Adjusting the D-Regulator

[AndrewCologne]

Hi,

the last weeks I went very into the details of checking and adjusting the D regulator for my split bug.

Adjusting can be done very easily, you just have to loosen a bit the screw on the left side.

Then you can slightly move the left part of the voltage regulating unit up and down which enlarges or reduces the gap between the regulators spool/core and the regulation unit … and exactly this is what affects the voltage output.
In my particular case the perfect output was achieved by a gap of 0,9-0,95 mm by using a feeler gauge. Be careful, as just a change of 0,05 mm already will affect the voltage significantly.

Attention … before working on the parts of the regulator ALWAYS, yes ALWAYS disconnect terminal 51 from the regulator to the battery and insulate the end of the wire to avoid a short circuit when working on the parts of the regulation units!

Here’s the workflow:

1. Disconnect terminal 51 from the regulator to the battery and insulate it properly so it won’t get in contact with ground
2. Connect a voltage multimeter to terminal 51 (red) of the regulator and a part of the engine which gives a proper ground (black) connection.
3. With a all power consumpting units switched off start the engine an and check the multimeters display. The specs say that it should read at higher idle 6,5-7 Volts and at 2000-3000 rpm about 8,1 Volts at 20°C environment temperature. On cable brake models, be sure handbrake is released so the breaking light is off!
4. If the output at higher revs results in a lower voltage than slightly enlarge the gap between the regulators core/spool and the upper bar of the left voltage regulation unit. If the voltage is too high, then slightly decrease the gap. Related to the magnetism of the spool at a given voltage this will make the points of little metal stripe get in touch with the left contact faster or slower which affects the voltage limit/output.
5. Adjust the gap until a voltage output of about 8,1 volts at 2000-3000 revs/rpm is achieved. But do this only when the engine is not running, so no current will reach the regulator while adjusting! So switch the engine off, adjust, re start the engine, check again, and so on ... till the proper voltage is achieved.
6. Tighten the left screw, start the engine and re check the voltage output across all revs.
7. Switch engine off and reconnect the wire to terminal 51 of the regulator but leave the multimeter connected … start the engine and check again the voltage across all revs. You will recognize that the voltage now is significantly lower across all engine revs due to the connected battery which acts like a voltage buffer.
8. Disconnect the multimeter from the regulator and connect it directly to the battery under the backseat and leave the multimeter on the right passenger seat where you can see the display when driving.
9. Now do a test drive with your car with all additional electric consumpting units switched off (headlights, tail lights, breaking lights … all off) and watch the multimeters display across all revs/rpm’s. After a few hundred meters driving the voltage should be bout 7-7,2 volts at higher revs which means no boiling of the battery will occur and that the battery will be properly charged.

If at higher revs the voltage output of the regulator with terminal 51 disconnected to the battery gives proper 8,1 volts but later at a test drive with the battery/terminal 51 connected the voltage results at higher revs significantly higher than 7,2 volts or won’t rise over 6,8 volts, then you should check your battery’s state.
Keep in mind: always do adjust the gap using the setup with the battery „not“ connected to terminal 51 of the regulator. By doing the adjustment respecting this you can be sure that a final proper voltage of about 8,1 volts will reach the battery. Adjusting the gap with the battery connected at terminal 51 to simply achieve the 7,2 volts at high revs is not the proper way.


Here you can see the test across all revs and the achieved output of the proper 8,1 volts at higher revs ... with disconnected terminal 51 on the regulator.

https://vimeo.com/216904567


Cheers from Cologne
A.
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1950 Split Window Grey
1955 Oval Window Stratosilber
1982 Porsche 911 3.0 SC Black

[mkbug]

Very nice instructions - thank you.
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I'm Martin


My Build: https://www.thesamba.com/vw/forum/viewtopic.php?t=667183

[pastellgreen]

Superb, thank you very very much!

That would be something for the FAQ section? I would apreciate beeing able to find this description quick and without searching long when needed...

[EverettB]

First, thanks for posting this technical breakdown.

[gatorwyatt]

This a super helpful post. These instructions are very easy and worked perfect. What I found was the measurement for the adjustment was much larger than the .9mm and just wanted to mention it. It was where I started and found the generator only putting out 6.5v with term 51 off.

Now we need one just like this for the round regulator!
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