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battery warning light
dan-g - 18/4/12 at 09:52 AM

hi, its me back again with another problem!
our wiring isnt what you'd call perfect but our main concern is the wiring of the alternator and the battery warning light.
can someone guide us to a definate wiring line from alternator to bulb to battery etc?! thanks in advance

nib1980 - 18/4/12 at 09:57 AM

depends a bit what your alternator is?

nib1980 - 18/4/12 at 10:00 AM

try this if it applies to your type

http://westfield-world.com

http://westfield-world.com/Wiring_files/Wiring_frames.html

Alan M - 18/4/12 at 10:05 AM

As far as I am aware, it should be like this:

3 pin Connector on back of alternator containing:
IG terminal: Voltage in from ignition switch to power alternator
S terminal: Senses charging voltage
L terminal: used by regulator to ground warning lamp

Therefore the warning light has a switched live supply from the ignition circuit which is earthed from terminal L when engine is not running.

mikeb - 18/4/12 at 10:11 AM

sorry to jump on this can anyone tell me the wiring for the ford sierra alternator.


IMAG0368 by mjb22001, on Flickr

I have the thick cable going back to the battery +ve.
I thought the w terminal was to the bulb that then connected to a switched live.
The other terminal I thought was just a +ve from the battery also.

With the smaller gauge +ve connected to the middle terminal the light doesn't come on with the ignition. If I remove the middle terminal the light comes on but stays one when I start the engine.



[Edited on 18/4/12 by mikeb]

mikeb - 18/4/12 at 10:41 AM

Internet suggests this for the sierra alternator (which doesn't tie up with the wiring diagram I looked at in the haynes manual)

B+ thick wire to battery
D+ to warning light
W is a 8 or 12v output for autochoke

I'll give this layout a go
and leave W disconnected.

How does the alternator get its sensing voltage for charging? with this arrangement?

[Edited on 18/4/12 by mikeb]

[Edited on 18/4/12 by mikeb]

mikeo632 - 18/4/12 at 11:06 AM

Hi.
The following is an extract from info that i got from the web & following this, my warning light works ok!

The warning light is like a pair of balance scales between the ignition circuit and the charging circuit, and that is how it is connected - from the white of the ignition circuit, through the bulb, and to the dynamo/alternator via the brown/yellow. (Note that the lamp-holder is unique in that it has two wires - one to each side of the bulb - and the body of the holder should not be connected to ground like the panel lamps are.) If both circuits have the same voltage then there is no potential difference across the bulb and it will not light. This is irrespective of whether there is 0v on both circuits (ignition off, engine stationary) or 12v (actually around 14v when charging) on both circuits (ignition switched on and engine running and charging). If the two circuits show a potential difference i.e. ignition switched on but engine stationary or ignition switched on and engine running but not charging, then the lamp will light. This latter condition is a fault (and incidentally the main purpose of the light) which should be investigated before you get stranded. You may also note that when you switch off the ignition but while the engine is still spinning the ignition warning light glows again until the engine stops.

Hope it helps.

dan-g - 18/4/12 at 11:36 AM

we'v a 1.8 cvh with a lucas alternator that has the 3 connectors on the top of the alternator. what iv found is a circuit that runs like: alternator earth via engine-middle pin on the alternator-bulb-ignition live
but in doing that we end up having a battery-less systen as the alternator keeps the coil running, could it be our coil wiring thats at fault??

mikeb - 18/4/12 at 11:52 AM

dan it should be the same alternator as mine as mines a 1.8 cvh.

snowy2 - 18/4/12 at 12:37 PM

This exact question was asked and answered by myself and others only a few weeks ago.

dan-g - 18/4/12 at 01:23 PM

quote:
Originally posted by snowy2
This exact question was asked and answered by myself and others only a few weeks ago.


http://locostbuilders.co.uk/viewthread.php?tid=167876

is that the thread you're refering to??
the lucas alternator we have has a large red wire(from battery), a small blue wire and a blue/white wire, all on top of the alternator with 3 seperate nuts
from what i'v read the middle wire(blue) is the 1 that goes to the light??

mikeb - 18/4/12 at 02:07 PM

dan, its the same alternator as mine,

My post a few up in this thread said where they go.
The middle one is to the bulb.

dan-g - 18/4/12 at 02:27 PM

quote:
Originally posted by mikeb
dan, its the same alternator as mine,

My post a few up in this thread said where they go.
The middle one is to the bulb.


its the rest of the loom from the middle post on the alternator that we'r stuck with, does it go to the bulb and the other terminal of the bulb go to an ignition live??
if we were to use an external bulb, just a couple of wires going from alt' middle post to bulb to ignition live should the bulb come on and off as it should??

mikeb - 18/4/12 at 02:36 PM

yep thats my understanding.
One end of the bulb to the middle post the other end to a switched live.
When the engine is not running the switched live provides 12v to the bulb and is earthed through the alternator body (assuming your engine is earthed to the chassis and back to the -ve battery) hence the light comes on.

When running the middle post provides 12v cancelling out the 12v from the switched live, hence no light.
Thats the theory.

[Edited on 18/4/12 by mikeb]