2000 Polo GTI Battery Light Stays On

[BeirutTaxi]

Hi all,


I'm currently looking at a Polo GTI (2000). However a problem with the car is that the battery light stays on whilst driving and the battery drains over a few days. The car has a new battery.


I would be grateful if anyone could shed light on what the issue could be.

Many thanks,


Matt

[annodomini2]

1. Check the drive belt hasn't come off.
2. Check the wire is connected.
3. Change the alternator.

[MarshalRay]

Do a quick check - if you have a multimeter, measure the voltage accross the battery. With the engine off you will probably have something like 12.8v (depending on the current charge).
Start the engine and check again. You should now have something like 14v.
If you dont have this sort of increase in voltage, then it points to the alternator. (the drive belt slipping, damaged wiring from the alternator, the rectifier pack on the alternator or the alternator itself).

[illmonkey]

MarshalRay said:

Do a quick check - if you have a multimeter, measure the voltage accross the battery. With the engine off you will probably have something like 12.8v (depending on the current charge).
Start the engine and check again. You should now have something like 14v.
If you dont have this sort of increase in voltage, then it points to the alternator. (the drive belt slipping, damaged wiring from the alternator, the rectifier pack on the alternator or the alternator itself).

This. If its only 12.8v or similar, check the excite wire. Mine broke, and the fix was to run a new cable from the 12v + of the battery to the excite terminal. It tells the alternator the car is running, and therefore outputs 14V. Seems illogical, but it is an issue.

[BeirutTaxi]

Bit odd, I charged the battery up and took the car out.

After giving it a fair bit of revs and poke in second gear, the battery light went out.

I immediately got the multimeter out and with the engine running the voltage was 11.8V across the battery. The other day when I tested it with the engine running it was something like 11.2V

The belt doesn't appear to be slipping either, the belt drives the water pump and the engine doesn't overheat - which to me also shows that the drive belt is in correct working order.

Bit stuck as to what it could be - Thanks for all the replies and helps so far

Is there any way I can directly test the alternator?


Many thanks,

Matt

[annodomini2]

Should be reading about 14v with the engine running.

Alternator is not charging.

[stevieturbo]

BeirutTaxi said:

Is there any way I can directly test the alternator?


Many thanks,

Matt

You pretty much have already. If you arent seeing near 14v at the battery with engine running, then the alternator is not charging.

Weird that the light has went out though...although could just be a sign that the alternator is really buggered now lol

[BeirutTaxi]

What's the probability that it's a cable issue?

[99hjhm]

Alternators are dead common problem on those the Lupo/Polo GTI. Make sure you get the right one as they vary depending if you have AC or not.

[annodomini2]

BeirutTaxi said:

What's the probability that it's a cable issue?

Unless it's disconnected, low.

You can continuity check the connection from the alternator to the battery, with your multimeter, if you wish.