Weird Electrical Effect

[JTaylor2005]

Hi guys
My car runs okay and drives fine. Its just got another niggly little fault.

I just started it then and with the interior light on I noticed it flickering.  It was going up and down in brightness. Nothing else was on in the car like lights, or radio.
Also when I change gears and the revs drop suddenly I have noticed that the headlights dim quite badly and if the interior light is on at the same time it dims badly as well.

Do you reckon this could be a failing alternator or some sort of earth or wiring issue? I have cleaned up the earths that I could find when I got the car just over a year ago.

Thanks

[bashbarnard]

could be alternator or battery. even if it starts ok. check the voltage output of the alternator should be some where around 13.8v and i would also suggest getting your battery load tested by someone just to check it. there are a few tests to do on battries but thats one of them. failing that they are both ok then it could be a connection issue although i do think headlights and interior lights share a different earth but dont quote me on that

[JTaylor2005]

I know there is an interior earth somewhere in the underside of the glovebox I think it was. The headlight ones are just in front of each of the suspension struts.

I will measure the alternator output tomorrow some time and then see if I could get a battery test done. I don't know how old the battery is as it was the one that was on the car when I bought it. Its proper dirty though so could be really old tbf.

Probably doesn't help that I have two amplifiers capable of drawing near enough 80A haha. I will disconnect the amplifier circuit and drive it for a bit and just see if it has any effect.

[JTaylor2005]

I am going to do the big 3 wiring upgrade tomorrow based on a guide I have found on here. It was for a 1.9 but I'm sure I can make it work for the 2.0. It might make a bit of difference but it will help with the amps I have as well

[Toms306]

I 'think' there's an earth for the interior light on the roof above the console but it's been a while since I removed one now. There is one either side near where the door loom enters the car but that seems a fair way from the light tbh. 306 battery terminals are terrible so maybe worth checking those or even uprating them. The neg ones often don't tighten properly onto small terminal posts.

Also I'm pretty sure all lights dim if you clutch it from high rpm, the regulator can't smooth it that perfectly!

[JTaylor2005]

Yeah tbh I was thinking that the terminals were rather crap on these. Quick release seems pretty pointless on something you probably only take off maybe once a year haha.

[Niall]

Sounds to me like the start of a failing voltage regulator.
Get a meter on the battery when the car is running and rev it. Monitor the voltage. If it picks up, new voltage reg or alternator time

[JTaylor2005]

Does sound possible. Something like this would do then?
http://www.ebay.co.uk/itm/BOSCH-ALTERNAT...SwDNdVicbp

Would it be easy enough to change on its own do you reckon or would it be hard to get at without removing the alternator etc?

Thanks

[Poodle]

As Niall says, if your headlights are dimming as well that's a pretty strong indication of tired alternator. Do check your earths first though, and the battery terminals.

[Paul_13]

Give the alternator a sharp whack

[andywhy]

This used to happen on my Passat and it turned out that it was the aux tensioner being loose. After replacement it's not done it since. I do know some cars have electronic control of a lot of electrical loads so it sometimes pulses them when on the limit to stop the voltage going low and your battery draining. Though the 306 might be a bit old for that. My Passat certainly does it.

[Dreijers]

As, I can speak from my own experience, then this might be voltage regulator failing.
Symptoms of my car - 
1) power draw around 2A, when alternator disconnected - 0,05A (noticeably less)
2) When started car, Voltmeter on battery showed 18V, turned off car immediately. 
3) Completely all lights were dimming and brightening up.

Easiest way to get to voltage regulator is from the top, after lifting out of the way coolant reservoir.
And by the look of that voltage regulator, seems like a correct one, atleast that was on my car.
   
   
Take off that reservoir and bracket on which it is supported and after that you have to take off plastic cover on top of alternator, and after that just undo all screws which are on the end of alternator, swap voltage regulators and screw everything back together. 
To make things easier, you can undo oil filter, but be warned with consequences (oil on the ground etc.). 
When I did this to my car, I put back on old filter after voltage regulator swap, but soon afterwards I serviced it.

[JTaylor2005]

Brilliant info mate. Thanks for that nice one

[Dreijers]

but for me all lights were dimming and brightening up! Even my low beam lights were done after that, but everything else survived 18V!

[JTaylor2005]

Today I added a nice big cable from the alternator to the + on the battery. Although it hasn't really helped with this issue as such the engine turns over much faster when I turn the key and fires up quicker as well So overall that was a positive for £5.50 haha

[JTaylor2005]

Just been out in the car in the dark and the lights are so bright as well. It's like rainy dark weather and I can see loads haha