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
--

"Ian Johnston" <ian.groups (AT) btinternet (DOT) com> wrote

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

Mrcheerful

On Fri, 30 Jun 2006 15:19:10 UTC, "mrcheerful
."
<nbkm57 (AT) hotmail (DOT) com> wrote:

:
: "Ian Johnston" <ian.groups (AT) btinternet (DOT) com> wrote in message
: news:cCUlhtvFIYkV-pn2-wV0BPFL88bVI (AT) localhost (DOT) ..
:
: > 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)
:
: A standard modern alternator earths the lead from the bulb, so you can just
: move your existing lead over.

Excellent! Many thanks.

Ian

Ian Johnston <ian.groups (AT) btinternet (DOT) com> wrote


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

On Sat, 01 Jul 2006 08:05:14 +0100, Jim Warren
<jimwarren (AT) OMITblueyonder (DOT) co.uk> wrote:


That would be modern as in "rather old".

Duncan Wood <nnipnews (AT) dmx512 (DOT) co.uk> wrote

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

On Sat, 1 Jul 2006 07:05:14 UTC, "Jim Warren"
<jimwarren (AT) OMITblueyonder (DOT) co.uk> wrote:

:
: Ian Johnston <ian.groups (AT) btinternet (DOT) com> wrote in message
: news:cCUlhtvFIYkV-pn2-74tdu43dKVS5 (AT) localhost (DOT) ..
:
: > : A standard modern alternator earths the lead from the bulb, so you can
: just
: > : move your existing lead over.
: >
: > 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

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