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Model specific boards => Golf mk3 => Topic started by: Shady Pioneer on 07 January 2011, 12:43

Title: Testing battery and alternator
Post by: Shady Pioneer on 07 January 2011, 12:43
So my car died again 2 already this year. I had a new battery a little over a couple of months ago, and it seemed to work fine and do the trick, but as of the late it's been struggling to start. I've gone and got myself a tester, but where and how do I use it? Don't want to go killing myself.

I'm hoping it's the battery that's at fault as that can then be replaced for free, however if it's the alternator I don't want to be shelling out £70+ on a new one.

Any help?
Title: Re: Testing battery and alternator
Post by: LowlifeDubber on 07 January 2011, 13:16
Set your multimeter to 12v put it on the battery.You should get a reading of about 11.5-12.5v now leave the tester on and start the car up.
Now the voltage should go up to about 14.4v give or take.Much more and your alternator is overcharging.No move at all and it's not putting a charge in.
Title: Re: Testing battery and alternator
Post by: Shady Pioneer on 07 January 2011, 13:28
Thanks for the info bud. How would I know if the battery is at fault though?
Title: Re: Testing battery and alternator
Post by: LowlifeDubber on 07 January 2011, 13:43
With the engine off put your tester on the battery,now turn everything on,in the car.Lights,heater,wipers demister etc.Then watch to see how far it drops and how fast.

If it starts dropping pretty rapidly to the point where it goes under 10v then it's likely that its your battery.
I tend to drive down to the local tyre place(not kwik sh!t etc) and ask them to do a drop test on your battery,its a similar test,where they put a load on the battery and see how far it drops.
It's always free for the check in 99% of the places too. :cool:
Title: Re: Testing battery and alternator
Post by: Shady Pioneer on 07 January 2011, 13:48
Ace. Cheers bud. I'll try the tests this eve and see what I get as a result. Still hoping it's the battery. :grin:
Title: Re: Testing battery and alternator
Post by: VR6_Wherry on 07 January 2011, 13:57
It could be that something is on when you turn the car off.. Thus draining the battery overnight..
Title: Re: Testing battery and alternator
Post by: LowlifeDubber on 07 January 2011, 14:39
Id rather it be the alternator.Easy to change and a second hand one is cheaper than a good battery :grin:
Title: Re: Testing battery and alternator
Post by: Shady Pioneer on 07 January 2011, 14:46
Id rather it be the alternator.Easy to change and a second hand one is cheaper than a good battery :grin:

2 year warranty and it's only 2 months old. :evil:
Title: Re: Testing battery and alternator
Post by: LowlifeDubber on 07 January 2011, 15:28
Oooops,missed that :grin:

Yep lets hope your battery is shagged then :evil:
Title: Re: Testing battery and alternator
Post by: Bellend on 07 January 2011, 17:53
Sure it's not a starter?

If you get it checked out I have a spare 70A alternator. If it's correct ampage which it may not be I'll post it to you and you can try it out. If it sorts it it's yours.
Title: Re: Testing battery and alternator
Post by: Shady Pioneer on 07 January 2011, 19:55
Thanks Bellend. I used the tester and looks like the alternator is fine, it's charging correctly as results came back with 14v, howevermy battery was only 50% which for a new battery seems odd don't ya think? I'm going to take it somewhere tomorrow to get it tested properly, if all goes well I'll be getting a new battery.
Title: Re: Testing battery and alternator
Post by: Bellend on 07 January 2011, 20:38
No worries.

Have seen alternator diodes fail as they get warm though, so not fully charging battery.

Does sound like the battery though, which is a result. :afro: