23 replies to this topic

[gaspen]

Hello

 

As the car is still in the paintshop I put together a charge circuit on the bench using the wiring loom from the car. I bought a DVR3 unit, I believe I wired it correctly, I've checked it a dozen os times.  I follow Lucas service manual's instructions for tests but the dynamo does not charge.

 

C40's field resistance ~6.5 ohm, there is no short circuit in the armature and the  brushes are new.

 

I placed the C40 to a vise and turn it with a hand drill (its max rpm is ~3000 I guess)

 

With the multimeter connected to D and Earth I read 1.5 - 2 V

 

Same measure with D and F linked the voltage increases with rpm, highest reading is ~25 V. I can not measure at which rpm reaches 12V.

 

The dynamo works as a DC motor connected to the battery

 

I assume the C40 is in a good working order

 

Next I connected the battery, speedo with the IGN waning light, the IGN switch, as well as the DVR3 unit installed into the old RB106 box.

 

Switching on the IGN the light comes ON, it's okay.

 

Now I turn the dynamo with the drill the light remains ON at every rpm.

 

What could I do wrong ? Could be the DVR3 faulty ?

 

 

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[Spider]

From the Tests you've gone to some trouble to do here, the Dynamo does appear to be in working order and the issue I'd say is in the Regulator. The one you are using I'm not familiar with.

[gaspen]

From the Tests you've gone to some trouble to do here, the Dynamo does appear to be in working order and the issue I'd say is in the Regulator. The one you are using I'm not familiar with.

 

I think so too.

 

Meanwhile I learnt that maybe I should "bootstrapping" the dynamo - as it rested for some years - but I am not sure how should I do it.

 

DVR3 is an electronic voltage regulator, but it needs 3V to operate.

 

Should I connect everything and link D + F terminals and turn the dynamo to get that 3V ? 

[Spider]

 

From the Tests you've gone to some trouble to do here, the Dynamo does appear to be in working order and the issue I'd say is in the Regulator. The one you are using I'm not familiar with.

 

I think so too.

 

Meanwhile I learnt that maybe I should "bootstrapping" the dynamo - as it rested for some years - but I am not sure how should I do it.

 

DVR3 is an electronic voltage regulator, but it needs 3V to operate.

 

Should I connect everything and link D + F terminals and turn the dynamo to get that 3V ? 

 

 

'Bootstrapping' is done to re-polarise or change the polarity of the Dynamo, but as your Motors and also when run uncontrolled, has output, clearly it still has it's residual magnetism.

 

In writing this out, it did occur to me though that with your new Electronic Regulator, that would almost certain be made to suit either Positive or Negative Earth. If the Dynamo presently has the wrong polarity to suit the Regulator, there's every chance it won't work.

 

[weef]

The dynamo can easily be repolorised.

Decide what earth is required for your set and procede as follows.

Using a charged 12v battery, connect your earth lead to the body of the dynamo, with a wire from the battery "live" touch the field terminal of the dynamo one or two times, there will be sparks but do not worry.

The dynamo is now set up to charge with the battery circuit you have chosen.

It looks like the regulator needs a permanent battery supply, an earth, a dynamo output feed, a connection to the dymano field terminal and a charge warning light connection, but it should indicate what is required at the terminals.

When you have rigged up your test gear to check for an output the dynamo will be very difficult to rotate.

[gaspen]

 

 

From the Tests you've gone to some trouble to do here, the Dynamo does appear to be in working order and the issue I'd say is in the Regulator. The one you are using I'm not familiar with.

 

I think so too.

 

Meanwhile I learnt that maybe I should "bootstrapping" the dynamo - as it rested for some years - but I am not sure how should I do it.

 

DVR3 is an electronic voltage regulator, but it needs 3V to operate.

 

Should I connect everything and link D + F terminals and turn the dynamo to get that 3V ? 

 

 

'Bootstrapping' is done to re-polarise or change the polarity of the Dynamo, but as your Motors and also when run uncontrolled, has output, clearly it still has it's residual magnetism.

 

In writing this out, it did occur to me though that with your new Electronic Regulator, that would almost certain be made to suit either Positive or Negative Earth. If the Dynamo presently has the wrong polarity to suit the Regulator, there's every chance it won't work.

 

 

 

You can buy DVR3 units built for negative OR positive earth, they are not the same. Mine has negative earth.

 

dynamoregulator.com/products.html

 

I know how to re-polarise the dynamo and I've done it. Bootstrapping is a different procedure but I am not sure I undertand it correctly

 

DVR3 Datasheet

[floormanager]

Your wiring is the same as mine, -ve earth.  I've had a DVR3 for over 10 years now - I've even got a spare in case it packs up but it is still okay. As previously stated, there are different units for +ve and -ve cars and if you've used the incorrect one, then it's likely to be cooked. The type will be marked on it. 

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It will be worth talking to the supplier.  I know the original person who sold them, still sells the other units but he passed the ownership of the DVR3 to Dynamoregulators.

[gaspen]

Your wiring is the same as mine, -ve earth.  I've had a DVR3 for over 10 years now - I've even got a spare in case it packs up but it is still okay. As previously stated, there are different units for +ve and -ve cars and if you've used the incorrect one, then it's likely to be cooked. The type will be marked on it. 

DVR3.JPG

 

It will be worth talking to the supplier.  I know the original person who sold them, still sells the other units but he passed the ownership of the DVR3 to Dynamoregulators.

 

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[gaspen]

I've contacted the manufacturer. I have to install a resistor btween D and F :

 

This provides a path for the initial current to feed into the field winding and get the electromagnetic process started (positive feedback loop) once it get above 3 volts the regulator kicks in and then it takes over, the resistor will have no effect on regulation but burns about 0.6 amps of current which is not an issue on a 22 amp dynamo

[floormanager]

Why's that?  Is it because your on the bench??

[gazza82]

Why's that? Is it because your on the bench??

Think it's to do with Bootstrapping

[weef]

This is the usual procedure for a three bobbin voltage regulator to initiate charging.

First the ignition is turned on, and current flows from the battery, through the ignition switgh and warning light, through the armature windings, so lighting the warning light.

On startup the dynamo turns generating a small voltage due to its residual magnatism, this feeds through the current regulator and cut out coils to the dynamo field windings.

This I think is what you are referring to as "bootstrapping", because this current flow boosts the dynamo output causing a rapid increase in the dynamo voltage and the charging process begins controlled by the regulator.

It is maybe that the electronic regulator does not allow this feature so neccessitating the need for external resistors if the residual magnatism of the dynamo is low.

[floormanager]

Wow, every day is a school day for me at least!!

[gaspen]

Hi 

 

I still have issues with this setup. I've put everything in the car (engine, wiring loom, battery) and there is no charge

 

Now a 11 Ohm resistor is installed between D+F

 

1/ At idle the IGN light is on. While slowly increasing the rpm it fades a little but at more rpm it becomes ON again.

 

2/ Measuring the voltage at the battery it never shows more than battery voltage (~12,5V )

 

3/ Following the test in the old Lucas manual the armature ( between D and earth) produces ~1,6-1,7 Volts at 1500 rpm

 

4/ I also tested the field circuit at idle (see picture)  Ammeter between D and F, shows 2.4A, volt-meter between D and earth shows 17V

    While I am increasing the rpm the voltage also increases without limitation. It can reach 30V

 

What else can I check to ensure that the regulator is faulty or not ?

 

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[68+86auto]

If you can join the D and F wires near the regulator and the generator outputs voltage, as per test 4 then I'd say it is the regulator. The A and E connections should of course be tested first.

Throughout the following book, there are various generator and regulator testing procedures which I believe have a better explanation than the official Lucas instructions do. https://archive.org/...rical-servicing. I'm sure you will find the rest of it interesting too.

While I am increasing the rpm the voltage also increases without limitation. It can reach 30V

Note that the Lucas manuals say to carefully rev it in order to not exceed something like 16v.

Edited by 68+86auto, 06 May 2026 - 11:11 AM.