82 B7100D positive ground ?

[Les]

I bought this old girl at the end of summer primarily for spreading gravel and some snow work on my 1 acre, well and it was orange. While doing initial maint before using her I made a mental note that this was a positive ground electrical system, no red flags just noted it.
Few weeks later after having tended to driveway maint I was trying to get some of the electrical mess cleaned up I pulled out the wiring diagram which shows it to be a negative ground ???
It was tough not to try it the other way but I put it back together the way it was. I verified the battery was not mis marked the + terminal is positive and connected to bolt on transmission, the battery stays charged and starts ok.
I'm confused seems to me the starter and charging system wouldn't like it being hooked up wrong.
anyone have any thoughts on this?

 

[Les]

Thanks Vic, that clears it up for me don't know how or why it got that way but I'm going to make it right.

 

[ibnxe]

Before you change the polarity if the tractor, I would check with an expert or find a correct wiring diagram.
There is one component that IS polarity sensitive, that being the voltage regulator/rectifier. The dynamo actually puts out alternating current, which is converted to direct current by the regulator/rectifier. Reversing the battery connection could fry this item, at a cost of about $80.
I noticed that the parts catalog lists a new and old type B7100D. Do you know what one you have? I would carefully check that the wiring diagram you referenced, is correct for the year/serial number of your tractor.

 

[Les]

That is the same diagram as my book, can't seem to find any info on a Kubota using positive ground.

 

[Greg]

Les there is no Kubota tractor that operates with a positive ground, except yours.

I'm not a Kubota repair expert so you may have to search around a little to find that postive ground wiring diagram.

Gee, and all this time Vic i have been taking your word as gospel!:

 

[Les]

Les there is no Kubota tractor that operates with a positive ground, except yours.

I'm not a Kubota repair expert so you may have to search around a little to find that postive ground wiring diagram.

It's official the positive ground Kubota is now extinct.
I changed connections from the battery to be neg ground and all is well.
Thanks to Vic
Right on all counts! starter turns the same direction, sun sets in the west etc etc. and thanks for the wiring diagram which had the 3 wire dynamo and rectifier where my book showed 2 wire with regulator.

 

[traildust]

Les there is no Kubota tractor that operates with a positive ground, except yours.

I'm not a Kubota repair expert so you may have to search around a little to find that postive ground wiring diagram.

I think you being just a little humble. You the man Vic!

Scott

 

[JosephGozo]

hello

I am in the quest of installing an ammeter in the circuit of a B7001.
The dynamo looks to be a 3 wire item. so matches the file found in this section.

Am i correct in thinking that i should install the ammeter in a series manner on the wire that leaves terminal no 30 on key switch (dark wire - constant flow) and connects to the starter motor's terminal (wire labelled as AV3R) i had a go at the workshop manual and it states the dynamo/rectifier should produce 8 1/2 amps of charging power, so a 12-0-12 ammeter should be fine?

Wiring on tractor is pretty much standard i only installed a rear work light using one of the fuses available for the indicators i think.

(am i right in assuming an ammeter is better than a volt meter to diagnose charging? )

joseph

 

[Tooljunkie]

I use volts before amps anytime. Will indicate a failing regulator generator and a weak battery. Ammeters that interrupt the nornal flow of current (series wired) is adding two connections that can potentially fail. Voltmeter is not intrusive to electrical system.

 

[Russell King]

Ammeters can be more dangerous than volt meters depending on how you wire it. Most were wired so a lot of amperage has to go through the ammeter.

Just be careful how you do it.

 

[chknscratch]

Joseph,

There is a user from TN that did a very nice restoration on a B7100 and he added a voltmeter to the dash, I believe. I will post up if I can think of his handle. I think there have been 2-3 users on this forum who did a full restoration and he was one of them.

 

[JosephGozo]

hi

i have a spare volt meter in garage i was thinking of using it but thought an ammeter would be better.

i will try fit that one instead it should be working fine generally though.
I think a volt meter is easer to fit in the circuit? just take any live wire and ground the other end of the voltmeter?

thanks
joe

 

[JosephGozo]

hi again.
managed to install the volt gauge so far it reads around 13 when at idle.
but when almost at maximum spead with rotovator the needle creeps steadily between 15 and 16 Volts. is that acceptable or i should start looking at changing the rectifier?

if i switch on the working light at the back the volts drop to 14.5 and when i switch off the engine and leave key on the voltmeter reads close to 13.

i will do some readings on how to check the item before replacing but i am a bit worried i toast the battery or electrics.
joseph

 

[North Idaho Wolfman]

Sounds like you are right in the proper area of voltages that you should be seeing.

 

[kubotasam]

I have voltmeters on all 3 of my B7100's and the all run about 16 volts at wide open throttle. I to thought that was a little high when I first installed one on my tractors. However they have run fine for many years.

 

[JosephGozo]

hi thanks a lot i am still worried but i guess it is fine. i rarely do work at night but when i do baling i at times do some ocasional work late in the evening and it is good to know that the generator can keep up with both front and rear lights and baler electromagnets

joseph