Kubota B7100 wiring problems

Russell King

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L185F, Modern Ag Competitor 4’ shredder, Rhino tiller, rear dirt scoop
Jun 17, 2012
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Take the alternator off and have it tested also?
 

BP176

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B7100, Flail, Rotovator, Chipper
Mar 23, 2024
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Norfolk, UK
Ok, so a quick update.

I spoke to the shop in question and the prime candidate was the alternator energiser light.
Wiring was correct either side of it, so I installed a new bulb holder and bulb. Whilst doing this I also installed a new inline fuse holder as the last one was looking tired.
So now, the system is charging, ish! The new charge light flashes more than a strobe system, but the alternator is now pushing 16.8 v into the battery.
I’m not sure if this high voltage is correct, and am concerned that the new electronic module could be faulty.Or do you think the flashing could be a bad earth?
At least things are moving in the right direction.
 

GreensvilleJay

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So you installed a new bulb.... IS it the CORRECT one though !! Confirm the part number of the new bulb is correct for that alternator/regulator.
The voltage seems OK. Run for say 10-15 minutes,turn off, wait 10 minutes then read the battery voltage. Probably 13.2-13.8 ??
Interesting about the alternator upgrade... going from 10 amps to 35 amps, have to wonder IF the wiring is good for 3 1/2 times the current ?
As fo rthe strobe effect. Check and recheck the ground for the regulator and the alternator going to the battery -ve post. if in doubt, replace the wiring.
 

Jim L.

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Jun 18, 2014
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The new charge light flashes more than a strobe system, but the alternator is now pushing 16.8 v into the battery.

16.8 volts will boil out the battery. It should be closer to 14 and something for charging. The charge light flashing says that something is still not shipshape. Connections and terminals need to be clean and in firm contact both positive and negative.

As GreenvilleJay has noted, the bulb needs to be the old incandescent kind, and not an LED.
 

Dave_eng

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Oct 6, 2012
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Have you studied the pages in the b7100 dealing with a larger alternator installation instead of the basic dynamo?
Instead of messing with an external regulator and a 35 amp alternator, to me the hard work is done getting an alternator mounted in lieu of the 10 amp dynamo.
Now consider installing an alternator with internal voltage regulator. There are many models whose form factor i.e. size, will be smaller than the unit you currently have and provide greater output.
Here is a $100 Amazon one with 40 amp output. Don't get carried away with output as you can easily overpower the V belt drive
Alternator
Dave
 

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jaxs

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B1750HST
Jun 22, 2023
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The more I hear,the more this sounds like charades. 16+ v seems high and in addition to possibilities already mentioned, flashing could point to poor/no rectification.
 

BP176

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B7100, Flail, Rotovator, Chipper
Mar 23, 2024
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Norfolk, UK
Hmmm, I can’t seem to add video on here. I have a short clip of the voltage changes(on a multimeter), whilst seeing the pulsing/flickering/strobe light in the background.

with regards to the bulb, have no idea if it’s correct. Probably not, as the original holder was a bayonet type, which was tested with a new correct bulb, and the new bulb holder is a push fit. It still is an incandescent bulb though. The guy in the shop just pulled it out of a drawer and said try this and that will tell you if it’s a bulb holder.

With regards to the earth, I’m tempted to disconnect it from the block, and run it straight to the negitave battery terminal.
is there a way to test the new electronic module?
 

Jim L.

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Jun 18, 2014
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Texas
is there a way to test the new electronic module?

1. Assuming the alternator is functioning properly.
2. Overvoltage may indicate a bad connection. For example, earth. Cable jump around the suspect conductor(s).
3. Perform voltage drop tests to search for bad connections. Current thru a bad connection will create a voltage that can be measured.
4. Likely at this point (voltage is too high) is a bad regulator, assuming that it is wired correctly. Simple to plug in new one. Make sure to disconnect battery when changing it out.

Old bulb had a number, which can be looked up for 12 v and the wattage. You want close to the same watts on the replacement bulb.
 

BP176

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B7100, Flail, Rotovator, Chipper
Mar 23, 2024
12
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1
Norfolk, UK
A further update,

I spent most of the day yesterday trying to sort the issues with the charging system out.
I had spoken to the shop where the starter motor, and alternator had been reconditioned and that had supplied the new electronic module.
They looked at the videos I had taken and diagnosed a faulty regulator and provided me with a new one free of charge.
I also decided to uprate the earthing system, and installed new battery terminals and a extra earth wire from the block to the battery.
The new voltage regulator was fitted.
When I went to start the tractor I put a multi meter on the battery to monitor the voltage.
A charged battery started at 12.8v which dropped to 12.4v during preheat, the charge light was lit all this time.
The battery went back to 12.8v when preheat finished and the charge light went out.
On turnover the battery went down to 10.1v, with the charge light on. Immediately on start up the charge light went out and the battery went up to 14.5v this remained quite steady ranging from 14.3-14.8v.
After approximately 5 minutes with the battery voltage remaining at around
14.5v the charge light came back on in a non regular strobe pattern.
All earths seemed to be working.
In desperation, and not knowing what to do I reconnected the original nippondenso analog regulator.
Through testing this performed flawlessly, and I can only think that the failed charge light that I had no knowledge of caused the original failure of this component?
With 2 of the digital regulators failing, do you think they’ve been getting too hot over the cylinder?
How would you proceed from here, keep as is and try and source a spare original analogue component, or try and work out why the digital ones keep failing?
And ideas much appreciated
 

GreensvilleJay

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BX23-S,57 A-C D-14,58 A-C D-14, 57 A-C D-14,tiller,cults,Millcreek 25G spreader,
Apr 2, 2019
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Greensville,Ontario,Canada
Yes, sounds like 'classic' overheating of solidstate regulator. I went back to the 3 pictures of how it's mounted and YES the new unit WILL selfdestruct from heat, only a matter of a short time.
I make the assumption that the original regulator,back in the 70s, was an electromechanical type( had relay(s) in it ) and was mounted on that rubber pad to absorb vibration.
The electronic one does not require the 'antivirbration' pad but NEEDS a big 'heatsink'. I'd remove the rubber pad, clean any dirt, grease, grime from the area and bolt the regulator to the 'tin work'. If it won't lay 100% flat to it, cut some thick (1/8-1/4") aluminum sheeting to 3by4, 4by6, whatever size fits in the area, bigger and thicker is better. Use the 'pad' as a template for the 5 holes, but make pad as big as possible.
The back of the regulator is metal and needs to be in contact with metal to get rid of the exess power. which could be 60 watts ( 6volts x 10 amps ), similar to a typical 60W incandescent light bulb. You couldn't put your hand on that !
 
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BP176

New member

Equipment
B7100, Flail, Rotovator, Chipper
Mar 23, 2024
12
0
1
Norfolk, UK
Yes, sounds like 'classic' overheating of solidstate regulator. I went back to the 3 pictures of how it's mounted and YES the new unit WILL selfdestruct from heat, only a matter of a short time.
I make the assumption that the original regulator,back in the 70s, was an electromechanical type( had relay(s) in it ) and was mounted on that rubber pad to absorb vibration.
The electronic one does not require the 'antivirbration' pad but NEEDS a big 'heatsink'. I'd remove the rubber pad, clean any dirt, grease, grime from the area and bolt the regulator to the 'tin work'. If it won't lay 100% flat to it, cut some thick (1/8-1/4") aluminum sheeting to 3by4, 4by6, whatever size fits in the area, bigger and thicker is better. Use the 'pad' as a template for the 5 holes, but make pad as big as possible.
The back of the regulator is metal and needs to be in contact with metal to get rid of the exess power. which could be 60 watts ( 6volts x 10 amps ), similar to a typical 60W incandescent light bulb. You couldn't put your hand on that !
Jay
Many thanks for this.
A couple of questions,
I assume that once the regulator has overheated it’s completely toast and will need to be replaced?
I had always assumed that the rubber mounting was to stop the regulator making contact with the negative earthed body, as it was bolted to the rubber and the rubber was separately bolted to the body with the bolt heads that touched the regulator insulated (see picture)
As these new regulators are completely plastic is there any requirement to insulate them as well?
 

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