Xenon headlight dead, now both dead!

S

stevenoow

Member
Hi all,

I need a bit of a heads up as to what might of happened to my lights.............

I recently had a new control module fitted under warranty at my garage approximately 1 month ago if that as it was corroded and failed, since then the headlights have still been quite wet inside so I ordered 2 new headlight backs, I read on a post on here that to remove moisture from the headlight you can remove the back and drive it with the lifts on and this should clear it which I have done before and worked a treat, so this afternoon I did such that,

Unfortunately it started to rain very lightly, I was aware I would have to drive home without the backs on with light wetness on the road but it's only 8 miles from where I work, within half a mile the light failure sign came up on my dashboard, bugger :cry:, the opposite side in which has just been fixed was out (xenon headlight), i then had to stop 2 miles before I got home to buy a train ticket and when I got back into the car and turn the key to sart the car to my despair the the other side had died as well, I had to drive the rest of the journey with just fogs on

I removed the little back plastic wheel arch light access cover to see if water had got in as the back wasn't on but there was hardly any water anywhere, I saw one or two drops

Can anyone help on this matter, I really can't see how the back not being there could kill both light within 15mins of each other, maybe a fuse perhaps? The car is now booked into the garage that fixed it first time, sorry to go with the story but trying to give as much information as possible

Any ideas/help would be more than appreciated.....
 
The only thing I can add is my drivers light was letting in water/condensation from the lens seal at the top of the front of the light not the back then the bulb went (so I thought) but it was the xenon unit blown as well so the water and blown unit is no coincidence! I've been lucky to get a recon unit from a friend and the leak sealed £55 .
Get your man that's doing yours to check for leaks in the front lens unit as I've now found out it's not just the back of the lights that let in water. Good luck
 
No backs, rain, near simultaneous bulb failure, are all too much for mere coincidence, they are related. I submit the following for consideration. It is all speculation, don't take too seriously, yet may be something to think about.

Xenons, as we all know utilise extremely high voltages to invoke an illuminating electrical discharge. At these voltages, materials that are normally insulators can become conductors, especially in high humidity environments. There does not need to be visible moisture, saturated air is enough to cause the voltage to find alternative paths to ground. Once enough current finds its way to ground through alternate paths, there is no longer enough current to create the plasma path essential to illumination and the bulb fails.

This is not necessarily a permanent failure. If the components can be properly dried out and then protected from further moisture, they could work fine once again. Unfortunately, once something that is sealed to prevent moisture ingress gets wet, it can be very difficult to get it dry again. Moisture resistance works in both directions.
 
If the backs weren't on and it was raining then I would guess that the xenon control modules that are bolted to the underside of the headlight have both failed because of water ingress.

The water gets into the sealed control unit via the wire connector and fills up inside. The water cannot get back out and once the circuit board inside is submerged the unit will fail.

I had my car parked up for 2 days without the back cover on and it was raining. The water got into and killed the control unit. I believe the water running down the bonnet managed to find its way into the back of the headlight as the cover wasn't on.

When I took the control unit out I could shake it and hear the water inside. I replaced it with a 2nd one from ebay.


Cheers
 
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