you should get 4-5 volts from the terminals on the brushes. There was nothing there I assumed it was scrap. Thanks Top Eddee Glort it's now running producing a very steady 235 volts. Lesson learned - youtube videos aren't gospel!

[quinnbrian]

Here is the ST manual I used to reflash my gen head...hope this helps...I didn't know you could reflash, when it wasn't running..have always done it this was...It's on the last page of the manual.
http://cgg1.com/index_htm_files/ST%20Manual-42013.pdf

[38ac]

Won't help you now  but a trick I learned to easily acomplished the  same thing is to simply  plug a single speed electric drill into the receptacle and with the engine running hold the trigger back and spin the drill chuck backwards.

[BruceM]

I've read good reports on the drill method.  Makes sense- it's a brushed DC motor really and excitement of the mains windings will get the harmonic winding hopping too.  The hard part these days is finding one that isn't variable speed, which might not work.