Hi,

So I'm now sorting out the charging system but i'm having a problem (I think) with the RB310 regulator.

I have downloaded a copy of the original Lucas manual which tells you how to set this up but its still not working.

The RB310 has three connections, battery, dynamo field and dynamo output.

With the battery disconnected I have set the dynamo voltage to around 15v (off load) as the Lucas instructions.

The cut in and out seems to work correctly but there is no charging to the battery and the gauge on the dash only measures a discharge.

I have tried disconnecting the battery connection from the regulator and measuring the voltage at the output terminal on the regulator and get around 3V.

What I believe should happen is that the dynamo outputs 15V at the rated speed (3000 RPM at the dynamo not the engine), the cut in connects it to the battery and the load drags the voltage down to the correct running level (around 13.5V).

With mine the dynamo output measures 15V, the regulator cuts in and the dynamo output stays at 15V and the battery connection on the regulator only outputs 3V.

This would explain why the ignition light illuminates ever so slightly (the light works by supply battery 12V to one side and the dynamo output to the other, when the system is all working both are the same and the light is off, when the dynamo isn't charging it provides a 0V connection and the light comes on.
In my case I have 12V and 15V providing 3V to power the light.

The information I have found on-line tells you how to set one of these units up but doesn't tell you how to diagnose the fault I have.

The later cars may have the RB340 and these are available new for around £20-30 but I would need to change the wiring connections slightly which I would rather not do to my new loom.

Has anyone had any experience with these units? What I would like to do is measure the coils to see if they are within tolerance but I can't find any details of what these should be. There is also a resistor (maybe a shunt?) on the rear of the unit but again I don't have any values to know how to test this.

 

I will try and help and see where we get :-

When the dynamo voltage is lower than the battery voltage, the cut out coil contacts should be open so the dynamo is disconnected from the battery circuit, when the revs rise enough for the dynamo voltage to exceed the battery voltage the cut out coil is energised and the dynamo is connected to the battery.

There are 2 regulators within the unit, one for current and one for voltage, the third coil is the cut out.

If the current draw is too high the field resistor is taken out of circuit to protect the dynamo and the wiring, if the voltage is too high the same happens, the contacts for both these regulators are in series.

The voltage regulation test is checked with the battery disconnected and a voltmeter connected to the D terminal.

Have you done the current test first ? You clamp the contacts of the voltage regulator closed, connect and ammeter from the B terminal to the battery lead and any other leads at this point, turn on the headlights and start the car, the current should raise to about 30 Amps depending on the dynamo fitted (C42) and then remain steady. This proves the current regulator is correct.
Then for the voltage test, lights off, battery lead and ignition leads still disconnected (but joined together), voltmeter connected to D terminal voltage should be between 15 - 15.5 V at 3000 rpm (dynamo)
Finally cut out test.
Reconnect all leads, voltmeter connected to terminal B, should read battery voltage, start the car and slowly increase revs, the voltage should jump up by 0.5 to 1.0 V when the cut out closes, and this should be between 12.7 and 13.3 V, if all these test are ok then all is working fine.

If you can run these tests, and let me know where you have the problem, I will try and assist further. I think the 3V reading is a red herring as I am not sure you are checking at the correct point.

 

I haven't yet carried out the current test as I don't have a suitable ammeter, I have ordered one so that I can check this however, with the battery terminal disconnected and the cut in/out coil engaged the output of the regulator only has a reading of 3V, surely this should be the same voltage as the dynamo input (i.e. 15V)?

With the battery connected to the regulator the voltage at the B terminal is only battery voltage whether the cut out/in coil is engaged or not.

Surely whether the current coil is adjusted correctly or not I should get 15V at the output with no load if that's what I'm getting on the dynamo input to the regulator?

 

I found the diagram below which is for an RB340, these units appear basically the same as the RB310 on my car.

Looking at this (Assuming its correct), it seems that the only things between the dynamo input (terminal D) and the battery output (terminal B) are:

Current limiting winding
Cut out contact

As the cut out contact is working and engaged it seems that it may be the current limiting winding that's at fault, is this the coil winding on the current control and if so any idea what the resistance of this should be so I can test it?

 

That schematic is not quite correct, I will try and find a correct one, the cut out has two windings, one in series with the current reg coil and one in parallel with the voltage coil.

Can you post a pic of the internals of your regulator ?

I will post a schematic later and try and work out how you are getting the 3V reading.

 

The RB310 is very similar to the RB340 but without the swamp resistors, and there are improvements to the contacts to improve temperature variations.

I don't suppose you can get a pic of the underside of the regulator to see what resistors are fitted, some regulator had 2 field resistors others had one.

 

I have had a chance to think about this, first thing to do is clean the cut out contacts, use some fine emery paper, but it between the contacts and then pushing the contacts closed with your finger sand off and clean the contacts.

You could check the resistance between B and D with the contacts pushed shut, this should measure about less than 100 ohms , current coil is approx 60 ohms and the series coil of the cut out is about 10 ohms plus some resistance for the contacts (but hardly any)

Check this resistance before you try cleaning anything, if it is higher, clean the contacts and see what it drops to.

The current and series windings are quite large copper, so it is very unlikely that they will go higher resistance, they would either go short or open circuit.

A high resistance contact would give you a low output voltage, but that voltage would depend on the resistance of the meter you are using to measure the voltage.

I will sketch out, scan in and post a diagram later.

 

I have removed the regulator and had a look at the underside, there is only one resistor and this is between the D and F terminals, it measures around 63 ohms, I assume this is the shunt?

I have measured the resistance across the D and B terminals and it measures 0.6 Ohms with the cutout contact closed.

I've sketched out the wiring diagram which seems to make sense but there are also two small wires, one that comes from the bottom of the voltage coil and is soldered to the case, the other comes from the bottom of the cutout coil and is soldered to the base. I can't see what these do and where they are powered from.

Its all a mystery to me!

 

Got round to drawing up the schematic which is attached.

I hope this helps, the V Reg and C reg are the voltage and current regulator coils, the cut out relay has 2 windings, the lower winding comes into play when current reverses from the battery to the dynamo (i.e. Dynamo voltage is less than the Battery voltage, this reduces the pull on the cut out armature and the contacts open.

The only way you should have 3V at terminal B with the battery disconnected is a high resistance cut out contact, any failure in the current regulator or cut out should fail to close the cut out contacts.

Check the resistance from B to D which should be less than 100 ohms, and from B to earth should be about 9 ohms I am pretty sure.


Just posted this and realised you had already posted. I assume you are measuring open circuit between B and D with the cut out open ? Have you disconnected the D & F connections before you checked the resistance, the reading should not be as low as 0.6 ohms !

With the field windings and armature in parallel with the current reg coil, the reading will be a lot lower.

Start with the basics, disconnect everything, hold the cut out closed and measure the resistance between D & B, B & earth, and F & Earth, then hold open either the voltage regulator or current regulator and measure the resistance between F & earth and let me know what you find.

 

I have found out what the problem is, it seems that although the cut out is moving its not quite making a contact. If I push it further by hand (only a few thou) it makes a contact and then everything works. I have tweaked (bent)the contact and it all works now, however, as I have been messing around with the unit I now need to set it up from scratch.

I can set the output voltage fairly easily (its currently 14.7V off load at the correct dynamo RPM) and I have ordered a meter to check the output current (although this is the only adjustment I haven't touched), however, I need to reset the screw on the back of the cut in/out coil as I adjusted this to see if it would make the coil pull the contact in that little bit further.

The problem is that the cut in voltage is something like 13V and the cutout voltage is less than 11V (I have the exact figures in the garage), however, as soon as I start the car the voltage from the dynamo with the B terminal disconnected is already over 13.5V volts (off load) so the cut in coil instantly connects, I also can't get the dynamo to drop below around 12.5-13V even by turning the idle down as far as it will go so I can't check drop out.

I wondered if I could cheat by altering the voltage setting to temporarily produce these voltages from the dynamo with the B terminal disconnected? Once the cut out coil is set up to the correct voltages I could then wait for it all to cool down and then reset the dynamo voltage to the correct value, although this isn't the Lucas manual way to do it is there any reason this wouldn't work?

In addition I would like to check whether the cutout contact has a required gap? I can't find any information on this?

Finally i'm a little concerned that the connection between the battery and the dynamo is unfused, if the cut out coil fails to disconnect in future when the car is switched off there could be a short potentially damaging the wiring loom. I'm planning to install a 40A fuse between the B terminal on the regulator and the cable to the battery to protect this circuit.

 

Glad you found the issue Homer.

The cut out will always close immediately with the battery disconnected from B, when the dynamo voltage drops below the battery voltage (I know that you have a higher dynamo voltage, this is for explanation) the current in the cut out shunt coil reverses as current tries to flow into the dynamo, this reduces the flux in the cut out armature and breaks the contact. The armature to core air gap should be 35 - 45 thou, this can be set by bending the back stop, then to set the contacts, insert a 15 thou feeler gauge between the armature and the copper shim on the core, press down and then adjust the contacts so they just touch this should set the deflection of the moving contact which should be between 10 and 35 thou. That should set the cut out for initial set up.

The cut-out voltage is more difficult to check, as you need a variable load and ammeter to check it, but as long as the cut in voltage is set the cut out should be fine, you could cheat the voltage regulator to double check the cut in voltage.

If you put some card between the voltage regulator contacts what voltage to you get open circuit from the dynamo ? (battery disconnected)

I always set the voltage regulator whilst under load, with a current draw of between 8 - 10 amps you should get 13.4 to 14.4 V at charging speed.

In real life terms, the cut out may never open whilst the engine is running, but as long as it opens when the engine is off then the battery will not drain.

 

P.S. I don't think you will get the cut out to drop out while the battery is not connected, without the reverse current from the battery I don't think the flux will drop low enough for the cut out to open.

Also just another thought, the 310 contains a bucking coil, this is in series with the current coil, but wraps around the voltage regulator armature this helps smooth out the voltage regulator switching, it doesn't change the circuit diagram as such, but it does add another factor to the operation but not one that effects the setup.