Dynamo/Ignition Light - What Am I Missing?

[cbjroms]

I have a Herald 13/60 but I suspect that my plea for help will make sense to more than just Herald owners.

The large connector (F) on my Dynamo is connected to F on my Control Box. The smaller connector (D) is connected to D on my Control Box. D on the Control Box is also connected to my Ignition Warning Light, the other terminal of which is connected to power. With the ignition key in first position the Ignition Warning Light is on, problem is it stays on permanently at whatever revs the engine is at!

So, I have tested the Dynamo by removing fan belt, putting a jumper between its two terminals and applying power - it runs like a motor. I then put the fan belt back and ran the engine with a voltmeter connected to the jumper and was getting 20V at idle. So the Dynamo is working well?

I am not sure what terminal D on the Control Box actually does but I am wondering whether it just provides a convenient way to 'splice' the wire from D on the Dynamo with the wire from the Ignition Warning Lamp. Or is my problem due to a Control Box fault?

[RobPearce]

Your problem is that you've not got it wired right. Check out the proper wiring diagram in the workshop manual.

Dynamo 'F' (big brown/green wire) goes to control box 'F'

Dynamo 'D' (small brown/yellow wire) goes to control box 'D'

Control box 'WL' goes to warning lamp (confusingly also a brown/yellow wire)

Control box 'B' is the one with two terminals, and three brown wires to battery, lights, ignition switch et. al.

[glang]

yes as you say the dynamo looks ok and the problem is with the regulator or wiring. You have battery voltage on one side of the ignition light and this pushes current through it via the regulator until the dynamo produces more than that voltage on terminal D and the current can no longer flow so the light goes out. 

First to check is the wiring continuity between the reg and dynamo as the reg should supply power from terminal F back to the field winding of the dynamo so that its output voltage increases to terminal D.

Its a loop so that regardless of revs the dynamo output voltage increases until its reaches the set point and the reg contacts open.... 

[cbjroms]

Thanks guys,

I have wired-up the car with reference to the wiring diagram in the Haynes Manual. The Control Box has 5 labelled connections: E, F, D, A & A1. There is no WL? The letters are quite difficult to see on the diagram but seem to read as follows to me:

Dynamo 'F' (big brown/green wire) goes to control box 'F'

Dynamo 'D' (small brown/yellow wire) goes to control box 'D'

Ignition switch (brown/blue wire) goes to control box 'A1'

Ignition Light (small bown/yellow wire) goes to control box 'D'

Ground (black wire) goes to control box 'E'

Just to be clear, the Ignition has live 12v feed into one terminal of the lamp and the other wire is the one that goes to control box 'D'.

So I am still struggling to see what I have got wrong?

[RobPearce]

Quoted from cbjroms-

 The Control Box has 5 labelled connections: E, F, D, A & A1. There is no WL?

Sorry, my mistake - I was looking at a Vitesse wiring diagram. Apparently the 13/60 used a different control box.🤔

[cbjroms]

Sorted it. I had these the wrong way round:

Dynamo 'F' (big brown/green wire) should be to 'D'

Dynamo 'D' (small brown/yellow wire) should be to 'F'.

 

[glang]

Are you sure youve got your labelling right? In my Vitesse manual (cant believe the dynamo is much different) it shows the big terminal as D and small one F. Then big brown/green wire goes from to D on the reg and the small brown/yellow to F which makes sense....

Either way youve got it correct now and youre up n running👍

[Saltddirk]

The letters on the control box should be seen as to what connect to it.

D is the feed from the dynamo, it should be the biggest wire, normally brown/ green , brown or yellow ( color code changed a bit over the years). When your generator starts spinning the armature starts rotating between 2 magnets. This is generating a current which is harvested at D

F goes to the field windings, it is this wire that carries the current to engergise the coils in the magnets and thus provide the magnetic field that  will generate the output. It is the smaller of the wires and normally yellow/ brown.

A is the regulated output and connects to the Ampmeter (if there is one) and then through to the starter solenoid and Battery. A carries all the loads to and from the battery. There is no fuse in this circuit, ie it is always life as soon as the battery is connected. 

A1 is also a regulated output but only carries the loads to the ignition switch and the lighting switch.

A3 also connects up to the ignition switch, but on the return side, ie is only live when the ignition is on. Where A and A1 can be seen as outputs from the regulator/ Dynamo, A3 can be seen as input for the other circuits

A4 is a fused spur on A3, ie it is only live when A3 is live and is where all your auxilliary circuits would be hooked up to. 

if there is a WL terminal that is where the warning light is hooked up to. if there is none the yellow from the WL should be connected to D. This only when you are still using a Dynamo, not when you are using an Alternator

The warning light would normally get a 12 V input from the ignition switch (white wire) and then connect up to the generator output (originally also yellow) . With the generator stationary and thus no output this terminal is earthed, so the current would flow from the battery to the ignition switch and then through the lamp to earth, as a result the lamp lights up. As soon as the generator starts spinning there is a current generated and the terminal not longer is earthed but now carries voltage, the voltage across the lamp slowly drops until it reaches 12 volt and with the same voltage each side the lamp goes out.

If the dynamo has been replaced with an alternator then the regulator is effectively redundant, as the voltage is regulated inside the alternator and not by the control box. In that case the warning light should be connected direct to the small spade terminal on the Alternator ( or spliced to it) Principle is the same but here the small terminal carries the voltage sensing which is used internally to produce the 12 volts. 

In Lucas speak 

Brown would be current supply and feed to all circuits, Blue would be head lamp circuit, Red would be tail  and side lights circuit, white ignition, Purple would be all these circuits fed from fuse A2 on the control box and green all those Auxilliary circuits fed from A4, yellow as said before for the generator wiring and Black for the earth returns.

However over the years with the circuits becoming more complicated the distinctions became vague. and several owners and wanabe car electricians later you can not longer trust the simple logic, better is to get your multimeter out and check where the wires connect up to.

D