Alternator replaced but battery light warning now showing

[mij786]

Hi,

Over the weekend, my car cut off mid driving, power had gone, and was unable to re Start my car. The garage recovered and managed to jump start it but he did some diagnostics and said the alternator had gone. The voltmeter was showing around 11.4, apparently a minimum 14 was required. He replaced the alternator with a used one from a seat alhambra but the problem is now when I turn the engine on, the battery warning indicator comes on - however, if I rev the engine above 3000rpm the light goes off and doesnt come back on again unless I start the engine again.

Is this a shoddy job / incompatible part replacement? What does it effectively mean in terms of the battery getting charged? Is it likely to fail? Thanks for your help.

 

[WeeC]

Sorry I can't help (not a technical boffin myself) but I will be interested to know the outcome as I suffered the exact same problem on Friday night with my Ibiza! Now waiting on a new alternator to arrive so I can replace it.

From my quick check on ECP, the alternators coming up for both Ibiza and Alhambra are same part numbers and other details.

 

[Slimy]

Have you checked the voltage on the new one?

The most obvious cause would be a dodgy earth strap, either broken or not connected on one end.

 

[mij786]

The voltage on the new alternator was showing was around 12.5 which isn't sufficient from what I gatherered in the last few days.. I have ordered a used alternator from eBay which matches the exact part number..hopefully that should resolve it..I suspect the one currently fitted is a 12V but the model I require is 14v..I will update in due course..thanks

 

[lar]

if you rev the engine and it battery goes out and stays out even when the engine returns to idle theres nothing to worry about. as long as the light is out the battery is charging, this is normal on a lot of cars. If the light flickers at low reves check the tension in the belt

 

[mij786]

I got the alternator replaced yesterday with exact part I purchased from eBay. This seems to have solved the problem, no warning lights, and the voltmeter showing around 14.5 while engine running.

 

[carp]

Maybe where your alternator went you need a new battery too - mine went not too long ago and bled the battery of all it's life and so both had to be replaced. Or maybe I was just unlucky haha

 

[WeeC]

I now have battery/alternator problem again! Fitted new alternator and belt, new battery and it has been fine for a couple of months. Thursday night however, battery light flashed and then a little later the lights dimmed, dash lights came on and a few minutes later (after much coughing and spluttering) engine died and battery flat. I am thinking it's now a case of the alternator not charging the battery through faulty wiring. Does anyone have a wiring diagram/info on relevant connections between battery and alternator and any other ideas what the problem might be?

(edit - I have a mk3 1.8T 6K engine code. The mk2 in my sig sadly has gone)