What is causing headlamp bulbs to blow out?

ProudDUB

My headlamp (drivers side) has blown a bulb for the third time in as many months. Any idea what could be causing this? The car is a 2007 Ford Focus.

I had the entire fixture replaced back in October, as the glass in the headlamp was cracked. (I would have failed my NCT if I went in with it cracked.) Last month, the light stopped working again. Replacing the bulb fixed the issue, but now it's gone again.

I'm taking it in tomorrow to have it looked at, but I'd rather be armed with some knowledge of what could be going on. I don't want them to put in another new bulb & send me on my way, only to have it go again in another couple of weeks, when I am on some dark country road.

Could some damp have gotten into the cars electrics when the light casing was cracked and messed with the electrics? What kind of standard diagnostics will they do to get to the root cause of the issue, and how much could I expect to pay for it?

Cheers.

Atlantic Dawn

Are you wearing gloves when changing the bulbs? If your not that could be causing them to blow early if the glass is making contact with your hands, bulbs will be black in appearance.

ProudDUB

I'm not the one changing the bulbs. The garage has changed them. I don't know if they put a new bulb in, when they replaced the whole light fiting back in October. When the light stopped working a few weeks ago, I took it back to them and they just replaced a bulb. It was fine for a few weeks, but now its gone again.

Hal1

If it was handled correctly the other thing to check would be moisture inside the headlight or corrosion on the bulb holder contact would cause it to blow in a short time. The other thing that would cause this would be a weak alternator. A garage can do a test on it under load to see if the voltage is right.

slimjimmc

Cheap low quality bulbs?

dollybird2

I know a few focus owners with the same issue. Bulb blows once car goes over a bump or into a pothole - any jolt. Is there condensation inside the unit? Could the fitting be loose? Possibly a focus snag also...

Dark sun

Seen this happen on an older focus, where a headlight bulb would blow after a week or two, was back a fort to garage 3 times getting them replaced, what I done was changed both headlights at same time, sorted the problem, strange but did the trick.

Cheap bulbs or excessive voltage to them, there the first two things I would check.

braddun

https://uk.answers.yahoo.com/question/index?qid=20121202045105AAKIXMb

visual

Connections to bulbs is most likely the problem
The should be tight fitting and have no corrosion or look like they have over heated at anytime. If they show any of those symptoms change the bulb socket

dr.fuzzenstein

Dark sun wrote: »

Seen this happen on an older focus, where a headlight bulb would blow after a week or two, was back a fort to garage 3 times getting them replaced, what I done was changed both headlights at same time, sorted the problem, strange but did the trick.

+1, exactly that.
On my Focus, if one bulb blows, they both have to be changed at the same time. After that it doesn't matter if they're cheap and potholes won't matter.
Once I replace both bulbs at the same time, they will last about 2 years.
I have used Halford's bulbs for the last few years and they are fine.
I'm currently using the Halford Heavy Duty bulbs and they have lasted for a few months already.

Harcrid

May also be a frayed wire somewhere. I had this on a previous car when it would blow bulb the odd time I hit a bump. Airbox had frayed a wire through friction when moving around and shorted it causing bulb to blow.

ProudDUB

Thanks for the replies folks.

Ok, so things to ask at the garage tomorrow:

1. Are you using cheap bulbs?
2. What about putting replacement bulbs in both lights, even though only one of them is gone?
3. Frayed wire?
4. Is there moisture inside the casing?

The thing is, I don't think that the light bulb fitting itself is the problem. When I had the whole fixture replaced 2 months ago, the light was still working, even though the glass in the headlamp fixture was cracked & had been for some time.

dr.fuzzenstein

Well, from my own experience I can only say that every single time I replaced one bulb on it's own, it would blow within days of me doing this. I once replaced the left headlight bulb 3-4 times in a row. Guy at the motorfactors then advised me to always replace in pairs. I thought this could also be related to the spare bulb being a different type.
So fast forward a few years later and I put in a pair of cheap GE bulbs from Halfords and one blew a few months later. Fine, thought I, I know the exact type of bulb, they're relatively new, let's replace only one.
2 days later blown bulb.
So got a pair of heavy duty Halford's bulbs and all is well so far.
It may be worth noting that it is always the driver's side bulb that blows in my case.
Wiring, headlight unit and connector is fine.
So far I can 100% back up that a single bulb replaced on it's own will ALWAYS blow within a few days and bulbs replaced as a pair will always be fine. I drive a 2006 CMax, but electric system should be the same.

pablo128

ProudDUB wrote: »

Thanks for the replies folks.

Ok, so things to ask at the garage tomorrow:

1. Are you using cheap bulbs?

Do you expect them to admit they were fitting cheap bulbs?

Why don't you fit a pair of bulbs yourself? It's not rocket science. One screw at the very top of the headlight, and the whole unit slides out towards you giving plenty of room.

Squatman

ProudDUB wrote: »

Thanks for the replies folks.

Ok, so things to ask at the garage tomorrow:

1. Are you using cheap bulbs?
2. What about putting replacement bulbs in both lights, even though only one of them is gone?
3. Frayed wire?
4. Is there moisture inside the casing?

The thing is, I don't think that the light bulb fitting itself is the problem. When I had the whole fixture replaced 2 months ago, the light was still working, even though the glass in the headlamp fixture was cracked & had been for some time.

Nope, you ask the garage, "why is it blowing so many bulbs" and "what have you done to ensure this will last longer than the last bulb"