what is the battery voltage meant to be on idle? mines reading at 12.5 then hits 14 when the revs get to 3000 is this right? i though it was meant to be 14 whenever the engine was running
cheers

 

new alternator time!

Your right it should read 13-14 volts all the time, depending on how much the battery is being charged

Alex

 

If it's only only initial start up that charges at 12.5 then charges at 14v after hitting 3k it is fine as you not hitting the fast idle setting in alternator but if it charges at 12.5 after the intial revving then new alternator/regulator time.

 

If it works after you rev the engine to 3k then the field windings are not being powered by the "car". Thats the purpose of the dash warning light

Alex

 

So following on from wot alex says above is battery light working on dash as this must complete a circuit for alternator to charge properly.I think this is right alex.?????

 

Yes


The warning light exists as an easy way to power the field coils so the alternator will charge from very very low revs.

When you spin the alternator fast enough it will "self energise".

So when the alternator is functioning correctly it outputs a voltage from the field coils that matches the voltage trying to be fed to the alternator. This means that electricty won't flow and the light goes out.

Some cars alternator seem to fail but its just the bulb thats gone


Alex

 

As above.

 

if ya belt is loose/slack can that cause the same?

 

ok so ill check my battery light as when driving normally below 3k it does seem to run rough as if its not gettin enoughpower for a good spark and if i have a lot of electrics on then it does just die and wont start again.