Dynamo and Control Box problem after rebuild

[johnradrr]

Hi Guys, I have a 1970 Lotus +2 and I did a rebuild of the dynamo because the armature was in badly worn state. But now I am having troubles getting the charging to work. It is either charging off the chart and messing up the gauges, or it is not charging at all.

I also have replaced the 3 bobbin voltage regulator but still having the same problem and now I am stuck what to do.

Could it be a polarization problem? When I put in the new armature did it need to be polarized like they suggest on the MG board: https://www.mgexp.com/forum/1100-and-13 ... g.3294520/

Could a positive polarization cause the Amp meter to go off the scale and over charge the battery? I guess it can - at least the ChatGPT says it can be the problem. But have I now ruined the new voltage meter? I only ran it a short time.

[Craven]

NO polarization is done to set the direction of the residual/initial magnetic field of the stator the fix windings in the body of the dynamo, armature not effected.

[alan.barker]

Imho with a 1970 +2S which has a lot of electric gear it would be best to convert to Alternator.
Alan

[gus]

If it is charging the dynamo is working
If it is overcharging the regulator is not cutting out.

the C40L outputs a whopping 28 amps so there is not a whole lot of risk of overcurrent, but overvoltage can blow things up.

I would closely examine the wiring to see if something is mis connected
Then I would remove the lot and smash it to tiny bits with a large hammer
Defective regulators can burn a car to the ground in the rare instance the battery has enough charge to generate that much heat
An alternator is always the right answer
Power windows with a generator
fuggetaboutit

[alan.barker]

After many years i fitted a n Alternator to my Sprint and at last i have Indicators that work correctly. I can switch things on when i need them and be safer. I can stop telling swmbo not to use the Electric Windows tooo much.
Wow i was soo stupid not to fit the Alternator before. An ACR 17 Lucas type which in it's day was an option so doesn't look wrong. 45 Amps on tap what a difference. I gutted the Voltage Control Unit and used to connect and hide Cable Joints.
Replace the Ammeter with a Voltmetre so NO high current running behind Dashboard ( safety first).
Alan

[johnradrr]

Unfortunately I'm not up for the conversion to alternator because I am only driving about 500 miles a year and there just is no need. But according to the AI if I changed the armature it needs to be polarized - but you are saying it is not true?

So perhaps I have to check the connections again...

This is the dynamo: https://photos.app.goo.gl/FGhtFN3o47hi7MzY7

So the F connector on the top is going to the F connector on the voltage regulator and the "small" connector on the dynamo is going to D terminal?
https://www.homemade-circuits.com/wp-co ... ulator.jpg

What AI says:
Yes, if you have changed the armature in the dynamo, it is essential to polarize the dynamo before use. Here’s why and how to do it:

Why Polarization is Necessary
Residual Magnetism:
Dynamos rely on residual magnetism in their field coils to start generating current. Changing the armature can disrupt this residual magnetism.
Correct Polarity:
Polarization ensures that the dynamo’s magnetic field is aligned correctly with the car’s electrical system, matching the vehicle's ground (positive or negative).

[Andy8421]

John,

Just to be clear about the terminology, a dynamo is effectively two bits, a static bit - the dynamo outer case that bolts to the car - this is called the 'stator'. The bit that goes down the middle that spins is called various names (armature is one) but the most common is 'rotor'.

So, in an Elan, the dynamo relies on residual magnetism in the stator to get going. The rotor is deliberately designed not to have residual magnetism. This residual magnetism has to be the 'right way round' to match the polarity of the car (negative or positive earth) or the dynamo never manages to pick itself up by its bootstraps and get going. This residual magnetism can easily bet set the right way around by flashing a wire connected to the battery on the to the terminal on the stator (often marked F for 'field windings').

In your case, replacing the rotor should have had no effect on the residual magnetism of the stator. As it would appear your dynamo is generating an output, it is unlikely to have anything to do with residual magnetism.

Your dynamo picture is however worrying for a couple of reasons, the wiring looks in a poor state, and also looks wrong. The big terminal at the back of the dynamo should have a thick cable, usually brown or brown/yellow that runs to the 'D' terminal on the regulator. The small terminal (on the side of your dynamo) should have a thinner cable, usually brown/green that runs to the 'F' terminal on the regulator.

If you are unsure about this, please get someone with experience of car electrics to look at the wiring for you. The wiring is marginal at best in the Elan and has caused many fires.

[2cams70]

That’s a bit of a strange Lucas C40 dynamo where it appears that the field connection is on the side of the dynamo housing rather than through the rear end plate. Never seen that before. Perhaps it’s unique to the Elan application.

As I understand it you only had the problem after you removed the dynamo did something to it and then replaced it. This would suggest that there is unlikely to be anything wrong with the original regulator and the problem is more likely to be due to something you did during the dynamo repair procedure. To eliminate the possibility of a faulty new regulator you should replace the new regulator with the original for diagnostic purposes.

What did you do to the dynamo when it was removed? Replace the armature with a new one? Just resurface the commutator? Replace the brushes?

Did you remember to release the brush springs after final assembly? Otherwise the brushes won't make proper contact with the commutator.

[johnradrr]

To clear up a few things... the dynamo armature was replaced with a new one and the brushes fitted with new ones -the springs of course released. We tested the dynamo by hooking it up to a power drill and running it with an voltage meter connected and it produced just fine electrical output in the 12V-16V range at high speed. So I know the dynamo is working.

The original control box had the Amp meter bobbin plate (is it called the cutout relay?) stuck so it was for sure bad.

The wiring has been as it has been for 10 years and working without a problem up until the brushes went bad and the armature was so grooved I decided it needed to be replaced. I need to again check the wiring and be sure I have the right connections. But if I had the D and F connections reversed is this going to cause more Amperage to go to the battery? Seems a bit odd that this would be the case. I will also see can I replace the wiring with more heavy duty wire for the big terminal, but I doubt this is really the problem as 10 years with this wire and no problems, I just can't see it is really this.

I need to confirm the connection and then try a repolarization if that is not helping.

[alanr]

Just a thought...
Have you checked that the earth/ground is good from the 'E' terminal on the RB340 Regulator? It won't charge if either it is not connected or not good.

Alan.

[Craven]

Section 4 gives you the tests you need.
viewtopic.php?f=50&t=41661

Generators
lucascourse4.pdf
Generators
(1.27 MiB) Downloaded 1321 times

[gus]

Power output wire looks too small
But that is not the issue if you are getting over charging
The regulator is misconnected/misadjusted/malfunctioning

[2cams70]

If the problem wasn’t there before you put the new regulator in put the old one back double check the wiring and see how you go.
As a tip for wiring I always take photos before I remove or dismantle something associated with a lot of wires

[johnradrr]

OK yesterday with a friend of mine (used to be a mechanic in the 60s) we tried to again solve the problem but no luck. I have now had two control boxes, they both are the BOX 81824174 / K900136. But both had the problem of when connecting up to the rebuilt dynamo the points on the AMP bobbin getting severely burnt and smoking - so I believe those control boxes are dead or what does everyone think?

When I connect up the system and turn the ignition I do not get the red light for the battery in the car, which again tells me there is something wrong.

I am now going to do a test today of the dynamo in the car according to this method to see if I can see what it is actually outputting: https://www.howacarworks.com/electrical ... ing-output

But I am at a loss as to what else to do. I guess I have to get another control box, and I can get a 3-pole controller RB340, which is slightly different but should be nearly the same as what I tried. But maybe I somehow shorted the box or crossed a wire when first hooking it up and this destroyed the box and now is causing my problem, could it be?

What about the armature that I replaced? Could it be this is the wrong type and outputting too much voltage? I replaced mine with this one https://gyazo.com/86fa08340aa21e2cbbb9ffd87408a264
Not sure are they all the same or not, and there was not info about it on the site I bought it from.

Anyone have any ideas?

[gus]

If two regulators have both ended up with burnt points, the odds that they are both bad are vanishingly small.
The odds that it is incorrectly connected are significantly higher