2010 C5 x7 2.0 HDI Tourer Dip beams sudden failure

[electronmirror]

As per the title, both dip beams failed simultaneously.

I've checked the fuses under the bonnet (F17 and F18 15amp according to the vehicle handbook). Both good and no corrosion evident.

Both dip bulbs checked off the car, both light up. Quick check with DMM shows lack of power to the dip bulb connectors on both sides.

Main beam and ALL other lights working normally.

Are the lights fed by relays, if so where are they?

Any other 'usual suspects' as far as this failure is concerned?

[bigblackfalco]

Cue a BSI reset!

[Paul-R]

The fact you were able to use a meter implies that your car has halogen bulbs. Can you confirm?

[electronmirror]

Yes, the car has conventional halogen bulbs.

The BSI reset (done twice) did not resolve the problem.

[RichardW]

I think they have separate fuses and relays in the fuse box. So if they've both gone down that would suggest loss of signal, you need to get it on a diag machine to see if the stalk unit is sending the signal.

[bigblackfalco]

Is this both on Auto lights and standard ON?

[electronmirror]

Yes, it’s the same whether on Auto or the normal ON position.

The Lexia laptop is now on charge ready for tomorrow morning’s diagnostic session but the forecast for Sat morning says 2*C

[wheeler]

Is there power at both the fuses when lights are switched on? I would probably give the fuses a 12v feed to see if the lights illuminate confirming the wiring is ok.
Failing that if diagbox can 'see' the signal for the dipped beam operating then it has to be a faulty BSM (PSF1), the relays are an internal part of the BSM.

[electronmirror]

So we have power on both fuses (F17 and F18) when the stalk is switched on for headlight dip beam.

From the diagnostic session: 'dipped beam illumination request' toggles between 'yes' and 'no' when the stalk switch is selecting between headlight dip and off.

and : 'dipped beam illumination control' toggles between 'active' and 'inactive'.


So if the BSM (PSF1) is faulty any thoughts on the likely failure mode and is it repairable by dismantling and then component replacement/soldering etc. ?

[wheeler]

I would say if the fuses go live when the lamps are switched on then the BSM is working ok? The fault must be after the fuse box.

[xantia_v6]

Does the voltage get as far as oins 25 and 26 on the 28 way brown connector on the BSM?

[wheeler]

I’d be looking at disconnecting the fuse box connector & sending 12v down the wires to see if the lamps illuminate

[electronmirror]

The OP is a PLONKER !!

You know how it is when you think you know something, then you convince yourself that you know something and........

Having spent an hour or two removing the fuse box and then separated the two halves for a good look to see if there any obvious problems , none found. I then reassembled it and reconnected all the wiring.

The bulbs that I removed and bench tested were..........THE MAIN BEAM ones NOT the DIP BEAM ones

So the problem all along was two blown dip beam bulbs....I thought I knew the difference between main and dip headlamp locations....

Many thanks to all those who offered suggestions to this plonker who ought to have known better.

Ted

[bigblackfalco]

The OP is a PLONKER !!

You know how it is when you think you know something, then you convince yourself that you know something and........

Having spent an hour or two removing the fuse box and then separated the two halves for a good look to see if there any obvious problems , none found. I then reassembled it and reconnected all the wiring.

The bulbs that I removed and bench tested were..........THE MAIN BEAM ones NOT the DIP BEAM ones

So the problem all along was two blown dip beam bulbs....I thought I knew the difference between main and dip headlamp locations....

Many thanks to all those who offered suggestions to this plonker who ought to have known better.

Ted

I love stuff like this! Obviously this kind of thing has never happened to me.
Surprising that both bulbs had blown.
An easy fix!

[RichardW]

Well done on admitting it! What often happens is that one is out and you don't notice, then the other goes and you think both have gone at the same time, cue looking for some upstream fault!