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Hi all,

I have a '98 MKIV with HID headlamps and every now and then one of them goes out. If I turn the lights off and then back on, it comes back on OK.

I have just changed the bulbs as I thought it was that.....but it's the same.

Any ideas what it might be?

Thanks

Mike

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Hi Mike,

It's not the bulbs so you have either some intermittent wiring problem or a failing ballast unit,I think you need to go in there and give the loom a good shake if nothing shows up maybe swap the ballasts over to see if the fault moves to the other side.

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OK, dumb question.....

What does the ballast pack look like, where is it and how easy is it to swap over?

Ok, 3 dumb questions, but this is my first experience of HID's :)

Thanks

Mike

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Hi mike, the ballast boxes are about the size of a couple of fag packets together, maybe a little bigger. Just trace the wires out the lamps back to them. Mine were aftermarket so I know where they are lol.they can't be far from the lamps

Steve.

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mine did this when I had leaky seals, i've never changed the bulb or the ballast and they've been fine since I dried out the moisture and improved the seal

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This is a generic picture on the link but if you as suggested follow the loom from the bulb you should come across something similar.

http://www.hidkits.co.uk/images/D/ballast_top_500.jpg

I forgot to mention these things use a very high voltage to initially strike the arc in the lamp so be careful,if you want to tap the unit to check for intermittent operation use something insulated or a big stick like Janey uses for non conforming club members :whistling:

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I've replied to you on eBay but so that the info is here for everyone, the ballast unit on the MKIV is on the underside of each headlamp. It's all one piece with the headlight level control, and as a result none of the high voltage wiring is ever exposed outside of the headlamp unit.

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OK, I've got an update and a new question.

Today, I have swapped over the ballast packs and the fault stayed on the driver's side.

All the wiring looks ok with no obvious breaks and wiggling the wires made no difference. Bear in mind that one the light goes off, if I turn the lights off and on again, the light comes on as usual.

My question is, could this be down to the headlamp relay? If so, does anyone know how much a new one would cost?

Thanks

Mike

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Well,

I've had a mad day of it today.

I ordered a new relay from Maurice (thanks mate it turned up today) and fitted it today. The drivers light went out after about 20 minutes, so this evening I......

Bypassed the relay

bypassed the fuse and fuse box

Fed a new earth feed directly to the ballast pack, thus bypassing all the car's - wiring

Fed a new live feed directly to the ballast pack, thus bypassing all the car's + wiring

All this LED me to one conclusion......it MUST be the bulb, even though it's been doing it since I fitted it. So as a last attempt to pinpoint the problem, I swapped the bulbs...now the passenger's headlight goes out after about 20mins, proving it's the bulb.

So what's the chances of driving home one day and your drivers light goes out after 20mins. You buy a new set of bulbs and replace them. 20 mins after switching the lights on, the drivers light goes out, leading me to think it's something else....Just goes to show, just because something is new, it's not a certainty that it's fault free.

I have asked the eBay seller to send me another bulb and when/if he does and I fit it, I will test the lights to prove my theory and confirm to you.

Thanks

Mike

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