Alternator wiring

I'm getting a tad confused here, so a little help is needed.

Firstly, the landy has no original wiring left, it's all gone, i've replaced most of it and still working through other areas over the next few days.

My issue i'm stuck with is the alternator and it's role as a charging system, i've googled, looked on here and come up with a few answers but i'd like a nice definate answer if anyone can help as some answers don't quite add up to what i need to know.

I have an alternator ( from a 19J engine, bolted to the 200tdi block ), this has 3 wires from the rear.

• 2 of these wires ( thick brown ones ) go to the starter motor, is this correct? I'm assuming it is as that's what the old one's did before i removed them.
  
  
  
• the 3rd wire goes into the dash area, and here it stays at the moment as i can't work out what i'm trying to acheive with it.
  
  
  
• From what i can gather ( i could be wrong ) is this cable goes to a light ( charge light ) from there it then goes on to the ignition ( switched, ie on first turn ) , but where after that? Is the point of this 3rd smaller wire to provide 12v to the alternator to get it to begin charging?
  
  
  
• I have a volt meter in the dash, this reads 12v when the engine is running, usually it's over 14v, but as i'm not charging the battery i'd expect this, but do i need the light if i have a visual on the volt meter anyway?
  
  
  
• I also have an inline resistor, do i need this anywhere on this route? ( i'll use a standard 12v interior light bulb if i can )
  
  
• According to the haynes wiring diagram, if i use the resistor directly after the alternator, then it also feeds the fuel shut off valve in the Injection pump, is this needed or can the the fuel shut off valve receive standard 12v from the starter/battery?

If anyone can help with the above points, i'd be most grateful.

b+ terminal has brown wire/s to starter as is just nearest suitable connection,d+ wire goes to ingnition battery light in dash light has feed through diode ,w wire is feed for rev counter so not needed,you need the light to feed alt ,stop solenoid is direct wire from ignition to solenoid,all feeds come from starter to ignition etc

So i'm on the right road then, the d+ wire ( the thinner of the 3 ) goes to the charge/ignition light then onto the ignition. I don't understand the diode, i thought it was a resistor??

Where does this go, before the light and directly from the alternator?

Alternator ( d+ cable ) > Resistor > Charge/ignition light > ignition

Is that correct?

Jamesmartin is right here - for the alternator to charge it needs current to pass through its field coil which creates the required magnetic field. When you switch the ignition on, current passes from the 12v feed on the ignition switch, through the charge light and down to ground via the field coil. This gives sufficient magnetism for the alternator to begin generating current when the engine starts. Once the alternator is charging, the field current is provided internally through the field diodes and you end up with 12 volts (14.4v really) on both sides of the charge light so it goes out.

To answer one of the earlier questions - yes, you do need the light connected in order to "kick start" the alternator into charging and the voltmeter is useful to tell you what is actually happening to the battery. I'm not sure what the diode/resistor might be for - are you sure it isn't a capacitor for suppression? A picture might help here.

Cheers, Peter.

Sorry, just re-read the last bit of the original post - I wonder if the resistor is just there to limit the current in the fuel shut off valve? If it is shown in the diagram and things work with it in, I would leave it there. I wouldn't have expected it to be in line with the charge light though as you wouldn't want to limit the initial field current

ive wired a few from scratch and never used a diode resistor thingy.... cant see any reason for needing one.

your volt meter should read about 12 volt with the engine not running and about 14.5 volt when the engine is running

Thank you Ntfs & Ricc ( and JM ofc )

I believe the resistor was inline to the original dash panel lighting as well as other areas, but i also think i was looking at the diagram from the wrong direction now you have pointed it out.

If you reverse what you said, that's what i was getting, ie the resistor is last in the line ( why i do not know, i'm looking at the haynes manual :lol: )

Finally i can sort it, it's a simple job

Cheers

Finalising the wiring now, all temp connectors are being replaced with soldered & shrink wrapped finish to the connections and i shall place a charge light on the alternator cable.

Can i use a standard interior bulb for this? The defender set up is a bulb amongst a intricate set up on the dash panel, but using a series dash i just want a single bulb.

Do i earth one leg of the bulb or run the bulb with each leg on the wire, ie from the ignition to one leg and the other leg onto the alternator?

Ta

the bulb feeds volts from ignition switch to alternator to start it charging so one side goes to ignition on and other to alternator little terminal...

Thank you ricc