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Sun Jan 11, 2009 10:53 pm

Ok, i have heard several times about Polarizing the Gen, but what it the correct way to do it, and Why. What if you just installed a new one would it work or Not?
Thank's

Sun Jan 11, 2009 11:18 pm

From vw-resource.com:

Questions are often asked regarding the need to polarize a generator. If the generator is charging (the battery stays charged) then you don't have to polarize it. When a generator has been left unused for a long time (months or years), the metal core looses it's magnetism, and it NEEDS a little residual magnetism to start the charging process. Polarizing just gives it enough "boost" in magnetism to start it charging properly. When it's being used, it keeps its core polarized core so no need to do it again.

Note: Why do generators need to be "polarized"? Automobile generators need some magnetism to get started. This "residual" magnetism remains in the field pole pieces even after the engine has stopped. The next time the generator starts up, the residual magnetism creates a small voltage in the armature windings. Not enough to charge the battery, but enough to allow the field windings to draw current. As the field current increases, the pole pieces create even more magnetism. That makes even more voltage in the armature, and the cycle continues until the generator is capable of producing maximum output.

What happens though to a generator which has been stored a long time or is freshly rebuilt? The residual magnetism may have decreased to the point where it can no longer get the generator started producing voltage. In the case of a new generator or one which has been mis-treated, the residual may even be of the wrong direction (North and South poles reversed). Polarization is a simple process used to restore the field pole residual magnetism and ensure the magnetic direction is correct.

To polarize a generator, connect a jumper wire from the (DF) terminal on the generator to the generator frame. Remove the fan belt, then connect a wire from the positive terminal on the battery to the (D+) terminal on the generator. The generator shaft should start to spin.

Note: Don't run the generator this way for more than a few seconds to avoid overheating.

The generator will now be properly polarized. If the generator did not spin during this process, the generator is most likely defective.

Put the fan belt back on and re-test the generator voltage with the (DF) terminal grounded. If the output voltage is still low, the generator is defective.

Note: Voltage regulators do not need to be polarized -- they are not polarity sensitive. Even if voltage regulator came with instructions to polarize it -- these instructions actually polarize the generator, not the regulator. The regulator manufacturer simply wants to make sure that your generator will work properly so you don't blame the voltage regulator.

Neither to alternators need to be polarized. Alternators use a trigger current to start the process of charging - electromagnetism, so don't need any internal magnetism to begin with, like a generator does.

That trigger current is supplied via the alternator dash light (it's a tiny current and won't make the light glow when the engine is running) so if that bulb blows - the battery won't get charged and it will go flat. Curious circuitry VW used, but it works just fine. So that means that with an alternator equipped VW, you should always glance at the dash as you turn the key and make sure the Alt light does glow with just the key on, just to make sure that that circuit is intact.

I had to do that to MY old '72 Super as the battery was not charging, after i did this i could tell it WAS charging cause the lights would get brighter somewhat after i gave it a lil gas. Good luck!

Mon Jan 12, 2009 2:52 am

Speedy jim's site has pics>

http://www.nls.net/mp/volks/htm/gen.htm

jim

Mon Jan 12, 2009 7:04 am

Yes, you can polarize the generator if it's already installed in the VW. Take off the belt and all the wires. Then it's just like it was sitting on a bench. Wire it up correctly to spin it as an electric motor for a few seconds (only).

Wed May 15, 2013 3:05 pm

is it possible for a generator to lose its magnetism after an electrical short? My son took some friends for a ride in my '66 and now the generator light is on. The small rubber mat that I had placed over the battery below the seat had slid off and I think the seat springs may have made contact with the battery and caused a short. The brushes and commutator on the generator still look ok.

Wed May 15, 2013 4:16 pm

I recently installed a replacement regulator and did nothing to polarize the generator through it- didnt know.
How do you polarize the generator through the regulator? Would it be OK to do this rather than polarizing at the generator itself?

Wed May 15, 2013 4:38 pm

Polarize the generator like Cusser mentions above.

You do not need to polarize the regulator, also mentioned above.

Wed May 15, 2013 5:06 pm

VeeDubDoug wrote: Polarize the generator like Cusser mentions above.

You do not need to polarize the regulator, also mentioned above.

Umm- I KNOW i dont need to polarize the regulator. i was asking about the procedure to polarize the generator THROUGH the regulator, as opposed to doing it right at the generator.

Sun Feb 07, 2016 10:32 am

If I have positive ground do I connect the jumper cable to the negative pole of the battery?

Sun Feb 07, 2016 10:37 am

Scorcho wrote: If I have positive ground do I connect the jumper cable to the negative pole of the battery?

Why, oh why, would your VW be "positive ground" ?

I wouldn't go ANYTHING until that situation is verified !!!

My brother had an MG once that was positive ground.

Mon May 30, 2016 6:59 am

I have a 1971 BSA Lightning that's positive ground...oh those Brits.
Foot brake and shift reversed too.

Tue Oct 24, 2017 9:21 am

I can polarize my sons generator but it is still not showing any power. It will spin nicely when I get the power to it, so that seems like it should work. I put a test light on the positive side and get nothing.

Tue Oct 24, 2017 11:16 am

salicoskungfu wrote: I can polarize my sons generator but it is still not showing any power. It will spin nicely when I get the power to it, so that seems like it should work. I put a test light on the positive side and get nothing.

Yeah, that should work. With the wires to the generator disconnected, exactly how are you testing this? Test light should go to D+ and to negative ground, then for a second or two jump Df to ground and should light.

If you don't have a digital multimeter, maybe time to get one; free or $6 at Harbor Freight, you'd use that the same in 0-20 VDC mode. Either start the engine or take off belt and spin with impact wrench to test the generator.

Tue Oct 24, 2017 3:20 pm

Here is an updated link to Speedy Jim's page on testing the generator.
http://speedyjim.net/htm/gen.htm
Follow the instructions and report back your finding.

When you ground the DF terminal with a voltmeter/multi meter on the D+ terminal report back the voltage produced as you rev the engine to 2100rpm and get the generator charging. With the DF grounded it should output the max voltage (35v+).

BTW, when you polarized the generator, which direction was the pulley spinning? Someone correct me by I believe it should spin CW.

Tue Oct 24, 2017 6:10 pm

ashman40 wrote: BTW, when you polarized the generator, which direction was the pulley spinning? Someone correct me by I believe it should spin CW.

Yes, should spin clockwise as you look at it from the rear of the VW.

Sat Aug 22, 2020 12:15 pm

Cusser wrote: ashman40 wrote: BTW, when you polarized the generator, which direction was the pulley spinning? Someone correct me by I believe it should spin CW.

Yes, should spin clockwise as you look at it from the rear of the VW.

I’m trying to polarize my 6 volt new generator right now but it spins Counterclockwise ,, why is it doing that ?? I can get it to spin the other way by hand by adding power to it .. an I doing something wrong ??

Sat Aug 22, 2020 2:17 pm

broozebrothers wrote: Cusser wrote: Yes, should spin clockwise as you look at it from the rear of the VW.

I’m trying to polarize my 6 volt new generator right now but it spins Counterclockwise ,, why is it doing that ?? I can get it to spin the other way by hand by adding power to it .. an I doing something wrong ??
I have heard you can reverse polarize your generator. This happens when you accidentally connect the wires backwards at the generator posts. Follow Speedy Jim's diagram:

Disconnect all the wires from the generator. Run a ground wire between the DF and a good ground point (distributor body).
Use a long wire or your battery jumper cables to get power from the battery (+) post. Touch the D+ terminal. The pulley should start spinning CW on its own. If it starts spinning CCW, try forcing it to spin CW. Once it is spinning in the CW direction, disconnect the D+ wire and after the pulley comes to a stop, touch the battery (+) wire to the D+ again. It should now spin CW. This indicates you have properly re-polarized the generator (field coil).
You should also check the brushes while you are at it. Bad brush contact could possible cause the generator to spin in reverse or not spin.

Sat Aug 22, 2020 2:43 pm

Thank you Ashman ,, I’ll try it out and see what it does ..

Tue Oct 06, 2020 5:55 pm

Reviving this thread. Car is running, but battery not charging. I put a multimeter on the generator and it is reading around 1.6V. I am in a weird place because it is putting out some voltage, but very low. My generator warning light stays lit. The car did sit for about 7 years without running. Would polarizing the generator help the low output? Would taking the belt off vs running the car polarize it any differently? Sorry for what are probably dumb questions.

Tue Oct 06, 2020 7:40 pm

Another easier way to polarize it is to with the key turned off jumper B+ to D+ with some fair sized copper wire battery cables work. Takes just a second or two you will hear it kick a little and see it if you look at the fully installed belt and pulley it's the same procedure as above only it depends on the voltage regulator to be grounding DF and it's done with the belt on.