Xenon Headlights (2011 Mk4 Mondeo) - both failed at once?

[breamster]

Driving late last night, I put the full beams on for the first time in a while. As I was driving both full beams failed and went back to dipped beam.

I checked the fuse and all OK.Surely both bulbs can't fail simultaneously?

Ordinarily I would just bung in some replacement bulbs and see or check with a multi-meter etc. However with Xenons I am looking at £100 a pair or some such craziness. I do fancy getting something a bit brighter as I will likely be doing a lot of night driving soon but i don't want to spend the cash if there is some other fault.

Is there any way I can test a xenon bulb? Any common faults with these? Is it likely that both failed at once?

Thanks in advance.

[breamster]

The dipped beam did stay on when the full beams failed. Difficult to know without taking the headlamp assembly apart. The main bulb is concealed behind a very domed lens.

I do have the blue light on the dash light up so was hoping that the switch is ok. Perhaps I have a duff relay after all?

For a laugh I called the local ford dealer for a price on replacement bulbs. £162 each!! Yikes.

GreenV8S said:

Does the low beam stay on with the high beam on that car? On my Mondeo it's one or the other.

If the low beams switched back on when the high beams went off that would make me suspect a switch/wiring type of problem. If the low beam stayed on the whole time that's consistent with a bulb or fuse failure. I guess it's possible that one bulb blew and caused a surge that took out the other one - I haven't seen that on a car, but I've seen it with mains voltage bulbs which I guess are broadly similar.

[breamster]

Someone at work has suggested the ballasts may be faulty? Thoughts anyone?

[breamster]

Sorted! Phew. Dodgy fuse after all. I had tested it and it was ok. Replaced fuse anyway and lo and behold there was light!!!!

[breamster]

GreenV8S said:

Cool - good to have a resolution.

Bum. Spoke to soon. Fuse has blown again. Does anyone have any ideas? I'm not actually sure now if I have halogen or xenon? How can I tell?

Thanks.

[breamster]

Righty ho.

I've had a look and I'm pretty sure they are Xenon. They have what look like ballasts in the back of the headlight unit.

Difficult to have a proper look - the joys of leaving for work in the dark and getting home in the dark and no cosy lit garage to work in.

I've changed the fuse again albeit with a different brand of fuse just in case.

The fusebox look spotless as it is under the glove box inside the car. Both headlamps are dry and there is no condensation in either of them.

Lets see if I blow them again over the next few drives.

[breamster]

Ok. It lasted one drive. Any ideas? Everything seems too expensive for trial and error? Reluctant to take it to Ford!

[breamster]

GreenV8S said:

You said it was a failed fuse last time. Has the fuse gone again this time?

Yep.

[breamster]

Penelope Stopit said:

What is the number of the fuse that keeps blowing?
Have you located a wiring diagram and if so can you share it so that I can take a look?

Thanks Fuse is F9 under the glovebox - will do some googling to try and find a circuit diagram - very logical I should have thought of it!

[breamster]

tapkaJohnD said:

repeatedly failed fuse = too much current for the circuit, and the fuse.
Something is drawing too much current.

I don't know enough about the electronics of Xenon bulbs to say about that, but a worn bit of loom and a short to earth is the other explanation.
Try a multimeter across the wires between lamps and fuse, ignition off, jiggling the circuit. Does an earth suddenly appear?

John

I'm not particularly skilled with a multi-meter but I've jiggled as much as I can with no sign of an intermittent earth.

On the occasions I have blown the fuse it is when I've had them on for 20+seconds driving at night. They have not blown when I have used them flash people out of junctions etc. Not sure if that makes any difference.

[breamster]

Fastdruid said:

Have you got the swivelling headlights?

Having replaced a bulb in mine it did concern me that there appeared to be nothing special on the wiring to allow them to swivel. It concerned me that if it was located a bit wrong it would wear out the wiring in not that long.

Thanks. Nope. They don't swivel but they do auto level.

Fuse is only for the full beams, normal headlights still work as intended as does the levelling.

[breamster]

Penelope Stopit said:

I have searched and searched more for a diagram with no joy and without one things get difficult
There is a way that you can prove if it's a LH or RH headlight fault but it will take a bit of work and a diagram will help save much time
Has anyone access to a diagram for this car?

Are you able to get stuck in and do a bit of wiring to help prove what is causing the problem if a wiring diagram doesn't show up?

Thanks for your efforts - I do appreciate it!

I've had a look as well and not found anything. Still looking. I am a bit wary of doing too much wiring - I have experience of burning insulation off of wires with nice puffs of smoke.

Presumably I could try unplugging one headlamp at a time and see if the fuse blows? If I put full beams on for a few minutes (in the drive) it should blow if it is going to. Would that help?

I've only just got home - dark when I leave for work and dark when I get home. I really don't like this time of year. Too late for me to try it tonight plus I am tooo tired. Will try it tomorrow.

Thanks!