Fuse haemorrhage with interesting side effects

[VAG-Slag]

I was driving home on some back roads at about midnight last night at what only can be described as a fair pace when my lights turned off, the car started beeping and the battery light came on!

Lights weren't working at all and I had to turn on my hazards just to see... Weirdly enough my lights came back on 30 seconds later or so but full beam didn't work. The battery light was still on and the car felt under powered so I cruised the last few miles home thinking the alternator could be duff.

I've just had a look and the first thing I looked at was the fuses on top of the battery and found one of them like this:


The worrying thing about it is the fuse hasn't even blown, it's still passing current... And as you can see there was quite a bit of heat generated:


So firstly, what is this fuse for? . . And secondly, has anyone seen this before. Any idea WTF happened!?

 

[<tuffty/>]

Ahhhh ye olde fan fuse issue...

Fans and aircon won't be working then...

<tuffty/>

 

[<tuffty/>]

Should validate this a little... dissimilar metal + corrosion over time causing a bad connection and higher current draw as a result = melting fuse

Worse case is it catches fire... this has actually happened..

Common problem on VAGs with this fuse arrangement

<tuffty/>

 

[VAG-Slag]

Should validate this a little... dissimilar metal + corrosion over time causing a bad connection and higher current draw as a result = melting fuse

Worse case is it catches fire... this has actually happened..

Common problem on VAGs with this fuse arrangement

<tuffty/>

Ok, thanks for that tuffty... Couple of things though, I removed my aircon long ago anyway! Also, why are the high beams not working?

Also, I just fired the old girl up and the alternator doesn't appear to be doing much/anything... A constant 11ish volts (goes down when I put the lights on) across the battery terminals when engine is running. Worth noting that all fuses relating to the the lights are ok

 

[<tuffty/>]

Sounds like the alternator is fubar... dunno on the other stuff... you would have to check the wiring I guess... but if not got much voltage it sounds like the alternator is gone so look at that first then worry about the lights when you know you have juice

<tuffty/>

 

[VAG-Slag]

Sounds like the alternator is fubar... dunno on the other stuff... you would have to check the wiring I guess... but if not got much voltage it sounds like the alternator is gone so look at that first then worry about the lights when you know you have juice

<tuffty/>

yea, the engine's coming out in a couple of weeks anyway so I'll just do the alternator then... Would the main beams need a good 12 or 14 volts to work at all? At the moment i'm only getting 10v when dip beams are on, perhaps that could explain it...

 

[<tuffty/>]

Yeah, 10v is not really gonna cut it dude

<tuffty/>

 

[newbster]

nasty

the other bolt on fuse connections don't look so happy

I think the one on the furthest left is the starter motor, next one acros is the alternator

the alt one look like the crimped terminal is failing, all green and cruddy

I would check if you have continuity down that leg, if not that would explain the low volts

I would also unbolt and clean up all the bolted connections


does your battery say BMW on it? there's yer problem, we know the germans don't play well with others, or themselves

 

[<tuffty/>]

...does your battery say BMW on it? there's yer problem, we know the germans don't play well with others, or themselves

I expect the indicators won't work if thats the case either

<tuffty/>

 

[VAG-Slag]

Yeaaaaah, I'll ad an alternator to the list then... I swear, not matter how much I buy this list just keeps getting bigger! lol

 

[newbster]

alt may be ok, that second power cable in from the left looks a bit iffy, i'd check that first
/m

 

[Prawn]

Those fuses were dodgy when I sold it to Pierre 3 years ago, you've had a good innings I'd say

 

[VAG-Slag]

alt may be ok, that second power cable in from the left looks a bit iffy, i'd check that first
/m

Yea, I might have a go at cleaning that up tonight... You'd expect a bit of voltage from the alternator to pass through that though, surely!?

Those fuses were dodgy when I sold it to Pierre 3 years ago, you've had a good innings I'd say

Yea, thanks for letting me know, "buddy"!

 

[westcoast a3]

Bit late but

 

[newbster]

that's funny right there ............I like

 

[VAG-Slag]

Ha ha! . .

All jokes aside... I just cut that dodgy lookin wire back to some clean wire and reattached and still the same.

Also I noticed then when the engine stops there's a horrid grinding/wiring noise from the alternator as it winds down, so I'd most deff say a rather knackered alternator!

 

[newbster]

bummer

if its a bosch, you can fit one from a3/golf upto about 2010 model, I did a thread on it a while ago

 

[newbster]

this one
http://www.audi-sport.net/xf/threads/cheap-alternator-replacement.237573/

 

[VAG-Slag]

this one
http://www.audi-sport.net/xf/threads/cheap-alternator-replacement.237573/

That's good information... I didn't fancy sticking another 10/15 year old unit on for fer it's probably be on it's last legs anyway, will deff have a look into this though. Thanks!

 

[newbster]

the bosch and valeo are a direct swap, I prefer bosch
I used ECP to get the dimensions and plug connector of my old alternator, then had a look an ebay to see what was available,
I screwed up slightly and got a 2012 unit, the engine light plug was slightly different and it did not work, but as I said, you can get a new regulator with the older style connector and its works, straight swap.

I recall the 2010 bosch should be a direct swap.


the important bit is the small connector

needs to look like this

the ribs sticking in from the side need to be the same,

there are some on the bay for about 50 quids atm,(2010 golf) but you can't see the connector, maybe ask seller for a better picture of the connector?

the new one was about 10mm longer on the back, not a problem on tdi, not sure on the S3

 

[VAG-Slag]

What do people think the highest ampage alternator I should be looking at is? . . I saw a 180 amp one ebay the other day, thought that might be a tad over kill though! lol

 

[Samuealle]

I might have an S3 one knocking about. If I do. Meet me at the services where the m4 meets the a34 at Chieveley and grab it. Wont cost you a penny buddy.

 

[VAG-Slag]

Yeah, 10v is not really gonna cut it dude

<tuffty/>

Riddle me this... So I now have a fully operational alternator, getting a good 14v across the battery terminals. However still no full beam :-/

All fuses good, bulbs haven't blown.... What now!? lol

 

[newbster]

oopsies

when you say high beam don't work, is that not even when pulling stalk back for "get out of my way" mode

which fuses did you check - numbers

looking at the wiring diag, the lighting stalk looks a favorite, but Haynes manual is not too good on wiring diags, anyone got a decent one?

oddly enough, low volts from the alternator can actually cause more current to flow, opposite of what you would think,, the low volts allows the bulbs to go dim, and cool off a bit, the resistance then goes down which allows more current, so may have burnt out the contacts in the stalk.

 

[VAG-Slag]

oopsies

when you say high beam don't work, is that not even when pulling stalk back for "get out of my way" mode

which fuses did you check - numbers

looking at the wiring diag, the lighting stalk looks a favorite, but Haynes manual is not too good on wiring diags, anyone got a decent one?

oddly enough, low volts from the alternator can actually cause more current to flow, opposite of what you would think,, the low volts allows the bulbs to go dim, and cool off a bit, the resistance then goes down which allows more current, so may have burnt out the contacts in the stalk.

Pull back "YOU ****!" mode doesn't work as well as normal flip forward... The blue light on the dash does come on though which suggests the stalk is working fine.

I checked all the obvious fuses and even some that might be distantly related to lights in any way, couldn't give you numbers at the moment, but I checked loads!

 

[newbster]

yea, I meant to add that if the blue light on the dash comes on then there is some functionality in the stalk

so, how did you determine the bulbs are ok? are you really really sure??
/m

 

[VAG-Slag]

yea, I meant to add that if the blue light on the dash comes on then there is some functionality in the stalk

so, how did you determine the bulbs are ok? are you really really sure??
/m

Just a visual check on the bulbs... Filaments looked absolutely fine, I'll check if there's any voltage getting to the connectors tonight though.

If not I'm wondering if some wiring has melted somewhere and whether this is related to my reoccurring 17748 fault. . . .

 

[newbster]

if you have access to a DVM then i'd check the bulbs with that, I've had bulbs that looked ok but were actually dead
/m