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Alternator not charging no 12v at small purple wire
Hi all,

We have just fitted a new alternator to my son's 2005 2.0 HDi and it is not charging as we are only getting 10.5v at the battery with the engine running.

I have read of a similar issue on a Peugeot forum and that there should be 12v at the small purple/violet wire when the ignition is switched on but there is no power there and unfortunately the thread tails off with no conclusion.

If I connect a 12v feed directly from the battery to where the small wire plugs into the alternator with the engine running we get a healthy 14.5v at the battery.

On the basis of the above I have assumed that the battery and new alternator are ok but there must be a problem with a fuse, relay or wiring feeding the switched circuit to the purple wire.

Can anyone suggest a solution as we have tested all the fuses in the engine compartment and inside.

Many thanks in advance for any suggestions.

Kind Regards

The alternator needs 12v to make it work.
This is usually supplied through the ignition switch. Faulty ignition switch ?
[-] The following 1 user says Thank You to brodfather11 for this post:
  • td5
Hi, This "excitation voltage" is produced from the Bsi and connects to the alternator through the engine bay fuse box.
Check all engine bay fuse connections and also the Bsi connections.
"EP" connector especially. You are looking for water damage from the windscreen leaking etc or corroded connections.
(The Bsi is the fuse box under the steering wheel).
2006 2.0hdi 600 with bench seat.  Cool
[-] The following 1 user says Thank You to Rustscrat for this post:
  • td5
Thank you both for the above suggestions and I can now confirm that the problem has been resolved.

It turned out that the new alternator I purchased was indeed faulty even though it appeared to charge correctly when supplied with a 12v feed directly. The explanation I was given was that on startup the alternator sends a pulse to the BSI which in turn supplies a 12v feed back to the alternator down the purple wire. No pulse was being sent so no feed was provided.

The alternator I purchased was an RTX make supplied by EuroCarParts whom I have been quite happy with in the past however when subsequently googling RTX alternators there do seem to be some mixed opinions/experiences from people.

So in hindsight my £90 alternator ended up costing me a further £330 (Another new 'decent quality' alternator plus second lot of labour to run diagnosis and swap units out)

Hope this helps anyone else in the same predicament.


[-] The following 4 users say Thank You to td5 for this post:
  • Husqyman, Ol'Jeffers, ron, Rustscrat

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