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Generator or voltage regulator?
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BK911
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PostPosted: Fri Jan 15, 2016 9:38 am    Post subject: Generator or voltage regulator? Reply with quote

Hey guys,

12V '64C
Gen warning light started coming on.
It would clear around 3k rpm, but not anymore.
Measured battery voltage with and without engine running at 12.5V.
How can I tell if its the regulator or generator?

Thanks!
BK
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tallman206
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PostPosted: Fri Jan 15, 2016 11:49 am    Post subject: Re: Generator or voltage regulator? Reply with quote

USUALLY, if the generator light comes on, the problem is in the Generator, and most likely the brushes are worn out or don't have sufficient spring tension for proper contact. Getting the lower brush out is a bear. The dash red light is directly tied to the generator D+ output, and is therefore a good indication that the generator has no output.
I say USUALLY, because I recently had a friend's 356 stump me. His voltage regulator failed with the CutOff contacts open, and running for a 1000 miles or so, the generator had no load, and the commutator lost contact on the brushes. But I consider that a rare occurrance.
Jerry
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Jerry Henning
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tallman206
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PostPosted: Fri Jan 15, 2016 11:56 am    Post subject: Re: Generator or voltage regulator? Reply with quote

Remove brush cover, and check top and bottom brush length. Brushes should be above the edges of their holders. Try running the engine while pushing inward on both brushes to see if your light goes off.
I find the best way to get out the bottom brush is to loosen the generator clamp, remove the four bolts holding the generator backing plate to the fan shroud, and rotating the generator on its cradle till you can get to the bottom brush. Use only Genuine Bosch replacement brushes for best results.
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BK911
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PostPosted: Fri Jan 15, 2016 3:39 pm    Post subject: Re: Generator or voltage regulator? Reply with quote

Thanks jerry!
Heading out to garage now. Smile
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tallman206
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PostPosted: Fri Jan 15, 2016 4:45 pm    Post subject: Re: Generator or voltage regulator? Reply with quote

Good ole Rocky Top
Rocky Top Tennessee!
(Says an ex Memphis River Rat)
Try to hook up with the loosely organized Thunder Roads 356 social group out of Knoxville. Jim Johnston is a ringleader. Great folks. There is also the Tennessee Tubs out of Nashville. Contact info here: www.porsche356registry.org/clubs

Back to generators - you don't say what 12V voltage regulator you have.
Nevertheless, your symptoms of revving the engine point to a classic condition of an intermittent generator output, typically caused by brush failure.
Anyway, you can test the generator by itself.
Disconnect the DF (field control for the Dynamo), and the D+ (dynamo output) leads from the generator (dynamo). Use a fairly large wire to connect the DF lead to ground (earth or chassis ground). This will cause the generator to operate at full output (no regulator control). Then use a voltmeter from D+ to ground to measure the generator output, and start the engine. If the generator is putting out, you should probably measure 18-20 volts out when you rev the engine. This is not a definitive test, because as you have noticed, sometimes the generator light goes out, and sometimes it is on. You might catch it during the test when the generator decides it wants to work for a bit.
More for you to consider.
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Jon Schmid
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PostPosted: Sat Jan 16, 2016 3:49 pm    Post subject: Re: Generator or voltage regulator? Reply with quote

I had this symptom on each of my cars. Once was the generator, once was the regulator. I would check the generator output first.
P.S. Jerry, Roll Tide!!! Cool
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BK911
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PostPosted: Sun Jan 17, 2016 10:13 am    Post subject: Re: Generator or voltage regulator? Reply with quote

Finally had a chance to mess with the 64 a bit.
Zero volts on D+ at any rpm.
Wrapped a stick with some 600 grit sand paper and pressed against the commutator with engine running.
Now I get ~2V at idle and >13V above 2.5K rpm.
Am I done?
Smile
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tallman206
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PostPosted: Sun Jan 17, 2016 1:59 pm    Post subject: Re: Generator or voltage regulator? Reply with quote

Perhaps, or perhaps not.
How are the lengths of the top and bottom brushes (higher than their holders?), and how tight do the springs feel?
Certainly you can clean up the commutator as you have done (don't use emery paper, it is electrically conductive and leaves conductive residue) blow out the abrasives and dust with compressed air, reconnect the regulator, and you will probably be ok for a while. But if the brushes fail again, you should replace them.
Also, while you are looking, check the copper commutator segments. There should be a recessed gap between the copper segments (its called undercutting). If the copper segments wear down to where there is no more undercutting, the brushes, old or new) will never seat properly, and the generator armature must be disassembled and reconditioned.

At least you identified the problem area - the brushes had lost contact with the commutator. Now you need to see if they will work reliably, or will need replacing.
Jerry
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BK911
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PostPosted: Sun Jan 17, 2016 4:28 pm    Post subject: Re: Generator or voltage regulator? Reply with quote

Thanks for all the help jerry!
Pulled the generator out just to inspect better.
The bottom was covered with oil residue.
Pulled the brushes and cleaned up everything pretty well.
Now the gen light goes out just before 2k rpms.

The brushes stick out about 1/8" above their holders.
The commutator has the grooves, but they are kinda shallow.
But they are there!

I recently fixed an oil leak at the bottom of the oil filter housing.
I also connected the oil fill thingy to the carb.

Hopefully those two issues were the reason for the oily film.

We will see!!

Time to put some miles on the car again.
Porsche show coming up!!
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PostPosted: Sun Jan 17, 2016 7:40 pm    Post subject: Re: Generator or voltage regulator? Reply with quote

BK911 wrote:
T
Now the gen light goes out just before 2k rpms.


I'm no expert, but based on the experience of my 356's that RPM level is still way too high to be needed to get the light to go out. It should be out at high idle (800-900 RPM). I would clean the regulator contacts and check ALL of your connections from the battery aft. If the light is still on I would have the regulator looked at. Like I said earlier, it happened to me. Good luck--
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PostPosted: Mon Jan 18, 2016 7:46 am    Post subject: Re: Generator or voltage regulator? Reply with quote

It has been my (limited) experience that the Bosch small frame 12 volt generators (as come on early 912s) have a difficult if not impossible time producing output at idle. Mine does not start producing (red light out) until about 1100-1200 RPM. So yes, 2000 rpm does sound a bit high, but I wouldnt expect the red light to be out at idle like a typical 6V generator.
First, lets drive it a bit to see what you have got.
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PostPosted: Mon Jan 18, 2016 3:20 pm    Post subject: Re: Generator or voltage regulator? Reply with quote

I agree with you Jon.
Its not as good as I would like, but hopefully good enough to keep a charge.
I will go through and clean off all the connectors and hope it improves.
I will also put some miles on her!!
Thanks for all the help guys!!!
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PostPosted: Mon Jan 18, 2016 6:12 pm    Post subject: Re: Generator or voltage regulator? Reply with quote

Please consider giving us an update on the situation after you have put some miles on it. Thanks.
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PostPosted: Mon Jan 18, 2016 6:54 pm    Post subject: Re: Generator or voltage regulator? Reply with quote

BK911 wrote:
I agree with you Jon.
Its not as good as I would like, but hopefully good enough to keep a charge.
I will go through and clean off all the connectors and hope it improves.
I will also put some miles on her!!
Thanks for all the help guys!!!


Hey, once again a bad experience I had which I have posted in the past but basically my car came to a dead stop in a not so convenient place. Turned out to be a loose negative battery cable. Check everything electrical on these cars--they're old and all kinds of weird shit can and probably will happen. Good luck.
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PostPosted: Thu Jan 28, 2016 11:12 am    Post subject: Re: Generator or voltage regulator? Reply with quote

Snow finally melted, and enough rain to wash the salt away.
So took the car to work.
35 miles to work with lights on and gen warning light on.
Not a fun drive!
But made it home, so all was ok.
Retesting the generator, and only getting ~10V at >2k rpms.
Cleaned it up again without much improvement.

My next step it so clean all connections and retest.
Also retest as Tallman suggests with bypassing the regulator.

But, if I need to buy parts, or a rebullt one...

The bosch generator part number is LJ/GEG 200/6/2600
It used to put out 12V.
I guess the "6" doesnt mean 6V??
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PostPosted: Thu Jan 28, 2016 1:56 pm    Post subject: Re: Generator or voltage regulator? Reply with quote

You have a 6 volt generator. It is possible that someone in the past may have converted it to 12v with replacement of the armature and changing the field coils to 12v. If they did it right, the frame would have been stamped somewhere with "12V" to let you know. If it is really a 6V generator, you are asking a lot of it to produce 12V. I would consider changing it to a true 12v generator, as used on the early 912s (small diameter 90mm?). The later 912s used a larger diameter generator (105mm?), and to use it, you would have to change generator stand, oil filler, backing plate.
If the armature looks good - no unsoldered segments or solder splatter, I still think new brushes might possibly help, if it was working before. Test the generator by itself as described before, by disconnecting DF and D+, then grounding DF to activate full output, and measure at D+ output. A 6v generator at full output can produce more than 14v at speed to produce charging, but is not the best idea.
Let us know the outcome.
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BK911
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PostPosted: Thu Jan 28, 2016 4:55 pm    Post subject: Re: Generator or voltage regulator? Reply with quote

Thanks again jerry!!
Tried to do the test but battery is dead.
Put on trickle charger and cleaned all connections.
The Df connector was pretty bad so redid that.
Made up the ground wire to ground Df tomorrow when battery is charged.

Checked gen for a 12V stamping and couldn't find one.
Battery is 12V.
Before I would get ~13.5V from gen so that's why I thought it was a 12V.
So confusing!
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PostPosted: Fri Jan 29, 2016 2:58 pm    Post subject: Re: Generator or voltage regulator? Reply with quote

With Df grounded
Measuring at D+
5V at idle.
12V at 1500 rpm


So voltage regulator issue?
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PostPosted: Fri Jan 29, 2016 4:01 pm    Post subject: Re: Generator or voltage regulator? Reply with quote

Again, far from being an expert but what's the harm in checking the regulator? 5V at idle is low on a 6V car, and yours is a 12V? That doesn't sound right to me.
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PostPosted: Fri Jan 29, 2016 5:13 pm    Post subject: Re: Generator or voltage regulator? Reply with quote

Hey jon,
I would love to check the regulator.
Any pointers on how to?
The only electrical connection that I can think of that I didn't clean is the engine/tranny ground strap.
Haven't been able to find it yet.
Will put car on ramps tomorrow and dig around underneath.
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