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Isuzu alternator wiring


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This in the plug on the back of my alternator, I think the wires are;

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  1. Tacho
  2. Lamp
  3. Sensing

The colurs are;

White (thick wire)

White and red (thin)

Black and light yellow (thin)

Which one is which? Am guessing the sensing wire is the thickest but do not know which of the other 2 go to my lamp.

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The following pics and quote are for a different Isuzu diesel engine and vehicle to what I'm guessing your alternator is off, but may help.

The alternator connections are very simple. The standard Isuzu alternator has an integral regulator which makes it even easier to wire up. Check Fig. 9 on page 6D-14 of the FSM for detailed wiring.

Basically, you have three wires going to a round connector on the back of the alternator plus a heavy black wire (B) going to the output stud also on the back of the alternator. This black wire should be heavy enough to handle the full alternator output (70 A) and goes directly to the (+) of the battery (might be a good idea to protect it with a fusible link or big fuse). The black wire (S) from the round connector also goes directly to the (+) of the battery. It serves to sense the actual voltage at the battery which the regulator uses to control the output voltage of the alternator. The white wire (IG) from the round connector goes to the ignition switch and should be hot only when the ignition switch is in the "run" position. This wire turns the charging system on and off. The white with blue stripe (L) is used to control the "Charge" indicator light and is optional. When the alternator is charging, the (L) wire is hot and turns on the "charge indicator relay". Since the indicator light is wired through the normally closed set of contacts on the relay, when the relay is turned on, the indicator light goes out. Hope that makes sense.

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Isuzu IIRC is or was part of GM, a good auto electics place should be able to advise further.

My understanding is that GM bought approximately 1/3 of Isuzu at some stage but most of the benefit went to GM and AFAIK Isuzu have bought all or most of that back. GM rebadged some Isuzu vehicles and sold them in several countries.

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Thanks for an excellent answer, I almost got there, found a voltage regulator diagram (below) which appears to be my 3 pin plug. Also coincides with yours so explosion could be averted!

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The thing with tach then is red herring, this may then come off fuel pump - more googlisation then! This may be one for the technical archive as I know a number of people have had problems with Isuzu alternators and others have run theirs accidentally in the non-sensed mode so overcharged their batteries, either using water or totalling the battery. I think this alternator is also used in a number of marine applications possibly fitted to Yanmar diesels.

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More info posted by Gribble on ITOCUK

Most of the alternators on troopers are hitachis and as such are load sensing so on the wires the two larger ones are the outputs and one goes to the main supply board and one to the starter main terminal.

The smaller one is the charge light or L line which when the key is at ign on earths the batt light but once the alt starts to charge it 'switches ' the earth off and via a relay the batt light goes out.

So take your ign feed from the batt light and wire it through a relay to the alt and all should be well , I can post a pic for you to help if you are not keen on electrics

If you are going to fit a winch I would put the output wire onto the batt direct as it keeps the winch motor speed up

On the injector pump you only need a key switched live to the stop solenoid as the other bit is the CSD or cold start which its never cold enough for in the UK

Making more sense now, mind the generous swigs of cheap scotch may have played their part...

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your tacho feed is on the fuel pump, i've written about the wiring for the isuzu tacho on another post somewhere. the cable colours are black and red if i recall. the signal actually comes from the earth.

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your tacho feed is on the fuel pump, i've written about the wiring for the isuzu tacho on another post somewhere. the cable colours are black and red if i recall. the signal actually comes from the earth.

Cheers Callum,

Not a priority just yet but might hook a tacho up later on my list of things to do with the P38 box mod.

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  • 2 months later...

An older alternator usually only has two wires...

A modern (like this millenium) battery-sensed jobbie will have three (12V out, charge warning out and sense wire), and won't charge properly unless the sense wire is connected to the battery, IIRC.

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The alternator on the Audi is a modern thing (ive got three, one bosch and two valeo) and it just has two, one bolted fixing for output and the sense/warning wire to the dash.

I think the sensing is still done via the charge indicator lamp?

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Right then I am guessing that you are talking about the 3 wires that come of the back of the alternator at the top from the plug?

You should have:

Black with white stripe - This goes to the Yellow/Brown wire in the Land Rover

White with red stripe - This goes to the Red/Yellow wire (sense wire)

Solid White - This is your extra wire just run a new wire from this and connect it to the back of the Starter Motor

The other thicker wires coming off the bottom of the alternaor (can't tell the color too much muck and electrical tape), these should connect to your thick brown wires in the Land Rover.

Having said all this I connected the sense wire on mine and it just melted it, I never bothered changing it and reconnecting it and all charges and works fine.

Hope this is of some help. :D

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