Author Topic: GTi 1.8T, strange rythmic noise, revs pulsing lightly, lights dimming.  (Read 3009 times)

Offline jlbrown3

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I started my car last night and noticed an unusual noise at regular intervals (3 seconds or so), the noise is accompanied by a slight drop in revs and also dimming of lights.  The noise "sounds" like a pump?  I've had a long running problem with this car:

http://www.golfgtiforum.co.uk/index.php?topic=52613.0

I wonder whether this the problematic component finally giving up the ghost after 2 years, umpteen times on the computer and new MAF and temp sensors.

Has anyone experienced similar problem or have any ideas?  I'm wondering whether to risk the 25 mile journey to my regular mechanic or just take the £££ hit at the dealership on my doorstep.

John

Offline ben1.8T

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Could this be the secondary air pump?
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Offline Rhyso

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if your lights are dimming i'd suggest that your alternator may be on its way out

do the lights dip if you use any other electrics? i.e windows etc?

Offline Sean_GT

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mine does that, the revs drop now n then when i pull up at lights and stuff with clutch in, sometimes, the revs take time 2 drop, and then they drop below 800 and flicks up n down, lights did dim now n then when putting windows up and down but i thought nothing of it, i was putting it off hoping it wud stop but maybe there is a fault
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Offline theshrew

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If your lights are dimming and its making a noise i will bet that will be your alternator mate.

Take it anywhere they will prob test it for free for you as it only takes 2 min to check or check yourself with a multi meter if you have one or can borrow one.

Attach it to the battery see what it reads on tickover shud be about 11 - 12v rev up you shud see the volts go up to about 14V or somthing along those lines if its working correctly.

Offline barry-gti

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mines done it a couple of times an revs were dropping to about 600-800 revs, first time was after a 60 mile motorway drive

Offline jlbrown3

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The alternator sounds very plausable, I wonder if my on-going intermittent problems since Jan 07 (linked in my original post) have been this or something else electrical.  If only it could be that simple!  Will get checked and report back.

Offline topher

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turn your aircon completely off and go for a test run to see if it still happens

Offline jlbrown3

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turn your aircon completely off and go for a test run to see if it still happens

Frustratingly as usual I can't replicate the exact problem; revs jump a couple of hundred when I turn on the aircon or turn the steering wheel if that means anything?

Offline topher

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I'd say it's a combination of your aircon compressor or rad fans kicking in, and a slightly dodgy battery or alternator making you more aware of it as it draws the power away making your revs drop/lights dim for a moment or two. Most garages will be able to put a tester across your alternator to show if its that or your battery that needs replacing.