Golf Mk2 GTI - Alternator issue?

[IceBoy]

Hi All,

I've had the mk2 GTI 8v on the r oad for 6 weeks now, having been sorn for nearly 5 years.

Slowly, slowly things are going wrong, but I knew this was going to happen.

First it was the fuel pump, which is now sorted....etc.

Anyway, fast-forward to yesterday....I was driving the car and the alternator LED light on the dash was on but very dim. Today I noticed that the light was changing from dim to bright!

The light does go off if I rev the engine but then comes back on after 30 sec or so.

The belt seems fine and is tight.

Is the alternator on the way out?

Help
IceBoy

[kambites]

Probably the voltage regulator rather than the alternator itself. It's probably built into the same physical unit but is sometimes replaceable separately.

Stick a voltmeter across it to see what you're getting at different engine speeds. If the regulator is working properly, you should get a flat 14ish volts all the time; if it's not the voltage will vary with engine speed.

[Riknos]

Voltmeter on the battery too, both when the car is on and off, to see if the alternator is charging, could be a shagged battery, or earth points. 5 years some earths could have rusted off.

Is it a new battery?

[StottyZr]

I had the exact same problem on my 106 Gti the other week (battery light dim, brightening and going off when revved). It was the alternator, I checked with voltmeter and the alternator was way down on what it should be pushing out. I don't know the ins and outs on how they work so I just bought a replacement from a forum member. All well now

[aka_kerrly]

Check the blue wire that runs from the alternator which intersects the live wire from the positive battery terminal. The plastic connector leaks which causes the copper connectors to go green/furry = bad connection.

If you can get a multimeter and measure the voltage across the battery terminals with the engine running you should have over 13v minimum if you have a semi healthy alternator, it ought to be 14+ to keep the electrical system running happy.

As soon as the voltage drops under 12v then the alternator is kicked in, I think I'm right in saying that the clocks send 12v to the alternator via the blue wire which if 12v don't come back then the light on the dash is displayed.

[gfunk]

Had the same on my mk2 it was the alternator.
Got one from breakers and swapped in about 15mins so not a major problem.

[crofty1984]

Had trouble with my alternator on a mk2 polo. It was leaking oil a bit out of a breather, which was getting in the alternator and turned the bushes to mush. Put new bushes in and all was well.

[steveo3002]

voltage regulator and brushes are in a little unit thats around £10. 2x phillips screws to swap it , often restores them to full power

[IceBoy]

The battery is new, so I will check with a volt meter and see what my findings are.

The strange thing is that it is LED intermitent. From very dim to bright and not at all?

IceBoy

[IceBoy]

Just a quick update for those those that might be interested.

I did not have a multi-meter to test the voltage but spent and hour on:

All earth points - cleaned and wd40
All wires checked - wd40
Took off the regulator (pain to get too) cleaned out and wd40 on all bits
Checked the alternator belt - ok

I then put it all back together and went for a 10 mile Italian tune up......no more battery LED...fingers crossed.

I will be driving it later and will check once again!!

Looks like it could have just been bad contacts/earths.

IceBoy

[aka_kerrly]

IceBoy said:

Looks like it could have just been bad contacts/earths.

IceBoy

When you say you did all the earths did you clean up the main earth from the battery terminal to the chassis leg to the gearbox? This is by far the most important wire and if it goes even slightly green all sorts of bizarre electrical gremlins appear.