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Ph2 172 alternator exciter live with ignition off

Hi Folks,

My 2002 Ph2 172 started flattening its battery, some investigation later and there was a 4A drain over the alternator (measured between the alternator post and the large charging cable).

I fitted a used alternator, which seemed to be working at first, but got extremely hot and burned off all the varnish from the windings. Suspected internal shot which according to the alternator specialist I spoke to is a fairly typical failure mode on these.

I ordered a remanufactured alternator and fitted it and the car is charging fine. Checking for any drain, I have a 0.2A drain across the alternator and some poking around later, the smaller exciter wire is live even with the ignition off. if it's disconnected the drain on the battery goes away. I assume this is meant to be live only with the ignition on like every other car I've come accross?

I've had a poke at the wiring diagrams here: (Thanks @conor1n ) and the alternator wire seems to come directly from pin 11 on the instrument cluster with no detail of the internals of the cluster. I tried pulling the cluster fuses (2 and 21) and the voltage was still present, so perhaps the voltage is getting into the cable through damage or similar.

For now I have disconnected the wire and the alternator seems to self-excite okay but need to get to the bottom of it, has anyone seen anything similar before?

  172 Ph1
It’s not an exciter wire , it’s a wire that’s needed to control the Alternator / battery warning lamp .
The alternators that are self excited from within the unit only have 1 small wire in the black connector . If you have 2 small wires only then is one an exciter , normally the older Renault alternators were like that.

So getting to your issue :
pull the cluster out and see if the wires voltage goes away , if it is still present then proceed to check the wire for a short to live .
If the voltage goes away then it’s poss a cluster issue as that’s the end of the line.

So power is at the bulb , and the other side of the bulb should be earth when ignition on (alternator) not rotating .
Once idling 12v is produced from the alternator and the small wire becomes live and that then puts the warning light out .
Here’s a question ?
Does you warning light come on as normal ? , because if the small wire at the alternator was live then in theory that would put the warning light out.