drove to work last night and parked the car up, everything fine, jumps in to come home and flat battery, boosted battery off and let tick over for 15 mins.
i then proceeded to drive home, as i was driving my dash lights and external lights just became dimmer and dimmer, eventually i had to turn my lights off and the fuel pump was loosing power, thought i was going to have to leave the car half a mile from home but managed to coast it here.
what do people think, alternator or battery.
cheers in advance craig

 

sound like your alternator but i say your battery be on it way out to you can get a battery and alternator tester to see what ur charge is

 

cheers, going to go out in a min to see if it actually starts again.

 

Alternator or wiring is toast.

You can drive on the alternator alone if need be, as long as you do not get close to the rated amperage on the alternator (wouldn't run more than 50A on a 90A alternator for example).

If you are losing power when everything is turned off, then the alternator cannot produce enough power to replenish.

Would charge the battery up overnight, start the car and have the headlamps on, then check the alternator output @ the alternator terminal itself, then @ the battery and see what the difference is. IF it is around 14V @ the alternator, but around 12-13V @ the battery
then the battery lead is breaking down. If the output is low@ the alternator, then that is the problem.

You need to do it with the headlamps on really as this removes the surface charge from the battery to help prevent a false reading, plus makes sure that the diode packs on the alternator have kicked in sufficiently for an accurate test.

An even better way would be to use an ammeter inline to check more accurately, but as most people do not have ammeters rated to 90A+, the method above will be suitable enough.

 

sounds like the same problem as i had once, sounds very much like the alternator has either died or your earth strap has become disconnected some how and no charge is getting to your battery thats why everything slowly went off check all the wiring and if thats ok then new alternator i'm afraid.
Could be a good idea to get a new battery at the same as they don't like being completely flatened too often.

 

Some batteries are it seems better than others about being flat, as when I had bodywork done on my car the people left it flat for 3 months(despite the agreement to keep it charged), I expected a bit of a dodgy battery but mine is left two weeks sometimes and starts up perfect does not seem to have had any effect on the 7 year old battery.
Other batteries I had lasted just 3 years sometimes!!
tabetha

 

put a voltmeter across the battery terminals with the engine off
then start it up and do the test again
and get someone to do a drop test on the battery as well
post up the readings

 

deffinatly the alternator that is i had that problem on a cavalier i had

 

getting alternator today, started car yesterday and let it tick over then put voltmeter on, charge was slowly coming out so alternator must have seen its day. put lights on and stereo and charge dropped dramatically.
thanks for all the help guys, much apreciated.