VW Electrics alternator checking

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Alternator dash light staying on


Disconect blue wire from back of alternator, dash light should go out, if it stays on there is a short somewhere between alternator and the the dash light.


First up check the connections from battery to Van. Terminals should be bright shiny metal not green or black. Rub em down, clamp up connectors (not over tight) cover em in vassaline. Have a look at the engine earths while you are at it.

Charge the battery overnight. Check battery voltage with engine off (12V ish) If reading low battery buggered. Check battery voltage engine running (14.5V ish) If low alternator not charging propperly or battery taking too much currant.

With engine OFF Remove +ve lead from battery Connect one lead of a test lamp or an ammeter to the battery +ve connect the other lead to the van battery connector. Does the lamp light or the meter read a currant if so something is draining your battery.

Keeping the battery warm will increase the power it can deliver. I'd be wary of keepin it covered as you might trap explosive gasses or accidentaly short out the terminals.

Spoke to a guy yesterday and he said that if I removed the blue wire and earthed it, and the red battery light comes on its an alternator fault, he said that if I earthed the blue wire and didnt get a light it was a bulb/wiring fault...?

Charge your battery overnight and test again. 12-13V with engine running is a pretty good indicator that the alternator is not putting out charge. have a look at the back of the alternator and remove the black brush pack. If the brushes are short ie less than 7mm buy a new pack and see if that helps.

If the brushes are OK you are looking at a new alternator.