# What does part no. 0310 025 015 do?



## JAAYDE (Aug 15, 2006)

After checking the condition on my plugs, i started to put the car back together and the Part number stated in the title (small capacitor 4.7uF and 110v) came off in my hands.. It normally screws in below coilpack 4 on the rocker cover under a bracket.

What does it do? Its also joined to the coilpack loom, can i just solder on a new one or do i need a new loom ?

Ps i can't post any pics as i'm on my phone..


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## John-H (Jul 13, 2005)

I'm inpressed you managed to type in this post if you're on the phone. You must be good at multi-storey tasking :wink: .

I don't see why you would not be able to solder it back on providing it was not broken - but I can't remember seeing it on mine. It sounds like a supressor. I can't find it on the online ETKA - could it have been fitted by someone with an interference problem?


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## JAAYDE (Aug 15, 2006)

If feels like a life time making a post though..;-)

Well it has managed to brake off so it cant be resoldered (just typical)
The car seems to work ok but i don't want it to break down..
I'm also hoping the dealer or VAG will be able to supply me just the capacitor..

Do you recon it will cause running problems disconnected?


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## JAAYDE (Aug 15, 2006)

I managed to salvage the part yesterday evening, by using my demel and cutting into it get more wire exposed so i could solder a new one back on..

Finish result below, but not yet installed to see if it will work.. :? (would help also if i knew what it did :? )










http://i106.photobucket.com/albums/m269 ... G_0612.jpg
http://s106.photobucket.com/albums/m269 ... G_0613.jpg
Below is where it sits in the engine bay..
http://i106.photobucket.com/albums/m269 ... ngine2.jpg


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## John-H (Jul 13, 2005)

Good repair job! I can't remember seeing it on mine. It does sound like a supressor or decoupling capacitor of some sort.


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## jamestown478 (Aug 21, 2010)

I recently broke off the same piece. What type of radio interference does this prevent? would it actually be noticeable it I don't replace it?


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## John-H (Jul 13, 2005)

Might only be noticable in weak signal areas or on AM


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## imranbashir_uk (Mar 25, 2011)

Why don't you email Beru, and see if they can send you a sample?

Contact details here...

http://www.beru.com/english/service/kontakt.php


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## nordic (Apr 26, 2010)

You could, indeed, replace it with a bipolar capacitor of the same rating.
I think it plays significant role in spark quality and timing. 
In theory, without this capacitor, spark appears on falling edge of ECU signal to coil. With capacitor, it appears on raising edge and also stops DC flow through coil winding. ECU expects the spark to happen on raising edge for proper timing.

Kind regards


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## imranbashir_uk (Mar 25, 2011)

It's not as straight forwards as just getting a capacitor of the same rating.

You don't know what electrolyte is used in this capacitor, that will effect its characteristics.

If you buy the capacitor from somewhere like Maplin, it will have a commercial temperature grade (0 - +70C) or at best industrial (-40 - +85C). What you need is an automotive grade.

As I suggested earlier, speak to Beru first see if they can help.


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## jamestown478 (Aug 21, 2010)

what does this part have to do with timing? from what I found from googling it on the internet it has to do with the car radio and nothing to do with spark or ignition?


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## nordic (Apr 26, 2010)

imranbashir_uk said:


> It's not as straight forwards as just getting a capacitor of the same rating.
> 
> You don't know what electrolyte is used in this capacitor, that will effect its characteristics.
> 
> ...


Automotive grade would be ideal, I agree, if such exists, but I haven't seen them easily available. Great if BERU helps, but BERU doesn't make capacitors themselves.

On the other hand, as alternative, it is a foil capacitor wrapped in piece of plastic. Temperature range is there to specify it's expected life within that range and not the range where it won't work. Higher/lower temps will simply degrade life expectancy. After 10 years of heat and cold, original capacitor is most likely dead anyway with massive internal resistance and needs replacing. This capacitor (they are also called ignition condensers) is there to ground ECU pulse after coil. If is it not there, or degraded, pulse finds an alternative way to leak severly degrading pulse strength and time.

Sample circuit..









Radio is sensitive to static, spark produces a lot of static. Here is why coils/ignition lead ends are wrapped into metal shields.


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## John-H (Jul 13, 2005)

I think there's some confusion here. There's only one capacitor (as I remember) but four coil packs. If the capacitor was used as the old "points" spark suppression when cars had points and one ignition coil - where the capacitor helped prevent points erosion and formed a resonant L/C circuit with the primary side of the coil, then there would need to be four such capacitors to go across the "switch(es)" - what used to be points but is now a transistor (4 off - one for each coil) in the coil pack drive circuit. Such capacitors are always best placed in close proximity to the "switch" to avoid the stray inductance down long wires still causing voltage spikes across the switch or transistor.

So anyway, given one capacitor, not having traced it I can't be sure but I'd think it more likely that it was on the +12V side of the loom that feeds all four coil packs on a common single wire. The stray inductance I mentioned will tend to allow this common wire to spike up and down causing EMC radiation i.e. radio interference. The purpose of the capacitor in this scenario is to stabilise this voltage by providing a reservoir to high frequency current demands and prevent these high frequency currents returning back into the main wiring loom and getting to the audio equipment or re-radiating to the outside world. The high frequency currents are kept in a tighter loop - the smaller to loop the smaller the effective antenna area.

I'm not sure what type it is - possibly paper like the old points "condensers" or maybe a plastic film type. Most would work to some extent but the best type for EMC would be a ceramic multiple plate low inductance type but this may not be necessary. Looking at the size of it I'd suspect it was a paper of plastic film type. It's not a polarised electrolytic as that would have the severest lifetime issues. It will be a dry non polarised film cap with no electrolyte, preferably with plate construction rather than spirally wound.


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