Hi there

My 2004 STI has a weird issue for me to diagnose.

It has a new battery, but i had to charge it after leaving a door open on thursday night.

So this morning with the battery fully charged( according to my charger) I went for a 20km drive. When I got home and while waiting for the gate to open, my battery light went on. I drove in and while waiting for the second gate to open it suddenly went off again when I engaged 1 st gear. I drove in and parked.

When I went out again later the battery light came on again after a a few minutes of driving, this time joined by the handbrake light. The handbrake light come on at about 75% strength, because when I do pull up the handbrake it shines brighter.

I parked the car for a while and disconnected the battery and re-connected it. The battery light came on again, right after starting it.

...So then I left car for a good long while......I started it and no lights came on.....but 45 seconds later the battery light joined by the dim handbrake light came on again.

I now have it parked and I'm sure if i leave it standing long enough ....the light won't be on upon starting it.....but it will come on after 5 mins of driving or maybe sooner.
If I start it right now, the battery light will be on from the get-go.

So it seems that the alternator stops working when it gets warm....or the battery runs out of juice after a while.

I checked all the fuses, they seem fine.

What the hell is going on here?

 

First make sure the belt is at the correct tension, and all the connections are good then with a multimeter on the battery with engine running you should see 13 to 14 volts with some electrical items on sutch as head lights/blower, if not you will need new alternator.

From what you have described this happens when hot, possible breakdown of the internals of the alternator.

 

thanks inviroman.

they did replace a bolt near the alternator. i asked him whther that is the right tension...he replied he doesnt like to pull too hard on an alternator!

i suspected this, this morning...but now that you have mentioned it out of your own...i bet a 100 pounds that , that is the problem.

I'll have him tighten the belt more tomorrow.... how much play should the belt have when cold?

 

sounds like loose belt,i had a similar issue
the belt should have about 1/2" to 1" of movement when tensioned

 

thanks Jake. This forum is awesome, or rather the people on it thanks guys!!!

 

I'm pretty sure the alternator only charges effectively if you run with sidelights/blowers on etc due to it being a smart charger, that's what I seem to remember being told lol.

I tension my belts using the twisting method.

Mick

 

no problem,hope you get it sorted
and yes i believe it dont start charging until a sufficient load is put on it,or something like that im not 100%
twisting method is also good

 

I had battery problems then read about battery not charging without a load on it. have driven the car with the lights on ever since without any problems. You have 2 gates !!!!

 

thanks again guys. will post tomorrow after re-tensioning is done. have a great week!

 

Smart type alternator maybe.

 

After going through all the motions, it turns out to be the voltage regulator....