Charging system - Regulator polarizing question - PeachParts Mercedes-Benz Forum

mplafleur · #1 05-20-2006, 01:34 PM

Both of my SD's are now not charging. They both have had new regulators put in them, with no difference. One was a Hella, the other a Bosch. Now the Hella unit had an installation sheet that mentioned having to polarize the regualtor first, with no other instruction on how to do that.

I believ this involves shorting the B and D terminals on the regulator, but the regulator is internal so I don't think this can be done. I also heard this can be done by shorting the field to battery. With the internal regulator and the plug-in harness, I don't know where to access any of these.

Anybody know? Has anybody had to polarize a regulator before?

mplafleur · #2 05-20-2006, 11:47 PM

No one has any idea what I'm talking about???

mplafleur · #3 05-21-2006, 12:14 PM

No, nadda, out of luck???

1985 300SD Sady · #4 05-21-2006, 05:45 PM

You always have the toughest questions... your just way above the rest.

I dont know what to tell you, I just got a new regulator, popped it in plugged it all in and it works.

It is weird that both are now not charging... did they go out at the same time and you changed out regulators at the same time?

EDIT: After some research, I found that for these 6v tractors with generators on them, they need to polarize their regulators... and that "This problem does not exist with an alternator, but only generators."

Quoted from http://www.antique-tractor.com/pipermail/farmall/2004-June/000089.html

kitchenrat · #5 05-21-2006, 07:22 PM

it is necessary to polarize a regulator on a generator system. do not polarize a regulator on an alternator system or you will damage the regulator.

mplafleur · #6 05-21-2006, 10:26 PM

Quote:

Originally Posted by 1985 300SD Sady

It is weird that both are now not charging... did they go out at the same time and you changed out regulators at the same time?

Different times.

Quote:

Originally Posted by 1985 300SD Sady

EDIT: After some research, I found that for these 6v tractors with generators on them, they need to polarize their regulators... and that "This problem does not exist with an alternator, but only generators."

Quoted from http://www.antique-tractor.com/pipermail/farmall/2004-June/000089.html

That's what I thought. But the sheet that came with the regulator (which is made specifically for an ALTERNATOR) says that you may need to polarize it.

I have a charging system analyzer.

The tester will show:
Over charge (Regulator shorted)
Not Charging (Field Regulator Open)
Alternator (Rectifier/Stator)
Low Battery (Low Charge/Bad Cell)

The tester says that I have a regulator problem, not an alternator problem. The unit is supposed to sense the filtered and unfiltered output of the alternator so if the thing is working, the alternator is supposedly ok.

mplafleur · #7 07-02-2006, 03:07 PM

Replaced the alternator today. Now it is charging at 13.9v steady at idle and under load and at fast idle.

I bought a really nice (new looking) reman Bosch unit on eBay for $60. No core required. It was a 65 amp unit which is way more than required for my SD. Only drawback is that it is a single pully, not a double.

Life is good.

leathermang · #8 07-02-2006, 03:46 PM

So your charging system analyzer said it was regulator but replacing the alternator fixed the problem... ?
That is a bummer when you can't trust diagnostic tools like that... particularly with something invisible like electricity....

mplafleur · #9 07-02-2006, 03:58 PM

What the tester actually says "Field/Regulator Open".

With an internal regulator and the field I guess, being routed through the connector on the alternator, the problem still could be in the alternator.

Matt L · #10 07-03-2006, 11:30 AM

It isn't the regulator that needs polarizing on a generator system, but the generator itself.

However, you do it by shorting two regulator terminals after installing a new generator (not necessary for units that have been run on the same polarity of vehicle) but before starting the engine.

The generator needs to be polarized because it starts generating before the regulator contacts close. The contacts close when there is demand for current, and the generator is producing voltage. If by chance (50%), the generator is polarized the wrong way, it will produce voltage but opposing that of the battery, and will be a 24V direct discharge of the battery (12V battery + 12V generator) when the regulator contacts close (just after starting the engine).

Alternators have diodes to rectify the current, so cannot actively discharge the battery. Thus this procedure is not necessary for an alternator.

mplafleur · #11 07-05-2006, 09:05 AM

Yup, It makes sense now...

Thanks!