Car not charging, dynamo or control box?

[culp]

I have a newly restored 1970 Traveller that is not charging, the ignition light is on all the time.

The dynamo is fairly new, from Lucas, but hasnt been used for 3.5 years. Connections on the back are one brown and yellow wire and one brown and green wire.

I have 12.5 volts across the battery when the engine is running.

The control box is the orginal from the car, prior to the restoration the control box was bypassed as the car had an alternator. Again unused for 3.5 years

I have a wire coming from the loom that is green and brown and seems to be redundant. I thought oil filter warning light.

I understood the control boxes are pretty bullet proof, but I'm thinking this is at fault here?

Can i test the dynamo in the car with a voltmeter?

Any advice gratefully received

[svenedin]

I would first make sure that the dynamo is connected properly to the voltage regulator. The D (output) connection from the dynamo connects to the D terminal of the voltage regulator. Likewise F (field coils) from the dynamo connects to terminal F. Remove the D and F connections from the dynamo and at the control box end and check for continuity with a multimeter. If this tests correctly and the dynamo still does not charge (after replacing the connections of course) then try cleaning the contacts on the bobbins inside the control box. Also check the E (earth) connection of the voltage regulator for continuity to whichever is the earth side of the battery in your car. If that still does not work you can look up how to measure the output of the dynamo (which yes can be done with the dynamo in the car). See: https://www.howacarworks.com/electrical ... ing-output

The voltage regulator is not bombproof by any means. It has points that corrode and erode (pit) just like points in the distributor and the fuel pump. The contacts may be dirty from the car standing for years or they may be dirty and also worn out. The voltage regulators currently available are poorly made, unreliable copies of the original and imho not worth having.

If your dynamo is pretty new chances are it is not at fault BUT another thing to do would be to check that it has been polarised to the correct polarity for your car. If in doubt polarise it.

Stephen

[myoldjalopy]

Well, if you've got a voltmeter, you might as well use it to do the suggested tests. However, a rough and ready test for the dynamo is to see if it will run as a motor. You can do this in the car. Simply slacken off the dynamo bolts so you can remove the fan belt, then open up the control box and press down on the right hand bobbin, as you face the car, to close the contact points. Do not touch the bobbin on the left. If the dynamo is any good, it will spin briskly and smoothly. Make sure the contact points come part again after this test, they should do. If the dynamo does run briskly as a motor, and all connections at the dynamo are good, I'd suspect the control box.

[culp]

Which one is the field terminal? the smaller spade terminal or the big one?

[svenedin]

Smaller one is field

[culp]

sorry stupid question I figured out which terminal is which

[svenedin]

Just under bonnet of my car. Oil pressure sensor wire is green and brown as OP queries.

Stephen

[culp]

The plot thickens!

I took off the fanbelt and then closed the right hand (as you look at the car) contact on the control box, a soft clunk from the dynamo, but no turning of the dynamo.

I've taken off the dynamo and the brushes appear fine, clean and moving freely.

I've checked the wiring connections between the dynamo and the control box and they are all working fine.

I've cleaned the contacts for the control box.

Just as a matter of interest I checked the resistance between the D and F terminals on the dynamo and got no connection. Is that to be expected?

I've not done the 'testing the dynamo in the vehicle' procedure shown in the workshop manual.

The dynamo's not been used for ages, but is pretty new.

Broken field coils?

[svenedin]

The field coils F are not physically connected to the output D with the dynamo off the car. You can measure the resistance of the field coils though by connecting the meter between F terminal on the dynamo and earth. Should be a few Ohms between 3 and 5 ish I think. The fact you dynamo did not work as a motor when you closed the right hand contact breaker on the voltage regulator box does not prove the dynamo is at fault. The voltage regulator could still be the culprit. I would do the dynamo tests as outlined above.

[culp]

I would do the dynamo tests as outlined above.

By that do you mean the 'testing the dynamo in the car' as outlined in the workshop manual?

[svenedin]

I would do the dynamo tests as outlined above.

By that do you mean the 'testing the dynamo in the car' as outlined in the workshop manual?

Yes. You have done the basics. Tried the dynamo as a motor test and it did not work; tested the wiring and it is OK so now test in the car. If the dynamo tests fine it must be the voltage regulator. I wonder why your car had been previously fitted with an alternator? Alternators have their own internal regulator so do not use the voltage regulator. One possibility is that it was done because the voltage regulator does not work! Very often I suspect, alternators are fitted because people think the dynamo cannot provide enough current when in fact the dynamo is fine and the voltage regulator is not.

[culp]

Further developments; I've done the test in the car, no voltage 0v.

The dynamo is pretty new and clean. The brushes move fine but ive not taken them out or investigated further. Do you think its worth changing the brushes, or just bite the bullet and get a new dynamo? I'm inclined to get a new dynamo.

Thanks again for all the advice

[geoberni]

Keeping it simple, carry out the tests in the Lucas Generator and Control Box Tests Manual which you can download here:
https://www.mg-cars.org.uk/imgytr/pdf/lucas.pdf

Parts 1 and 2 are relevant, Parts 3 & 4 are for other Control Box versions.

These are the tests that your garage would have done back in the day. Word for Word, without any risk of someone here telling you how to do it from memory and making a typo or forgetting something.

[svenedin]

Further developments; I've done the test in the car, no voltage 0v.

The dynamo is pretty new and clean. The brushes move fine but ive not taken them out or investigated further. Do you think its worth changing the brushes, or just bite the bullet and get a new dynamo? I'm inclined to get a new dynamo.

Thanks again for all the advice

Has your dynamo ever been fitted on a car or possibly been fitted on a car with a different polarity? I would polarise the dynamo to your car's polarity (I do not know whether you are using positive or negative earth but I assume negative as your car had an alternator). Then once correctly polarised repeat your dynamo output tests. If your dynamo really is dead then you could get a brand new one or (better) get your dynamo properly rebuilt. I can see the dynamo brushes in your photo and they look really new as does the commutator.

[culp]

The car was negative earth with the alternator, but I wanted it to be original, so I've connected it up as positive earth? I'll try that tomorrow and report back. Before the alternator is was positive and the generator sat on a shelf for four maybe five years?

[culp]

Keeping it simple, carry out the tests in the Lucas Generator and Control Box Tests Manual which you can download here:
https://www.mg-cars.org.uk/imgytr/pdf/lucas.pdf

Parts 1 and 2 are relevant, Parts 3 & 4 are for other Control Box versions.

These are the tests that your garage would have done back in the day. Word for Word, without any risk of someone here telling you how to do it from memory and making a typo or forgetting something.

Thanks for this, I love this geeky stuff, I'll have a look tomorrow

[philthehill]

The first thing I would do is polarise the dynamo.
Even new dynamos need polarizing before use.

[svenedin]

The car was negative earth with the alternator, but I wanted it to be original, so I've connected it up as positive earth? I'll try that tomorrow and report back. Before the alternator is was positive and the generator sat on a shelf for four maybe five years?

Definitely polarise your dynamo. POSITIVE earth is original yes. Positive earth means the positive terminal of your battery is connected to earth (to the vehicle body). I am sure your dynamo will be fine. Sitting on a shelf for 5 years is not going to have harmed it.

To polarise for POSITIVE earth, make sure no wires are connected to the dynamo, run a wire from the unearthed terminal of the battery (which in your case is the negative terminal) and touch the wire to the F (field) coil terminal on the dynamo. Repeat touching the wire to the F terminal 2 or 3 times until you see a small blue spark. That's it.

[culp]

I've done that, and still no voltage. Dynamo then?

[oliver90owner]

If the dynamo will not motor, it has a fault.