chris wrx 95

iTrader: (1)

My battery goes flat far to quickly.
If I have the stereo on for 5 mins I cant start it.

How can I check if it’s the battery that’s dead or if the alternator has gone and not charging it properly. Or could it be both.

The battery is around 4 1/2 years old and the alternator is the Original one.

stonejedi

iTrader: (51)

hi mate i had that same problem on my wife's classic it cost me a brand new battery which went flat before i got a reconditioned alternator which has been on the car for 2 years and guess what no more flat battereys 9 times out of ten if it is not the batterey it is the alternator i hope this helps.

NUTTYNICK

You'll need a multimeter I'm afraid.
With the engine running, you should see 14volts (ish) at the battery terminals. Ensure you probe the battery terminals and not the cars electrical connections, this way you ensure a good connection between battery stud and cable.

If you get this then the alternator is good but the battery maybe shot. Check the fluid level if you can, it may need topping up. Boiled water is a good substitute to distilled water. I've managed to save a battery from the scrappy by topping up the fluid and cleaning the battery terminal/cable connections with emery cloth before.
The recent cold weather shows up weak batteries. Saying that, mine is brand new, was left for two weeks and was flat as a pancake. Not sure what is drawing power, but something is at a slow rate.

Hope that helps

Turbotits

iTrader: (2)

If you boost start the car and leave it running a while and this charges the battery enough to re start it again then its probably fair to asume the alternator is charging. Athough use of a multi metre as above would be the best option.

What you describe is fairly typical of a duff battery

mikey30

battery is worn out mate!!!!!
altenator is not the problem!!!!

chris wrx 95

iTrader: (1)

I should a mentioned before. My commander for the PFC says 13.9v most of the time sometimes sits about 13.2v and has gone as low as 12v.

It went flat the other day just from the door being open. The interior light was off and the only thing using power was the little red light on the dash to say the door was open. I Jump started the car drove it about for about 40 minutes and in the morning it was flat again. Jumped it again to pop down the shop which is about 5 minutes away and it was fine for the rest of the day. WEIRD.
The water level in the bat is fine and ive cleaned all the terminals but still no luck.
Don’t want to spend £70+ to get a new bat when it might be the alternator which I can get for about £40.

Multimeter reads 12v when the engine is off and 14v when running..

Turbotits

iTrader: (2)

put a multi metre on the battery and crank the engine and check the cranking voltage. From a static voltage of minimum 12.2 volts you should be able to to crank for 15 seconds without the voltage going below 9. if it goes below 9volts at all the battery is scrap

chris wrx 95

iTrader: (1)

It drops to around 10v straight away.

How do you no it’s the battery that’s dead and its not because the alternator isn’t charging it properly. Just want to be 100% sure of what it is before buying anything.

joz8968

iTrader: (13)

Why not put a mutimeter across output terminal on the top of the alternator (under the protective rubber boot)? I was at Zen's on Friday and saw Paul attending to someone's 22B-STi with alt/batt issues, and noticed him checking the alt. Thing is, I don't know what the output voltage should be ... Someone will be along soon, to say so, hopefully.

scoobian

go to a Kwik Fit or similar and get a battery check (they put a load across the terminals and it gives a better idea than the multimeter)

chris wrx 95

iTrader: (1)

I’ve put it on the alternator and it says 14v don’t know what its meant to be though.
Thing is the PFC commander says different voltages on different days but im not sure if its reading the battery voltage or the alternator. I’m going to go to kwik fit later today and see what they say.

rob 666

iTrader: (1)

sounds like a duff cell in the battery to me(4 1/2 years is a fair life for a battery)

joz8968

iTrader: (13)

The PFC reads battery voltage (not alternator).

NUTTYNICK

From everything you've said, your alternator is fine, 14volts is perfect. It will drop to 12volts as the charge in the battery increases. Trouble is, the battery is not storing enough oomph. The battery is **** as already said.

You need a new one, simple as.

chris wrx 95

iTrader: (1)

Thanks for all your help guys.

Just wanted to make sure it was defiantly the battery. Just order one and should be here tomorrow .
Once again thanks a lot.


Oh by the way Turbotits your scooby looks sweet. Love the all black look.