Ignition Warning light - wiring with an alternator

[Pete Bags]

Hello,

The wiring loom in my '63 Minor has seen better days - already I have had to run a new wire from the main headlight beam supply to the speedo as the blue high beam tell tale lamp did not work, I'm assuming the original wire somewhere in the loom has failed.

While I've got the speedo out, I am also trying to get the ignition warning light to work (it hasn't worked for ages!) and again I'm suspecting a wire in the loom somewhere has come adrift. I have checked all the bulbs and the bulb holders, they are fine. My car has an alternator, so if I run a new pair of wires to the ignition warning lamp, where would the source be from? I know one is an earth, but I'm unsure of the other!

I have replaced all of the speedo bulbs with LED ones from Classic Car LEDs - interestingly, they said don't put an LED bulb in ignition warning light, as that could cause battery charging issues - but is that only for dynamo/voltage regulator equipped cars?

Many thanks in advance for any pointers!

Pete

[svenedin]

The ignition warning light has two connections (it does not connect to earth). One is a white wire from the ignition switch (assuming your 1963 is key start) and the other is a brown/yellow wire from terminal D of the RB106 control box. At least that is how it is with the original wiring and a dynamo. As far as I know, an LED cannot be used for the ignition warning light and it must be a standard incandescent bulb. This is because the LED is a diode that only allows current to flow in one direction. The ignition warning light must be able to allow current to pass in either direction. The light works by staying off when the battery voltage and the charging voltage are equal. When there is less voltage from the charging system than the battery the light is on (such as when the ignition is on but the engine has not been started or the engine revs are low).


Stephen

[jagnut66]

As far as I know, an LED cannot be used for the ignition warning light and it must be a standard incandescent bulb.

Agreed 100%.
I found out the hard way, when I changed all my dash illumination to LED and did the warning light at the same time, so it would be brighter.
Big mistake, my battery kept going flat!
The rest of my dash illumination is still LED's except this, which once I was informed of this issue, I swapped it back to a standard bulb.
Problem solved.

The wiring loom in my '63 Minor has seen better days - already I have had to run a new wire from the main headlight beam supply to the speedo as the blue high beam tell tale lamp did not work, I'm assuming the original wire somewhere in the loom has failed.

......and again I'm suspecting a wire in the loom somewhere has come adrift.

Time for a new loom I think.
With all these issues and doubtless more will arise over time, surely it will be allot less hassle and stress to just renew the whole thing.
Best wishes,
Mike.

[geoberni]

I am also trying to get the ignition warning light to work (it hasn't worked for ages!) and again I'm suspecting a wire in the loom somewhere has come adrift.

Quite honestly, I'm at a loss to understand how the alternator has been working if the Warning lamp is dead.... I'm wondering how the Alternator conversion has been connected.....

Personally, I think it's time you replaced the wiring loom before the car catches fire......

[Bill_qaz]

20230622_155206.jpg (265.47 KiB) Viewed 6245 times

Most modern alternator will still charge with a failed ign warning light as it doest need it to excite.
As said ign switch feed to warning light and other side to w/l small spade on alternator( highlighted in pic) it doesn't need control box connection.
Check alternator terminal is ground when stationary ( earth for dash warning light) and positive when running ( two opposing positive to put light out)

[Pete Bags]

Many thanks for your replies!

Stephen - my ignition switch is that alone, as the car has the pull knob to engage the starter - perhaps the ignition switch is playing up (a bit like yours did!)?

Bill, Jagnut and Geoberni, thanks for the pointers, I'll check the alternator wires! A loom replacement is high up on my list of 'things to do' in the winter months - a task I'm not particularly looking forward to, but it needs to be done!

[svenedin]

Many thanks for your replies!

Stephen - my ignition switch is that alone, as the car has the pull knob to engage the starter - perhaps the ignition switch is playing up (a bit like yours did!)?

Bill, Jagnut and Geoberni, thanks for the pointers, I'll check the alternator wires! A loom replacement is high up on my list of 'things to do' in the winter months - a task I'm not particularly looking forward to, but it needs to be done!

Things to check

1) White wire from ignition switch. This is the same whether pull start or key start
2) Brown/yellow wire from alternator to ignition warning lamp. As the original wire from terminal D of the RB106 would be too short, this may have been extended in the wrong colour wire. You will find the original wire near to where the RB106 was (if this has been removed).
3) Fit an incandescent bulb (not LED) to the ignition lamp holder

Stephen

[Pete Bags]

Thanks Stephen - I’ve fitted my new LED bulbs, keeping the ignition one an incandescent. I also replaced the indicator bulb with a green LED, much easier to see even in bright sunlight.

Will check the wiring when the temps come down!

[Bill_qaz]

Many thanks for your replies!

Stephen - my ignition switch is that alone, as the car has the pull knob to engage the starter - perhaps the ignition switch is playing up (a bit like yours did!)?

Bill, Jagnut and Geoberni, thanks for the pointers, I'll check the alternator wires! A loom replacement is high up on my list of 'things to do' in the winter months - a task I'm not particularly looking forward to, but it needs to be done!

Things to check

1) White wire from ignition switch. This is the same whether pull start or key start
2) Brown/yellow wire from alternator to ignition warning lamp. As the original wire from terminal D of the RB106 would be too short, this may have been extended in the wrong colour wire. You will find the original wire near to where the RB106 was (if this has been removed).
3) Fit an incandescent bulb (not LED) to the ignition lamp holder

Stephen

Stephen why would the wire be short the warning light and dynamo output go to terminal D on the RB106.
That wire now goes to W/L on alternator instead of dynamo, same position, so cable length is the same. The alternator out put doesn't use the RB106 as its self regulating.

[svenedin]

Many thanks for your replies!

Stephen - my ignition switch is that alone, as the car has the pull knob to engage the starter - perhaps the ignition switch is playing up (a bit like yours did!)?

Bill, Jagnut and Geoberni, thanks for the pointers, I'll check the alternator wires! A loom replacement is high up on my list of 'things to do' in the winter months - a task I'm not particularly looking forward to, but it needs to be done!

Things to check

1) White wire from ignition switch. This is the same whether pull start or key start
2) Brown/yellow wire from alternator to ignition warning lamp. As the original wire from terminal D of the RB106 would be too short, this may have been extended in the wrong colour wire. You will find the original wire near to where the RB106 was (if this has been removed).
3) Fit an incandescent bulb (not LED) to the ignition lamp holder

Stephen

Stephen why would the wire be short the warning light and dynamo output go to terminal D on the RB106.
That wire now goes to W/L on alternator instead of dynamo, same position, so cable length is the same. The alternator out put doesn't use the RB106 as its self regulating.

Yes you're right Bill. What I meant was a brown/yellow wire from the dynamo goes to terminal D of the RB106 and another brown/yellow wire goes to the warning light. Terminal D is acting as a junction. If the RB106 has been removed when the alternator was fitted, these two brown/yellow wires need to be joined as they originally were at terminal D. Otherwise the warning light is not connected even if the original brown/yellow wire is connected to alternator correctly.

I think driving over 100 miles today top-down in blistering heat has fried my brain! Still there is no respite. It's incandescent inside the house.

Stephen

[Bill_qaz]

Don't know why my colours are different the warning light wire from alternator is yellow with green and and is connected to warning light wire near the RB106. The alternator output is heavier cable solid yellow and is bridged to A terminal at the RB106. They do look like OE wires.

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[svenedin]

Don't know why my colours are different the warning light wire from alternator is yellow with green and and is connected to warning light wire near the RB106. The alternator output is heavier cable solid yellow and is bridged to A terminal at the RB106. They do look like OE wires.
20240323_125856.jpg

Bill, yes. It depends on which wiring diagram in section N of the workshop manual you look at. It appears the colour of the wires were changed at some point from yellow to yellow/brown. I can't find a diagram showing yellow/green going to terminal D though so that's a bit strange unless I'm looking at the wrong wiring diagram. Some early cars had yellow/green going to from terminal F to the dynamo and green/yellow was used in later cars going to the heater! The OP needs to look at the exact wiring diagram for his year of car.

Stephen

[Bill_qaz]

Yes always difficult to be exact with colours on someone else's car, so many variations over the years and some unrecorded.
Remember the post about oil pressure switch and filter block switch wiring colours.
I tend to just meter out connections and have done all the accessories wiring myself but must be difficult if you are not into electrics. Its also difficult trying to advise online when you can't see the car, but I hope we have helped the OP with his problem.

[svenedin]

Yes always difficult to be exact with colours on someone else's car, so many variations over the years and some unrecorded.
Remember the post about oil pressure switch and filter block switch wiring colours.
I tend to just meter out connections and have done all the accessories wiring myself but must be difficult if you are not into electrics. Its also difficult trying to advise online when you can't see the car, but I hope we have helped the OP with his problem.

Bill, totally agree. I am no whizz with electrics having only basic schoolboy knowledge. The most useful thing to me is a multimeter with a continuity function and a beeper. With this I can trace wiring quite easily. If the multimeter leads are too short they can be extended. Sometimes it's easier with two people but crocodile clips can help too.

Stephen

[Pete Bags]

Hi all,

I'm still struggling to get my ignition light to work - primarily as the wires to the ignition light, that come out from the loom, are different colours to the wires on the alternator - all three of which go into the original loom. The wires from the ignition switch also disappear into the loom, so I think my next task must be to check using my meter if there is a direct link from any of the wires in the switch and alternator, back to the warning light - am I missing anything obvious?

Edit - for some reason it's displaying multiple images of the alternator even though I only posted it up once - mods?

This image below shows the three wires that come out of the back of the alternator:

alternator

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This image shows the warning light, with a white and yellow wire feeding it:

alternator

IMG_9265.jpeg (164.44 KiB) Viewed 2666 times

This image shows two white wires coming out of the ignition switch and going into the wiring loom:

alternator

IMG_9265.jpeg (164.44 KiB) Viewed 2666 times

[svenedin]

OK. This is not difficult.

As I said, the ignition warning light has a white wire and a brown/yellow wire going to the bulb holder. This you clearly show in your photograph (or maybe there a shadow in the picture anD it's just yellow not brown/yellow). The white wire going to the bulb holder goes to the ignition switch. Make sure it is connected electrically by using the continuity function on a multimeter.

The brown/yellow wire connects to the brown/yellow wire you show coming from the alternator. Trace the brown/yellow wire from the alternator and it must have a junction somewhere near where the RB106 regulator was or still is.

Stephen

[geoberni]

Edit - for some reason it's displaying multiple images of the alternator even though I only posted it up once - mods?

Well looking at it, the 3 images of the Alternator appear to have been "Place Inline", while the other 2 images are 'Attachments' as indicated by the white box around them (and the word ATTACHMENTS on each one )

Like this:

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20260612_153207.jpg (213.45 KiB) Viewed 2545 times

You probably can't open it to 'Edit' given the time that has passed, but you can see in this screenshot example that the Fan Blade Image has been placed inline 2 times, while the 2nd image is left in the Attachments box and that get the white line around it.
As is this screenshot....

[Bill_qaz]

While you are circuit testing a suggested by several replies.
When using continuity test with a multimeter the circuit tested must be not live.
If you want to test a live circuit you must use -V with meter neg on known good earth or direct to battery earth and pos on live circuit.
Have you made sure your alternator body has a good earth, via its mounting to the engine block the engine must have ground if your starter works.
Post a picture of the RB106 and its connections, it will only be used as a junction as you alternator is internally regulated.
With ign on put a jump wire from ground side of warning light to a good earth, does the bulb light, if yes put a jumper wire from same point on bulb to the warning light terminal of the alternator.
If bulb lights it a wiring issue if bulb doesn't light the its an alternator fault.
I had an alternator that did not ground the bulb but charged perfectly, replaced alternator and all good.will repair old one as a spare.

[Pete Bags]

Hi everyone,

Many thanks for all your replies - hopefully the next time I post some pictures, I will get it right!

I now have to admit to eating some humble pie - I followed your suggestions and checked for wiring continuity and 12v connection - all checked out. I also checked that the alternator was earthed properly - but still no working light. Finally I thought I should check the bulb.... It had blown! I put in a new bulb and now all works as it should.

Moral - check the obvious first!

Pete

[svenedin]

Hi everyone,

Many thanks for all your replies - hopefully the next time I post some pictures, I will get it right!

I now have to admit to eating some humble pie - I followed your suggestions and checked for wiring continuity and 12v connection - all checked out. I also checked that the alternator was earthed properly - but still no working light. Finally I thought I should check the bulb.... It had blown! I put in a new bulb and now all works as it should.

Moral - check the obvious first!

Pete

At least it's all fixed now!

Stephen