battery warning light

[scatman]

so i've recently replaced the alternator on my mk2 rocco. and now the battery light keeps coming on. there have been no adverse symptoms and its been like this for a few weeks and the car hasnt died or failed to start in that time.

conditions and symptons

light dims with higher revs. (this makes sense to me, high rpm mean higher voltage created)
light doesnt always come on (lose connection somewhere in the circuit?)
light goes off/become very dim when lights are turned on ( this one makes no sense to me)

so basically, what should i check? should i be concered about the car die-ing on me in the most inconvient time? (such as up hill on the motorway with a lorry right behind me, again)

[unknownmale]

Symptoms are a bit confusing.

Why did you replace the alternator? Are you sure it was faulty?
Have you checked the condition of the battery?
When installing the new alternator, did you clean the mounting point as this is the ground.
Made sure the two connections to the back of the alternator are secure?
Made sure the correct amperage alternator was installed.
Do you have any aftermarket accessories which draw excessive current?

[unknownmale]

Also, Make sure the belt is correctly tightened.

[scatman]

Altenator was the fault as I Brought a brand new battery for it and that didn't fix the issue.earth's are clean and,only a after market cd player which was fine on the old alternator. The amperage could be the issue, where can I find out which code new one is? So I could compare it to the old one.

[unknownmale]

Should be on the opposite end to the pulley (Where the two connectors are bolted in) anything 55amps + should be fine. If you have a multimeter you can check a few connections for voltage drops and and resistance. First worth checking would be positive battery terminal to the alternator case, battery voltage with the engine running.

[mark1gls]

Check the blue wire running from the alternator it runs along the front of the car and there may be a connection near the passengers side headlight (That where it is on my Mk1 Golf) the blue wire switches the alternator on so check the connections are clean as they do get rather grubby that near to the front of the car.

[mark1gls]

A bit more info.
http://vwgolfmk1.org.uk/forum/index.php ... st_1179326

[scatman]

thank you all for your advice (sorry im a bit late responding). the alternator should be 90amps, well it says 90A on it so im assuming thats the amperage. the blue wire is working as when the wire is connected the voltage over the battery is 13.5v ish and with the wire disconnected its 12.4v ish. however i had to connect the old one wire to new wire on the new alternator (hoop connector at the (old) alternator end is stuck to due to the fact the bolt it keeps spinning). could the connection be causing an issue?