As above had a bit of a problem recently and its to do with my alternator or battery or something

Basically the cars had a new battery about 3 months ago so i think i can rule this out

Now what does the little blue wire on the alternator do ? something to with batt light ?

Went to my alernator tonight and re-done my connections and also this blue wire connection ? , i moved it to another bolt on alternator ? now my batt light stays on ? easy changed back i suppose

Now previos to this with my car running i was getting 11.36v on the batt terminals , now after redoing my connections and cleaning some stuff up , i jump started car and now on batt terminals with car running im getting 13.56v ? and switched off about 12.67v ? dunno i fixed my problem ? but are these readings about right and also would i need to change this wire over to get light to go off ?

any help appreciated as its like pissing in the wind with probbs like this ?

 

HI,
The blue wire is the FIELD EXCITATION WIRE, this as you have discovered goes onto the terminl at the back of the alternator.
The wire is from the battery(ignition) warning light when ignition is turned on a 12 volt LIVE FEED goes through the bulb down this wire and to the alternator exciting the field windings to start producing current(volts) when engine is running.
Of course if your bulb blows you have no charging, but you can briefly touch 12 live onto terminal to start charge once engine is running.
With lights, heater, hrs on you should be looking at around 13.4-13.8 at 2000rpm.
tabetha

 

Thanks , good info there , need to take it a run to see if iv fixed it , strange hing is all voltages seemed great last night , but didnt take it a run , just sat idling for 15 mins , this morning i went out and battery had went from 12.7 volts at night with no engine running , to 11.4 volts and obviously couldnt start car what would cause this ? ive got a ugly night rider type alarm light that ws on the car whem i bought it , basically is a red light that moves form left to right constantly , could this run my batt down just a idea

 

It should have no problem starting at 11.4 volts, as when starter turning will drag it down to 8/9 volts anyway.
It does sound like you battery may be a little tired, get it RAPID DISCHARGE TESTED to see.
The alarm will certainly sap power, but should not be enough to prevent starting overnight unless battery u/s.
15 minutes idling will not put back in what you took out for starting car, it needs a good run or charge overnight.
tabetha

 

Thanks for that , off tomorow so fingers crossed iL get it sorted