Electrics: - Help me diagnose headlight fault please

Dory2 · Aug 6th, 2015, 16:16

O/S headlight doesn't work. The bulb is fine but there is 0 volts on the connector. Fuse is fine. What should I check next? Thanks for your help.

Alex121 · Aug 6th, 2015, 16:30

Hi,

Take out your CEM and replace the relay. That would be the next step.

http://www.volvoforums.org.uk/showthread.php?t=67584

Dory2 · Aug 10th, 2015, 17:34

What a clear and well-written guide to the CEM. Three cheers for Russel S!

I replaced the RH dipped beam relay but the headlight still doesn't work. I've got 12 volts at the fuse but 0 volts at the bulb. I guess I should have checked that BEFORE breaking out the soldering iron. Am I right to assume that there's a break in the loom somewhere? I can't think why that would happen; I've not had an accident and the loom is securely anchored. Is there anything else I can check? Or is it time to simply run a new wire from the fuse to the bulb?

druid · Aug 10th, 2015, 17:42

Loom of death? under the rad'. Common enough as these cars age.

gatos · Aug 10th, 2015, 19:00

I missed the original post. The relay is at fault, only when you are getting 0V when the bulb is plugged in and 12V with the bulb unplugged.

In your case, it seems that it is a wiring problem and most probably it is in the main loom under the radiator. If not, the second weak spot of the loom is behind the driver's wing

See the guide here of how to access the wiring loom under the radiator: http://www.volvoforums.org.uk/showthread.php?t=144411

druid · Aug 10th, 2015, 20:35

Before you panic to much, how good are you at soldering, have you cocked it up? Not dising you but how likely is it?
Good luck!

Dory2 · Aug 10th, 2015, 20:41

Well, it turned out to be nothing more than a blown bulb. Here's a top technical tip: there are four headlights: two full beam and two dipped. It turns out that you cannot check if a dipped beam bulb is ok by looking at the full beam bulb next to it. Who knew?

DOH!

druid · Aug 10th, 2015, 20:57

Quote:

Originally Posted by Dory2

Well, it turned out to be nothing more than a blown bulb. Here's a top technical tip: there are four headlights: two full beam and two dipped. It turns out that you cannot check if a dipped beam bulb is ok by looking at the full beam bulb next to it. Who knew?

DOH!

Congratulations

How are you now?, was it a senior moment?
Love it when people have the nads to fes up!

neanderthal · Aug 10th, 2015, 21:02

now? lol

druid · Aug 10th, 2015, 21:30

Quote:

Originally Posted by neanderthal

now? lol

Ok Ok ,fair.
FIXED lol

Aug 6th, 2015, 16:16	#1
Dory2 New Member Last Online: Jul 15th, 2018 17:10 Join Date: Sep 2014 Location: Northampton	Help me diagnose headlight fault please O/S headlight doesn't work. The bulb is fine but there is 0 volts on the connector. Fuse is fine. What should I check next? Thanks for your help.

Aug 10th, 2015, 17:34	#3
Dory2 New Member Last Online: Jul 15th, 2018 17:10 Join Date: Sep 2014 Location: Northampton	Changed the relay, still no light. What a clear and well-written guide to the CEM. Three cheers for Russel S! I replaced the RH dipped beam relay but the headlight still doesn't work. I've got 12 volts at the fuse but 0 volts at the bulb. I guess I should have checked that BEFORE breaking out the soldering iron. Am I right to assume that there's a break in the loom somewhere? I can't think why that would happen; I've not had an accident and the loom is securely anchored. Is there anything else I can check? Or is it time to simply run a new wire from the fuse to the bulb?

Aug 10th, 2015, 17:42	#4
druid V40 Owner Last Online: Dec 13th, 2020 01:28 Join Date: Aug 2006 Location: Tonyrefail, Souh Wales. View Photos By: druid	Loom of death? under the rad'. Common enough as these cars age. __________________ *An MS Warior living one day at a time* "Neville" 207,000 so far. Water use 0 - oil negligible....

Aug 10th, 2015, 19:00	#5
gatos Premier Member Last Online: Nov 15th, 2022 21:34 Join Date: Apr 2010 Location: London / Essex	I missed the original post. The relay is at fault, only when you are getting 0V when the bulb is plugged in and 12V with the bulb unplugged. In your case, it seems that it is a wiring problem and most probably it is in the main loom under the radiator. If not, the second weak spot of the loom is behind the driver's wing See the guide here of how to access the wiring loom under the radiator: http://www.volvoforums.org.uk/showthread.php?t=144411 __________________ Current car: 2002 S40 1.9D, 1992 240SE Nullius in Verba

Aug 10th, 2015, 20:35	#6
druid V40 Owner Last Online: Dec 13th, 2020 01:28 Join Date: Aug 2006 Location: Tonyrefail, Souh Wales. View Photos By: druid	Before you panic to much, how good are you at soldering, have you cocked it up? Not dising you but how likely is it? Good luck! __________________ *An MS Warior living one day at a time* "Neville" 207,000 so far. Water use 0 - oil negligible....

Aug 6th, 2015, 16:30	#2
Alex121 Premier Member Last Online: Oct 27th, 2020 10:45 Join Date: Nov 2011 Location: -	Hi, Take out your CEM and replace the relay. That would be the next step. http://www.volvoforums.org.uk/showthread.php?t=67584

Aug 10th, 2015, 20:41	#7
Dory2 New Member Last Online: Jul 15th, 2018 17:10 Join Date: Sep 2014 Location: Northampton	Final diagnosis: I'm an idiot! Well, it turned out to be nothing more than a blown bulb. Here's a top technical tip: there are four headlights: two full beam and two dipped. It turns out that you cannot check if a dipped beam bulb is ok by looking at the full beam bulb next to it. Who knew? DOH!

Aug 10th, 2015, 21:02	#9
neanderthal Master Member Last Online: Feb 10th, 2022 10:02 Join Date: Jun 2011 Location: THE MINSTER MAN View Photos By: neanderthal	now? lol __________________ volvo v50 2.0 se lux D estate 2007 s/h volvo v40d estate 2003

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