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dirk1978

Lupo GTI Battery Flat

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Hi all,

The battery on the GTI went flat when the wife did a night shift at the hospital the other day so I had to go and jump start it. It had been sat for a week or so though before that.

After driving for half an hour I left the car for a day and it was flat again. 

The battery is about 3 or 4 years old but it wasn't a top brand. Something from Halfords I think.

What's the order of elimination on these problems? Get a clamp multimeter first to check the power drain, then if excessive it's pulling fuses until it goes down?

Or is it worth just ordering a new battery to see if it fixes it? I'm sure it can't be the alternator because once jump started it was fine while driving.

Cheers.

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Stick your battery on and see what happens.

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Put the battery on slow charge over night, dont use the alternator to charge a flat battery it will stress the alternator. Once it is fully charged then see what it does. or swap a known good battery on as Rich said.

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The most common cause is the central locking. The CCU (convenience unit) thinks a door has just been opened or unlocked and puts everything into standby- often caused by dodgy door switch contacts. Pull the radio and interior light fuses... then watch. :)

 

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On 3/30/2020 at 1:49 PM, mk2 said:

The most common cause is the central locking. The CCU (convenience unit) thinks a door has just been opened or unlocked and puts everything into standby- often caused by dodgy door switch contacts. Pull the radio and interior light fuses... then watch. :)

 

Sorry what do you mean? Pull the radio and interior light fuses before the battery is recharged, or after? And watch what? The current draw? What would pulling those fuses do?

Cheers

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Keep pulling fuses till you can see the battery usage stops... I'd bung a current meter on the + terminal then watch the consumption. Also, deactivate the bonnet sensor while testing. Lock the car then take a reading. Unlock, pull a fuse, lock, measure again. Etc etc...

Edited by mk2

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Thanks (everyone)

I've got a charger turning up today so will let it charge and see what happens. It does sit for days on end and then only get driven a short distance so possibly never gets charged back up.

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Every time you crank an engine to start it (just about every car on the planet), you should run the engine for at least 15 mins to replenish the huge amount of charge you just sucked out of it. That's why cars with start-stop tech have much bigger batteries and alternators, designed to handle the frequent starting cycles.

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So I bought a battery charger, charged the battery full, drove around for a bit and it's been fine.

The wife drove it to work this morning and it cut out in the middle of the road. I went out with jump leads, jumped it, it went a bit further and stopped again.

When it cuts out, the dashboard goes mental with ticking, beeping, airbag and ABS lights first.

It's the alternator isn't it? Hard job on these? It's got aircon.

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It is the alternator.

If you're lucky it's a voltage regular and it shouldn't be much hassle to change.

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You should get a red alternator light (battery symbol) if it's not charging. Especially if you start it with the brakes and headlights on, interior fan on max, and rear screen demistor on. Should glow brightly, indicating a fault. Should also light up just after turning on ignition before starting showing you that the lamp isn't broken.

On many vdub alternators, you can replace the regulator and brush assembly unit for a few pounds (two screws and a nut). Means you don't even need to take it out of the car or mess with the belt...

Edited by mk2

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Oops, I ordered a replacement alternator before reading these. Still waiting for it to arrive. 

The old one was maybe making a bit of a ticking sound anyway. I wondered what it was for a while but it seemed to not be happening after it broke so I assumed it had broken mechanically rather than electrically.

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Yeah, could just be a broken brush that's finally given up.

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I changed the alternator last night. Way easier than I expected. Only needed to raise the car off the ground to get the undertray off because I dropped a spanner in there.

I thought it was going to be a real pain because of the AC but I managed to get it off and out via the top only taking the air duct off. Had to slacken engine mount bolts a bit to allow alternator bottom bolt out.

The old one was a Bosch and after consultation with a mate who's a tech for schaeffler, I got a Lucas reman replacement for £100 + £40 rebate on return.

I charged the battery last night so will check how it goes today with an essential trip to the shop. The only way to check if the alternator is actually charging is with a multimeter isn't it? Clamp around the positive cable? Same to look for drain?

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9 minutes ago, dirk1978 said:

The only way to check if the alternator is actually charging is with a multimeter isn't it? 

Pretty much. You'll be able to tell with a quick check, if it's at 13-14v then it's charging. 

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