Alternators...what does that little wire do??

[chrispy.clio]

So i've been having some alternator / battery issues on my trackcar.

What does the very thin wire that goes to the alternator actually do?

Is it just to power the light on the dash or does it spike the Alternator into charging the battery?



Just to note i have custom made engine & Interior looms so no renault rubbish.

 

[bmh.01]

Its the exciter feed, off the top of my head on the Clio 2 its normal and nothing fancy like the later serial connections. Its needed for the alternator to work.

http://en.wikipedia.org/wiki/Alternator

Above link will explain why.

 

[chrispy.clio]

So does that wire just need to be linked to the battery positive?

 

[bmh.01]

Hmm i'm starting to think that they might be internally excited now as having just looked at the wiring diagrams it looks to be just the charge indicator feed. If you test between battery positive and the connection with the car stopped you should get battery voltage (which would put the battery light on), when running it should be 0v (which would extinguish it) or near enough as long as it picks up then i'd say you don't need it.

Whats the charging issue?

 

[chrispy.clio]

Oh right!

The car will start, but my volts display on my homemade dash says around 12v and as the car runs the volts drop off until the car dies after a few minutes of driving!

the only way I could drive was to bodge a Battery Booster pack onto the battery and do a 15minute session on track. I did two 15 min sessions on track and called it a day after that!

Now when I got home (car trailered everywhere) I noticed the alternator belt was a bit loose. Now when I tightened it up a lot then my fancy volt display started to say 13.5v and went up a tiny bit when I revved it.

The thing is the car is not road legal so I can't test it properly until my next track day in a few weeks time so I was wanting to get everything covered befor taking it to the track day so it's not a waisted journey!

so it sounds like I may not need the wire.