bust altenator?

[anth_dci]

This is for my bothers 1.2 clio, i know its not a megane but the same princple applies so im hoping someone can confirm my diagnosis of bust altenator.

Symptoms:
car wont start without a jump, wont even turn over, no lights no fans etc,

when driving if you turn the lights on it dies

put a multimeter over the terminals, didnt get any reading at all, but this could be because its a cheap old one so that might be at fault.

opinions appriciated

[AlexB]

Replace the battery. As it drives after jump, the alternator is good.

[anth_dci]

forgot to mention, it had a new battery in december. with it cutting out as soon as u turn the lights on leads me to the alt?

[AlexB]

No, usually this leads to the battery. I the alternator is dead, the car would die immediately after disconnecting the jump leads.

Bad contacts can also cause cutting out when light are switched on, but then the lights would be operational in the mornings.

[davelowe]

I'm tending to agree. The battery may well be to blame. However, it's odd for a new battery to fail so soon.

Alternators do not work well without a load. I would look at the connections between the two and earths. It's possible that there is an alternator fault which has lead to premature battery death (by discharge), but I very much doubt it.

If possible get an accurate battery voltage reading when cold, and a reading when the car is running. This should help with the diagnosis.

[AlexB]

Dave,

The battery was discharged to zero every night since some time in December, assume 20 times. It might be dead by now anyway. Furthermore, Clio owners tend to find very unusual makes of batteries, which are not Bosch or Varta.

Voltage readings show three things: if the battery is charged or not, if the battery has a shortened cell and if the alternator is charging. Batteries that have lost their capacity charge quicker!

anth_dci,

I agree with Dave, check the voltage directly on the battery when the engine is not running. Do it with and without lights. It can be a resistive contact somewhere. I hope, the battery terminals are clean and covered with lithium grease. Check if all wires are connected to the positive terminal and the large fuse is OK.

[davelowe]

The battery was discharged to zero every night since some time in December, assume 20 times. It might be dead by now anyway.

I can't argue that discharging the battery to zero won't knacker it. Once is probably enough, never mind 20 times. However, this isn't explicitly stated as being the case. The question also remains, why was the new battery discharged every night (assuming it was)? Something drawing power that shouldn't be?

[AlexB]

True. The original poster, unfortunately, chose not to tell us everything, e.g. the car model and how this problem started. I any case, the solution will involve a new battery of a good make and checking the system for the circuits that drain the current when parked.

[anth_dci]

fixed it, thanks for the advice. Turned out it was the earth between the battery and the body work was badly corroded, cleaned it up and the cars now fine