TheSamba.com :: View topic - Do I need to "polarize" my new generator?

Thu Feb 28, 2008 5:09 pm

Sorry,I have a newbe question.I bought a new generator and regulator for my '65 bus(12 volt)I'm trying to get it on the road.The paperwork that came with it said I have to "polarize" the generator by momentarilly touching the D+ wire to the B+ wire?Did I read it right,or miss something?please explain.

thanks

Thu Feb 28, 2008 5:13 pm

yes you need to polorize your generator.

run a jumper wire from DF to ground, and one from D+ to the battery positive lead.

you only need to let it spin for a few seconds.

Thu Feb 28, 2008 5:24 pm

I have all the wires connected as it needs to be,to run.... next connect battery terminals,and I use some extra wire to perform this task?Sorry I have never done it,and do not want to fry something.Hate to sound stupid.

Thu Feb 28, 2008 5:37 pm

remove the generator belt. remove the wires that run to the regulator, df and d+
connect the df jumper to ground, and d+ to the battery positive, the generator will start to turn.
let it spin for a few seconds and reconnect the regulator wires to generator and install the belt. fire her up, your done.

Thu Feb 28, 2008 5:42 pm

thanks man!

Sat Aug 15, 2009 8:19 am

Does anyone know if you can use the 38 amp regulator instead of the 30 amp regulator with a 30 amp generator?

Sat Aug 15, 2009 8:45 am

I would NOT do that, as you might fry one of the items. You should be using components of matched amps (both 30 or both 38 amps).

Bill

Mon Aug 17, 2009 7:20 am

Thanks. The 30 amp mechanical regulators seem to have dried up. Most sales are of the electronic ones. Are there any "electric" people out there that could elaborate on physically how the 38 amp regulator might misread the 30 amp generator?

Mon Aug 17, 2009 10:27 am

http://vintagebus.com/wiring/polarize.jpg

Found this on Vintagebus.com It's a different method than what has been described here, but worth a try.

Mon Aug 17, 2009 10:36 am

There is no reason a 38 amp regulator won't work with a 30 amp generator. The regulator reads volts and amps off the battery and charges accordingly.

To you electrical engineers out there, I know this is not technically correct. Please feel free to post a couple of pages proving the same thing.

Mon Aug 17, 2009 4:13 pm

Rusty O'Toole wrote: Please feel free to post a couple of pages proving the same thing.

Ha, totally.

I decided to put my mouth where my money was so I took the 30 amp gen and the 38 amp reg to Broadway Auto Electric in Lemon Grove, California. The owner told me, "Sure it will work as the regulator is a voltage regulator which will keep the generator's voltage higher than the battery to fill it." "The amperage will depend on how much is being replace or drawn off which should never approach 30 amps.""However, if for some reason I neglect the battery's charge or it starts to get old, the limiting factor of the 38 amp may allow the generator to exceed it's output rating and possibly fry.".

So, I'll be the guinea pig and the canary in the coal mine.

Mon Aug 03, 2015 9:02 pm

Speaking of "polarizing", I have a question...

The above answers were about a more recent 60's generator. I have a "thin-slot" Bosch LJ/REF/160/6/2500 L21 six volt factory "exchange" generator that hasn't been used since it was rebuilt by the VW factory for the exchange motor program back in the early 60's. It obviously needs to be polarized before use (very soon!).

My 1959 Factory workshop Service manual basically says the following about the "polarizing" process:

About the wires coming out of the generator case, "The thicker cable from the generator comes from the positive brush and must be connected to the "D+" terminal of the voltage regulator. The thinner cable comes from the field coils and must be connected to the terminal "DF" at the bottom of the voltage regulator".

I understand that you disconnect the voltage regulator from the wires coming out of the generator. So you have the generator either strapped down on the generator stand with the regulator completely disconnected from the generator wires, or you can do this with just the generator itself on a workbench. You'll need a few jumper wires and of course an appropriate 6 or 12 volt automotive battery for the generator you have.

The manual goes on to say about the "polarizing" process: "Cable "DF" of the generator needs to be connected to ground (D-), the positive battery terminal connected to terminal (D+), and the negative battery terminal connected to ground (D-)".

Ignore the circled A for ammeter (illustration for testing the generator, but similar for the polarizing process)...

"D-" can be the ground screw on the generator case or a ground on the crankcase. The generator needs to hooked up and spun as a motor for just a second or two to "polarize" it.

Okay, my question is related to the fact that I have one wire (the thinner one from the field coils) coming out of one hole in my "L21" generator case, and TWO wires coming out of the other hole (one thicker wire from the positive brush and one unknown thin wire) and both of those are attached together to terminal #61 below the voltage regulator.

one thinner wire on the left... and two (one thick and one thin) wires on the right...

close up of the two on the right...

in this shot you can see the ground screw, and the end of the Bosch generator part number "L21" on the generator case...

I guess my question is: When "polarizing", do I treat the two wires as one and keep them connected together for the polarizing hook ups? I really don't want to damage this virtually new factory rebuilt generator. while "polarizing" or when we fire up this engine!

HELP! Thanks for any advice from our electrical geniuses out there! And can anyone else out there with an "L21" six volt generator confirm that you also have two wires coming out of the generator to the voltage regulators #61 terminal as in my photos? Thanks gang!

Bill Bowman

Tue Aug 04, 2015 9:39 am

BulliBill wrote: When "polarizing", do I treat the two wires as one and keep them connected together for the polarizing hook ups?

Yes. It is just a more modern way of connecting the brush. The old way it was down inside hidden.

Tue Aug 04, 2015 9:47 am

Thanks Barry! Man, I owe you a lot of beer! The two wires on that one side kinda threw me, although electrically, that is not hard to do! I really don't want to mess up this nice old generator, so I'd rather ask dumb questions than screw things up!

When running it as a 6 volt motor during the polarizing process, should it spin fast or slow (as I've seen some mention). Should anything be read into the "speed" of the momentary spinning?

Thanks!

Bill

Tue Aug 04, 2015 10:00 am

Hook it up with no belt and go 3 seconds. You can do it with the belt on but only go 1 seconds.

Thu Aug 06, 2015 8:37 pm

Keep in mind what you're trying to do here: the point of "polarizing" is to run current through the generator field winding so that it is magnetized in the proper polarity. It will retain residual magnetism from this process. Residual magnetism is what gives a generator its "self-starting" property (e.g. what makes it initially generate voltage of the proper polarity when you spin it).

So, seeing as that the generator field winding is connected between the 'D+' terminal and the 'Df' terminal, all you need to do is (1) disconnect the generator wiring, then (2) connect a 12 volt battery between 'D+' (positive) and 'DF' (negative) for a couple of seconds. That's all it takes.

If you also connect the battery negative to the generator case, the generator armature will be powered and the generator will spin like a motor, but this isn't necessary for successful polarization.

Fri Aug 07, 2015 12:58 am

BarryL wrote: Rusty O'Toole wrote: Please feel free to post a couple of pages proving the same thing.

Ha, totally.

I decided to put my mouth where my money was so I took the 30 amp gen and the 38 amp reg to Broadway Auto Electric in Lemon Grove, California. The owner told me, "Sure it will work as the regulator is a voltage regulator which will keep the generator's voltage higher than the battery to fill it." "The amperage will depend on how much is being replace or drawn off which should never approach 30 amps.""However, if for some reason I neglect the battery's charge or it starts to get old, the limiting factor of the 38 amp may allow the generator to exceed it's output rating and possibly fry.".

Spot on. If you use a 30 amp regulator with a 38 amp generator, it will work fine but you then only have a max 30 amps to power the vehicle - the regulator will not allow more than 30 amps through to the battery.

If you try to use a 38 amp regulator on a 30 amp generator, most times - with a good battery holding a good charge, you will get away with it because you will not need big amps to charge it. But if your battery is in bad need of a charge (tired, left unused for some time, a couple of hard starts), the regulator will try to let 38 amps through from the 30 amp generator and so the generator will start to heat up and can eventually cook/fail.

Mon Feb 08, 2016 9:35 am

I got a new regulator for my 6V bus with positive ground. Does the fact it has postive ground instead of negative ground change where i should connect the jumper lead to in the battery? like should i actually connect the positive battery terminal to D- and the negative battery terminal to D+?

Should i even polarize the generator if I am just replacing the regulator?

Mon Feb 08, 2016 9:56 am

VW electrical systems are negative ground.

Mon Feb 08, 2016 10:31 am

You normally do not need to "polarize" the generator if you're just changing the regulator. All polarization does is establish a residual magnetic field in the generator field steel, which is used to "start" the generator when the engine spins it.