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benniferj

Member Since: 20 Oct 2016
Location: Basingstoke
Posts: 361

Alternator exciter wire

Hey guys. Ive got what was originally a 2.5.td 90 which has what can only be described as a pretty poor condition loom + it has been damaged during an engine swap from a botched Disco 200 conversion to a proper 200tdi Def engine.

Most is all good. Had some issues with power to fuel solenoid which I have worked around (for now)
At the moment alternator isn't charging. I have connected the exciter wire to the correct terminal but it doesn't work and I believe the 2 problems are related.

Rather than trying to solve that, which *should* be cured with a new section of loom that I have... Can someone explain the simplest way to get the alt charging without killing it swiftly too. As I understand the exciter feed has to have a 12v feed sent to it to activate. But is this momentary, it seems more complex as it is linked to the switch which then goes out because the feed goes 12v rather than ground or something?

I am running a voltmeter in the vehicle so can tell when it kicks in.

Please help!

1st Aug 2018 7:52am

dorsetsmith

Member Since: 30 Oct 2011
Location: South West
Posts: 4554

2 problems are related. see diagram below

Click image to enlarge

alt exciter brown yellow wire

fuel shut-off sol white wire

Last edited by dorsetsmith on 1st Aug 2018 11:41am. Edited 1 time in total

1st Aug 2018 8:39am

Martin
Site Admin

Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6613

2015 Defender 90 Puma 2.2 XS CSW Montalcino Red

Try this, clipped from the 300 Tdi diagram but it's the same basic system on everything before the Td5.

The resistor is to ensure the alternator is excited even if the bulb blows.

Click image to enlarge

Edit: basically 12V ignition -> battery warning bulb, other side of bulb -> diode anode, diode cathode -> alternator D+ terminal.

If you don't have the diode you can ditch it for testing, it's not in the TD wiring. So other side of bulb -> D+ terminal.

The fuel shut off solenoid is wired to an ignition feed (white wire).

1988 90 Td5 NAS soft top

2015 D90 XS SW

Last edited by Martin on 8th Aug 2018 8:30am. Edited 1 time in total

1st Aug 2018 10:45am

benniferj

Member Since: 20 Oct 2016
Location: Basingstoke
Posts: 361

Got to the bottom of it. The problem with the fuel pump solenoid was a faulty bit of loom. This got fixed when I replaced the whole loom as a precaution!

The alternator issue... was driving me nuts. Put the alt that came with the donor engine back on and it worked perfectly. Brand new Bearmach alt dead new out of the box! Thanks for the diagrams, gave me a bit more confidence that it wasn't my fault it wasn't working!

8th Aug 2018 8:29am

Martin
Site Admin

Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6613

Glad you got to the bottom of it

1988 90 Td5 NAS soft top

2015 D90 XS SW

8th Aug 2018 10:21am

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