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Alternator warning lights

Hi Folks,

I am planning to replace the original alternator on my DS with an internally regulated one - mainly to get rid of the unreliably external regulator and the rat's nest of wiring which goes with it.

The substitution looks easy but there is one point on which I am not sure. In the original system the regulator box provides a switched earth for the dashboard charging warning light: the bulb is supplied from 12V and earthed through the regulator when the alternator is doing its stuff.

What is the warning light arrangement on a modern alternator? Does the terminal go to 0V when the thing is charging (in which case I can do a straight substitution) or 12V (in which case I need to add a relay)

Thanks in advance.

Ian

Reply to
Ian Johnston
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A standard modern alternator earths the lead from the bulb, so you can just move your existing lead over.

Mrcheerful

Reply to
mrcheerful

Excellent! Many thanks.

Ian

Reply to
Ian Johnston

Beware though that modern alternators rely on the known resistance of the warning light to regulate the charge properly. Lucas alternators used a 2W bulb. This was a common size, so you should be OK, but it is worth checking when you swap the alternator.

Jim

Reply to
Jim Warren

That would be modern as in "rather old".

Reply to
Duncan Wood

In my mind, anything not fitted with a dynamo is modern.

I take your point. But in this context, modern means with an integral regulator as opposed to the OP's external control box.

Jim

Reply to
Jim Warren

: > Excellent! Many thanks. : >

: Beware though that modern alternators rely on the known resistance of the : warning light to regulate the charge properly. Lucas alternators used a 2W : bulb. This was a common size, so you should be OK, but it is worth checking : when you swap the alternator.

Thank you!

Ian

Reply to
Ian Johnston

The ACR series of alternators only use the warning light current to provide initial field excitation. Once charging, there are 3 diodes of the 9 in the diode pack that provide excitation and apply +12V onto the W/L terminal. The warning light is then connected across two terminals at +12V so does not light. The bulb does limit the intial field current but is not particularly critical. The alternator output is controled only by it's own regulator which is in the field return to earth circuit.

John

Reply to
John

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