Headlights and dashlights flickering

[Jim Bowen 1]

May be unrelated to the new battery I fittef the other day.

 

Have noticed when sat idling with headlights on. I get a slight flickering of the headlights and the mfa display.

 

Its sort of pulses with the engine. I seem to of noticed a slight lumpiness at lower revs when driving. That could unrelated. Maybe coilpack or leads.

[vw rule 19]

Hello there,

 

could be a bad earth or a slight fault with the alternator,

if you have a slight misfire it normally won't affect the charging system.

 

Check tension of alternator belt.

Check charging rate from alternator at idle with all electrics off,

should be around 13.5 volts to 14 volts.

 

Then check with most electrics on again at idle, should see around 12.8 volts to 13 volts,

if you rev the engine to 2000 RPM and hold there, you should see around 13.5 volts.

 

With a full electrical load on i.e lights, heater blower, rear demister screen,

at idle you normally see 13 volts and if you rev the engine as above you should get a reading of 13.5

Any lower then 13 volts at fast idle and your alternator may need to be repaired / replaced.

 

Corrado 1.8 & 2.0 16v have V= belts (both alternator & power steering belt)

(V=belts you adjust manually, should be able to twist the belt by 45 to 90 degree,

or 5mm to 7mm movement if checking tension.

 

Corrado 8V, G60 & VR6 have Ribbed alternator belt

(Normally have auto tensioner so high tension is on these ribbed belts)

(if manual tensioner then should have around 2mm to 3mm movement anymore and the belt will be loose and will slip)

 

 

Hope this helps.

 

Si

[Jim Bowen 1]

Thanks for this. Going to try and investigate this weekend. Hoping its just an earth as alternator was meant to be quite new or reconned unit.

[fonzooorooo 10]

I've just sorted this exact issue on our mk2...

 

I've cleaned up and re-seated the big earth cable onto the engine and chassis and changed the voltage regulator on the alternator. (£10 off ebay!) ... The voltages measured OK before, but the brushes (part of the regulator) were well worn (down to about 1/2 the length of the ones on the new regulator). All appears well after that!

[Jim Bowen 1]

I've not done anything with it yet, but had read other peoples thread and they mentioned the voltage regulator. Is it easy to change? I have 3 alternators at the moment :lol:

[fonzooorooo 10]

They just screw onto the end of the alternator (2x M4 machine screws - X head on Bosch, - on Valeo - dead easy! Life's easier with the alternator removed for the sake of 2 bolts!

[Kevin Bacon 5]

VR6 alternator isn't quite as easy, but yes, that is what the issue is.

 

If you put a voltmeter across the battery with the engine running, you'll see the voltage pulse up and down slightly at the same rhythm as the light flickering. The regulator is dying and allowing AC voltage through, which DC electronics aren't especially fond of.

[Jim Bowen 1]

Did the meter on battery and was going from 14.28 to 14.32 with engine running etc, Wasn't much in it, tried to sort out the earths but made no difference.

 

Not sure what else to check, i ran a new earth lead from the battery to the chassis.

[Jim Bowen 1]

Fitted new alternator yesterday and solved the issue. The other alternator sounded/felt a bit grindy when i spun it by hand.

 

Didn't need to remove the front end or jack the engine up. Like Kev says it came out though the gap left by removing headlight/grill. Removed a 120a which must be larger as it was extremely tight getting it out and the 90a went in with ease. Removed air box and belt tensioner.