Alternator Behaving Like A Dynamo

[KRISKARRERA 2 1 Cars]

When I start the engine and turn the headlights on they are not as bright as they should be. If I increase the revs to just below 3k they return to normal brightness and stay that way even if I allow the engine to return to idle speed.

It's been like this a few weeks now and I think it must be because of the time of year the car isn't ever being driven without the lights on. Also if I've got the fan on demisting the window and I operate an electric window switch the fan sounds like it's had most of it's power taken from it.

 

I'm thinking battery is past it's best, agree?

[Guest smokinslim]

Test the battery, see what sort of voltage its holding. Try a known good battery for comparison. Perhaps the bushes etc in the alternator are needing replacing if the battery's ok.

[RossD 43]

Either the battery or the regulator on the alternator, or as above the brushes!

[Anthony 1,000]

It's the alternator, or the thin wire has come unplugged (see if the battery light comes on with ignition on but engine off). My Passat had this issue for over 30000 miles and the alternator worked just fine, you just needed to remember to rev it to 3-4k once for it to start charging.

[McPikie 0]

It's the alternator, or the thin wire has come unplugged (see if the battery light comes on with ignition on but engine off). My Passat had this issue for over 30000 miles and the alternator worked just fine, you just needed to remember to rev it to 3-4k once for it to start charging.

 

I have the same sort of issue, although mine is more of a disco. The headlights, dashlights and interior light flash "lightly" when first started until warmed up

[KRISKARRERA 2 1 Cars]

Just did a few voltage tests.

Battery before starting: 12.3v

After starting engine: 11.7v (way to low obviously)

Turn headlights on: 11.4v (as above)

Rev to 3000 and let idle: 14.2v (which is correct)

 

Anthony, how does the small wire help the charge? I thought that is just there to tell the dash warning light when battery is low?

 

Could the belt be slipping? I don't reckon it is, they squeal when they do that.

[Anthony 1,000]

Anthony, how does the small wire help the charge? I thought that is just there to tell the dash warning light when battery is low?

 

Could the belt be slipping? I don't reckon it is, they squeal when they do that.

Definately not the belt slipping.

 

I don't know the exact workings of it (I'm sure someone else can explain better) but that wire has two functions - firstly it triggers the warning light if the alternator isn't charging (or it's meant to - in my experience it only seems to if the belt falls off), and secondly, it acts as a trigger/exciter (sp?) to make the alternator charge.

 

Without it connected, the alternator won't begin charging until you rev the engine (usually 3-4k) which spins the alternator fast enough that it self triggers/excites and begins charging and it will usually keep charging fine for the remainder of the journey

[KRISKARRERA 2 1 Cars]

Ah, thanks for that info Anthony, it'll be the connector then. It was a bit loose last time I looked at it.

[saveloy 8]

I doubt it's the wire bud. Sounds more like a very iffy battery. After a run check the voltage. You should see 12.7V. If you see less than 12.6V I'd say the battery is sick.

Do you like Scarlett Johansson?

[KRISKARRERA 2 1 Cars]

Easy to check that then. I'll nick the battery out of my dad's GTI6 tomorrow.

 

Yeah I've got 1233 pics of her in my hard drive's celebs folder which contains 33,209 images in total but why did you ask?

[saveloy 8]

Cos I'd love to make hot, sweet love to her botty.

Why do you ask?!

[KRISKARRERA 2 1 Cars]

But she might not like it up her cornhole!

[saveloy 8]

Oh don't say things like that Kris. I really had my heart set on it.

[KRISKARRERA 2 1 Cars]

Don't be crazy, your heart would never fit up there!

 

Anyway, I can't use my dad's GTI6 battery, he's worried about the hassle of the alarm or something. That only leaves my mum's Corsa battery. Actually I suppose I could always charge mine up overnight and see if there's any change, just to eliminate the battery from the proceedings. Battery must stay anyway, it's red and matches the rest of the bodywork.

 

I wonder if she's good with alternators?

[saveloy 8]

http://www.pughosting.co.uk/photopost/uplo...0/Scarlett2.jpg

 

Who the hell cares!

Edited November 25, 2007 by saveloy

[jim205GTI 3]

haha i think we need to start a seperate scarlett appreciation thread at this rate!!

[maxi 36 1 Cars]

I have the same sort of issue, although mine is more of a disco. The headlights, dashlights and interior light flash "lightly" when first started until warmed up

 

Bloody Northern showoff with your mobile night club! I think I might actually be jealous of a northern pikie......

 

Maxi

[benje 0]

IIRC Alternators need a *boost* as it were to start charging, something to do with energising the coils. It sounds to me like your alternator may be knackered.

 

Ben

[KRISKARRERA 2 1 Cars]

I'll have to put 5w40 in so I can rev to 3000rpm on start up without damaging the engine

[flipperthebushkangaroo 2]

IIRC Alternators need a *boost* as it were to start charging, something to do with energising the coils. It sounds to me like your alternator may be knackered.

 

Ben

 

Quite right, an alternator requires "exciting" the excitor wire doubles as the battery warning circuit, if this breaks you will not get a battert light when you switch ignition on and the alternator will not work properly. it routes through the dreaded brown multi plug above the gearbox.

 

Hope this helps

Roddie

[KRISKARRERA 2 1 Cars]

Does that apply to 16 valve too?

 

I wonder if my dad would notice if I swap engines with him. I drove 125 miles in his GTI6 yesterday and it was nice having more torque below 4000rpm than a 1.1 Fiesta.

[saveloy 8]

Kris, I'm under attack in 'that' thread of mine. Someone thinks I'm a homophobe. And prejudiced. He has yet to mention sexism, racism, or 16 valvism, but the week is young. Any chance of reinforcements?

[KRISKARRERA 2 1 Cars]

Found this on google: http://www.stuttgartperformanceengineering...ASHPROBLEM.html

Same problem but I need the layman's version.

[jackherer 543]

Found this on google: http://www.stuttgartperformanceengineering...ASHPROBLEM.html

Same problem but I need the layman's version.

 

In l;aymans terms that says:

 

1. Check that your battery light on the dash works

 

2. If it works (comes on with the ignition and goes out when engine starts) there is probably a fault internally to the alternator.

 

3. If the battery light doesn't work check the bulb in the dash

 

4. If the bulb is OK check the small wire on the alternator is connected, not corroded and not broken.

 

5. If the bulb and wire are OK there is probably a fault internally to the alternator.

[KRISKARRERA 2 1 Cars]

Hehe thanks man. See why can't they say it like that on there instead of giving a bloody 24hr lecture!