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Model specific boards => Golf mk3 => Topic started by: Dan_GTi8v on 18 May 2011, 19:32

Title: How to test alternator?
Post by: Dan_GTi8v on 18 May 2011, 19:32

My battery warning light is on all the time with engine running, thought it was alternator so changed it but its still on :( How can I test the alternator to check I havnt bought a duff one? Also what else could I check?

Cheers

Title: Re: How to test alternator?
Post by: dom on 18 May 2011, 19:35

Whack a multimeter on the battery with the engine/all electrics off and it should read around 12v, start the engine and if the alternator is ok the reading should go up to about 14v. If it doesn't then the alternator is more than likely at fault :wink:

Title: Re: How to test alternator?
Post by: Dan_GTi8v on 18 May 2011, 19:46

Cheers :) I got a feeling its gonna be something else but would be good to rule out alternator. I'm guessing if it was a wiring fault this method wouldnt help me though?

Title: Re: How to test alternator?
Post by: nikkiy9 on 19 May 2011, 10:25

Could it not be a dodgy wire, had it before on an older car and it was just a snapped wire

Title: Re: How to test alternator?
Post by: boneybradley on 19 May 2011, 11:51

many car spares shops offer battery and alty testing and should use the correct machine... to test the wires is more conplicated and needs a multimeter accross the plug

Title: Re: How to test alternator?
Post by: trog_nfs on 19 May 2011, 11:54

If there's a Halfords near you I know they can do alternator tests. I used to do them after all  :grin:

Title: Re: How to test alternator?
Post by: Dan_GTi8v on 19 May 2011, 13:38

I know the positive wire works as the light comes on if you ground it with a screw driver or something (think thats right) other wire just goes to the ecu I think? I may be able to get a multimeter on it tonight, is there a way to test the alternator itself without using the battery so I can rule out wiring or whatever?