Not charging - Kubota B7000

[Nuno Barros]

Hi. Just bought an old Kubota B7000. Had to buy a new battery has came without it. Just checked there's no voltage above 12,5 with engine running, meaning there's no dynamo/alternator working. Or cabling or regulator, I guess. I have multimeter and can see 3 wires, white, brown and yellow coming out of stator place. Can you please help me troubleshoot this? Dont want to use it and kill the new battery
Thanks in advance

 

[fried1765]

Hi. Just bought an old Kubota B7000. Had to buy a new battery has came without it. Just checked there's no voltage above 12,5 with engine running, meaning there's no dynamo/alternator working. Or cabling or regulator, I guess. I have multimeter and can see 3 wires, white, brown and yellow coming out of stator place. Can you please help me troubleshoot this? Dont want to use it and kill the new battery
Thanks in advance

While your tractor is shut down, keep a small "maintenance charger" connected to your battery, until you get the dynamo/alternator issue sorted out

 

[Nuno Barros]

While your tractor is shut down, keep a small "maintenance charger" connected to your battery, until you get the dynamo/alternator issue sorted out

Yes, sure, have done it. Battery was taken out and directly to maintenance charger
Thanks

 

[GreensvilleJay]

Since you don't KNOW why it isn't charging disconnect the battery ground when not in use.
Connecting a charger/maintainer without disconnecting the battery ground may not actually charge the battery and may introduce additional problems .
Find a good copy of the wiring diagram ( in the WSM..) before trouble shooting.
Most 'electrical' problems are easy to fix ONCE you KNOW what you're looking at. What I don't know is IF the wiring is original, what type of charging system it has, any 'modifications' or 'additions' to the machine.

 

[Nuno Barros]

I believe its original wiring. Lamps are not working but not important unless causes issues with battery not charging. And found one fuse box (I can see 2) without fuse. Could it be related? Thanks

 

[GreensvilleJay]

tractordata says B7000 is early 70's.....
if so , probably a 'dynamo- rect/reg' charging system ??
real simple.
Missing fuse is a clue !
Dynamo should (may ?) have 2 same coloured wires coming from it. Will produce about 30 volts AC @ 1500 RPM +-. if you get that, it's good...
Rectifer/regulator is similar to classic B&S small engine units. Put AC in, get DC out.
Be sure there's a good ground from unit to battery.
try Google for proper/correct wiring.honestly with that , it's 10 minutes to fix, without, 10 dayze....

 

[GreensvilleJay]

curious, searched here, saw an earlier post that said B6000 wiring is same as B7000. if so B6000 WSM is in www.kubotabooks.com website, free ! Kinda rough but readable, hopefully will help you.

 

[Dave_eng]

curious, searched here, saw an earlier post that said B6000 wiring is same as B7000. if so B6000 WSM is in www.kubotabooks.com website, free ! Kinda rough but readable, hopefully will help you.

Just an old memory that may be relevant. If there are three wires coming from the dynamo then this system is a bit more complicated than say a B7100.

With the 3 wire system, using two of the three wires the headlights are powered by an alternating current voltage using two of the three wires. The remaining pair of wires go through the rectifier to charge the battery.

If the owner can post some photos of the dynamo and rectifier I may be able to find a relevant wiring diagram. These systems were a problem for owners who switched their headlights to LED which then would not work because the Alternating Voltage current. Their headlight brightness would change a lot with engine speed as the faster the dynamo rotated the higher the voltage sent to the headlights.

Dave

 

[Dustball]

Many alternators require the dash charging lamp to be functional.

I'd start by changing the bulb since that's an extremely easy and cheap repair.

 

[GreensvilleJay]

agree 'picture is worth 1000 words', might even reduce the number of 4 letter ones too !!!
Old stuff is simple stuff...only a few wires, couple of fuses,....no computers, NO CANbus !

 

[Dave_eng]

Just an old memory that may be relevant. If there are three wires coming from the dynamo then this system is a bit more complicated than say a B7100.

With the 3 wire system, using two of the three wires the headlights are powered by an alternating current voltage using two of the three wires. The remaining pair of wires go through the rectifier to charge the battery.

If the owner can post some photos of the dynamo and rectifier I may be able to find a relevant wiring diagram. These systems were a problem for owners who switched their headlights to LED which then would not work because the Alternating Voltage current. Their headlight brightness would change a lot with engine speed as the faster the dynamo rotated the higher the voltage sent to the headlights.

Dave

I found two wiring diagrams for Kubotas with 3 wire dynamo's. The colored lines are mine on top of the black lines.

For Dustball's info: Old style Kubota dynamo's did not use nor have a charge warning light. That feature was added in later years.

Dave

 

[Nuno Barros]

Hi all, thanks for your replies.
Already helped even I've red those now. Not sure I wrote this before. This is very used and bought it some weeks ago. No experience with trators

Well, it's B7000, and I've found wiring diagram. It's B6000 but similar the same 100%.

Yes, I believe the lights (Which does not run, wires are cut when going to the bonnet) works with AC or else does not makes sense to me that 2 wires from AC generator goes lights switch. Confirmed with post above also, thanks. Not important for not to fix the lights, but who knows in future...

Been testing and found the fowlling:
- 3 wires from dynamo/alternator: brown with yellow (or white) gives AC power from 5v to ~20 with high RPM
- checked conductivity from brown to rectifier, and yellow and white to light swtich - all Ok
- wire from B on rectifier (RED in diagram, 0.85) to Main Switch, which I believe should give DC current/voltage to charge baterry, is BURNET A LOT, even cut in the middle.....basically somewhere in time this got burned...WHY??!? Well.... being dynamo given AC voltage, wires from alternator were connected according to electrical diagram, so I thought I should measure the that burned wire coming out from rectifier, looking for DC voltage around 13,5-14 I guess.... I measured it and it's like 11,5 volts idle, but once rpm grows up voltage gets to 25volts....in DC.... Well, have not fixed the that wire going to Main Switch (and Battery) and I guess I understood why that wire from rectifier to Main Switch bot burned.

NOT NORMAL to have 11,5 to 25+ volts, right?
Are those output from alternator as expected? Is it a faulty rectifier?c
Also I've made all these tests with Lights Switch in 0 (off) position... not really sure if that would make any difference being 2 from the 3 wires from dynamo/alternator goes to Light Swtich.

Thanks in advance for your advices
BR/Nuno

 

[GreensvilleJay]

according to the diagram... light switch must be in '1' or '2' , to connect dynamo to regulator,to charge the
battery.

it'd be nice to see the actual inside wiring of the dynamo, but I suspect a low current wire of AC for the lights, and two higher current AC wires to charge the battery.

 

[Nuno Barros]

according to the diagram... light switch must be in '1' or '2' , to connect dynamo to regulator,to charge the
battery.

Nuno: Yes, truth....but in my case with Lights Switch Off, I could still get DC voltage coming out of rectifier...and worst: up to 20+ volts


it'd be nice to see the actual inside wiring of the dynamo, but I suspect a low current wire of AC for the lights, and two higher current AC wires to charge the battery.

Nuno: I'm not AC expert but seems to me there 2 different AC circuits, one is used for AC lights and both are used in series for charging battery.

Not sure if someone can confirm it's normal to have such AC values coming out from dynamo and at the end I should have to replace a faulty Rectifier...

 

[GreensvilleJay]

Remove the 2 wires on the rectifier/regulator module that are marked AC, attach DVM, set to AC volts on them. Run engine. Meter will read from say 10 to 30 volts AC from idle to high throttle. Now you could get 8 to 40, 10 to 35....but the voltage will increase with RPM. Dynamos are a spinning magnet inside a coil of wire, really reliable !
The rectifier-regulator(R-R) is probably based on the '70s B&S patent, consists of 2 power diodes,an SCR, zener diode and a resistor or 2. Rugged and reliable BUT can fail when 1) it loses it's ground connection to the battery or 2) fuse is replaced with a higher one or wiring is 'compromised'. In the good old days, I'd repair the R-R, usually SCR blows up...but today you can get them for $20.
Odds are the R-R is defective, or the wiring, dynamos are tough ! Be 100% sure the ground(black wire ? ) IS connected to the -ve of the battery. Any corrosion between them can/will make the R-R not 'operate within normal parameters'.
It'd be nice to have someone 'ring out' the dynamo's 3 wires and case to see HOW it is wired.Rather curious about that.

 

[Dave_eng]

Hi all, thanks for your replies.
Already helped even I've red those now. Not sure I wrote this before. This is very used and bought it some weeks ago. No experience with trators

Well, it's B7000, and I've found wiring diagram. It's B6000 but similar the same 100%.

View attachment 119747


Yes, I believe the lights (Which does not run, wires are cut when going to the bonnet) works with AC or else does not makes sense to me that 2 wires from AC generator goes lights switch. Confirmed with post above also, thanks. Not important for not to fix the lights, but who knows in future...

Been testing and found the fowlling:
- 3 wires from dynamo/alternator: brown with yellow (or white) gives AC power from 5v to ~20 with high RPM
- checked conductivity from brown to rectifier, and yellow and white to light swtich - all Ok
- wire from B on rectifier (RED in diagram, 0.85) to Main Switch, which I believe should give DC current/voltage to charge baterry, is BURNET A LOT, even cut in the middle.....basically somewhere in time this got burned...WHY??!? Well.... being dynamo given AC voltage, wires from alternator were connected according to electrical diagram, so I thought I should measure the that burned wire coming out from rectifier, looking for DC voltage around 13,5-14 I guess.... I measured it and it's like 11,5 volts idle, but once rpm grows up voltage gets to 25volts....in DC.... Well, have not fixed the that wire going to Main Switch (and Battery) and I guess I understood why that wire from rectifier to Main Switch bot burned.

NOT NORMAL to have 11,5 to 25+ volts, right?
Are those output from alternator as expected? Is it a faulty rectifier?c
Also I've made all these tests with Lights Switch in 0 (off) position... not really sure if that would make any difference being 2 from the 3 wires from dynamo/alternator goes to Light Swtich.

Thanks in advance for your advices
BR/Nuno

The checking out AC output from all three dynamo wires need to be done with the dynamo disconnected.
The pair feeding the headlights may or likely will be a lower AC value because it is output to simple light bulbs.
The pair feeding the rectifier will be the higher value found in WSM. Testing to be done at full engine speed.
Dynamos rarely fail. Rectifiers do fail.

Dave

 

[GreensvilleJay]

I found the b6000 WSM and the 'rectifier' IS just 4 diodes, aka 'full wave bridge' so NOT a regulator. as such voltage will vary based upon RPM. Dynamo is 90W ,so about 6 amps( explains the 5A fuse).

 

[Nuno Barros]

Thanks for the replies

1) The checking out of AC outputs from dynamo/alternator I gave above were taken with the 3 wires disconnected. Brown with Yellow and Brown with White gives AC around 5v in idle to 20v full throttle, in each. So I imagine, if I measure both AC inputs of R-R those values will get the double because one is Brown coming Dynamo and another is both Yellow and White coming from Light Switch together (according to Wiring, S + G2 on the Light Switch)
2) if as @GreensvilleJay says is correct, this is not a regulator, that would explain the regulator measuring 25volts DC under full throttle? If yes, then there's no issue with it? BUT...then issue is: how would a battery survive to that? Maximum I believe we should carry into a battery is 15volts DC... I'm running a new Varta battery, don't want to kill it. Unless in old times, older batteries handles such amount of voltage? Ah...please don' forget, I bought this like it is and wire from R-R to Main Switch to deliver charge power to battery was completely burned...I guess it means something, if for instance I've tried to remake that wire and connected it with my new battery before measure the DC voltage I woulkd lost the battery and maybe cause a short circuit
3) There's no fuse in the R-R and dynamo + Battery circuit, I guess. Check wire diagram above. The fuse I was talking about before it's for the horn...not working as the lights, but not important
4) The ground wire to R-R is not directly to negative pole of battery but to the rear of instrument panel. Somehow this is also connected I guess to negative pole of battery.

Since it's an old stuff, yes there's a bit of rust on connections.... but also from what I'm concluding from point 2) does the dynamo and R-R is working as expected? Would it make sense to try to redo the burned wire and connect it from R-R DC output to Main Switch, which then goes to Battery?

Thanks mates

 

[GreensvilleJay]

I printed out the schematic and may have made sense of it....
The dynamo can be though of as a 'center tapped' transformer, with White being the center tap between the Yellow and Brown 'ends' of the transfomer. Wht, the center tap, goes to the 'B' terminal of the headlight switch and connects to 'T' that then feeds +ve 1/2wave DC to the headlights when in '1' or '2'.
Yellow goes to the 'G2' terminal of the HL switch, connects to 'S' terminal that goes to a 'bridge rectifier'. The Brown goes to the other AC side of the bridge.There's a ground wire from the bridge as well as the '+12 volt' output that connects to ignition switch, starter and battery.
Sadly there is NO fuse between the rectifier and the battery. Should be a 10 amp for 'safety' !
NO voltage regulation, just full wave DC to the battery WHEN the light switch is on '1' or '2'.
What I don't know is IF that 'headlight' switch has resistors that limit current, similar to old tractors where generator field current was roughly controlled.
I'd have to have one of those switches to test and see.

 

[Nuno Barros]

Not sure inside Dynamo but there are some connections not as you say, and also not according to wiring diagram.
Actually White goes to G2 in Light Switch and Yellow goes to S, which is also connected to AC input to R-R. The brown yes goes to other AC input in R-R.
Light Switch:
Off : I believe some AC voltage will go to Rectifier because Yellow (yellow to S and S to R-R) and Brown is connected to it. Explains maybe why I see DC charging current coming from the 2 output wires from R-R
On - 1 or 2:
S + G2: meaning not only AC from Yellow but together AC from White goes to R-R
B + T: meaning AC power will be sent to Head Lights

Makes sense it works like this according to what I read from wiring diagram and from the tests I made. After checking my sentences above, does everyone agrees with my findings?

The strange part would be this R-R is not a voltage regulator, just a rectifier, because as such that would not be healthy for batteries. I've been looking for this part with P/N: 66611‑55250 (taken from parts list in manual) in the internet, and usually it's being sold not only as Rectifier but also Regulator, check below:

Also this post shows that it should give only 13,5 volts as it happened when this case got fixed with new R-R:

Dynamo - B7001 - low voltage - what to do?

Thanks Dave, https://www.ebay.co.uk/itm/12V-Voltage-Regulator-For-Kubota-Tractor-B7100D-B7100HST-D-B7100HSTE-/181882287967 This is the unit I've got, three wires and a ground, I'd appreciate any help you can offer, will test the machine tomorrow. See the marked up photo of the rectifier...

www.orangetractortalks.com

Couldn't it be my R-R is burned and needs replacing, and not controlling what it delivers to Output wire?

Also I read that inverting battery polarity can kill the diodes inside the R-R. Maybe that explains why wire from R-R output which used to be White was burned a lot.

Thanks in advance
BR/Nuno