 You don't need to be an 'investor' to invest in Singletrack: 6 days left: 95% of target - Find out more
2007 Citroen Relay.
Last trip out and a light fault warning lamp comes on. Check the van and front and rear side lights both out. Did a bit of research and found that some vans have a fuse for this circuit mounted in an optional fuse box in the door pillar while others have the circuit controlled by the Canbus system.
Our van doesn't have the fuse box so to start with I changed bulbs. Couldn't see anything wrong with either bulb but fitted new replacements in both. Disconnected the battery for 30 min to reset the canbus and clear the fault. Turned on ignition and warning light had gone. Turned on lights and warning light came back on and still no lights.
It's a bit difficult to diagnose as the canbus cuts power to the circuit so no way for check for a live feed.
Next, I thought I should see if there were any other signs. Put indicators on and they were working but soon started flashing fast like when you have a blown bulb, this hadn't happened before so had a look around the van and noticed all indicators were working but the rear one was very dim. So I thought this could be a fault with the earth to the rear light cluster. Stripped it down, identified the earth pin in the connector and sure enough it was corroded and the reciever in the multiplug had it's contacts splayed wider than the others. Cleaned it all up and tightened the contacts, put it back together and tested. Started with indicators and all working good and bright. Turned on side lights and fault light came back on with no side lights working. Turned on headlamps and fault light went out and side lamps came on. Turned back to side lights and fault light came back and lights went out. Turned back to headlamps but fault light stayed on and still no side lights. Wierd.
Then, I ran a new wire from the lamp cluster to earth. Turned on lights and they worked....for a couple of minutes, then went out again with the return of the fault light. I have done a comparison between the faulty lamp cluster and the working one, checking resistances between the earth bus and van body and across the bulbs. All checks out the same to within 0.3ohm so this has got me a bit stumped.
Any help would be gratefully received.
Check all the other bulbs in the clusters - fog, reversing, maybe number plate.
Electrical contact cleaner is very good too - liberal spray
@BaronVonP7 help me understand why I would need to do that? As far as I know only the side/tail lamps are on the canbus circuit. Could there be some kind of interaction?
Both sides should be on separate circuits. My guess would be a short to ground between the control module and the lamp unit.
Do you have trailer plug fitted?
Good shout on the tow bar.
Does sound like an earth issue. One thing has it had a repair or bump as 95%of the time you get wiring faults where someone's been mauling about in the loom.
Be careful with the no plate lights as IIRC they are off a contol module (not fusebox) and if you blow that it is hundreds of pounds (it is recommended to only use like for like bulbs for these)
@Autoelec short to ground is something I hadn't considered, could be it though. Tracing the wiring is gonna be a bugger.
No towbar electrics fitted and no bump as far as I know.
@falkirk-mark the side lights are off the control module and thats what I'm worried about.
@Autoelec just been thinking about what you said and how to check for it. If I used my multimeter to test for continuity between the lamp feed cables and earth, would that prove a short or would I get a reading anyway through the control module?
Does the van have the com2000 unit, fault with the switch?
@bensongd no idea which unit it has, wouldn't a switch fault affect lamps at both sides?
No tow bar electrics...still, check if there is a plug under the rear overhang thats got corroded. Iveco use similar electrics, on those there are plugs to joint the ladder chassis and body looms together than can get broken wires/corrosion, on Iveco they are on low down on the radiator support on the battery side, but the engine is rotated 90 degrees and the chassis is monocoque on Relays so who knows if it even has a joint in the loom.
A lot of psa cars from the early 00s onwards use a shared unit for lights, indicators, wipers, cruise control air bags etc. On mine everything except the wash wipe worked, the switch had slipped out the housing. They are prone to indicator and lighting issues. With you mentioning the side lights come on with the headlights wondered if it might be the switch.
Yeah, you need to disconnect the control module and the lamp then check the circuits for isolation from ground. Always best to connect the negative lead of the meter at the battery negative, not a ground point or body / chassis panel.
@Autoelec just seen this after having another poke around this morning. So, I didn't disconnect the control module but checking from the rear lamp connectors on both the good and bad sides, there was no continuity between the live feeds and body earth. I don't think I have a lead long enough to reach battery earth from the back of the van. However, at the front I decided to compare both of the front side lamps. With the neg lead onto the jump start earth point. Good 0.2Ohm continuity on the neg side. The pos side had continuity at 3.8Ohm on both lamp connectors, I guess this was showing resistance through the control module? Would you expect a short to show a much lower resistance?
Now here's a new development. Since the fault light came on I have neither front or rear side lamps on the drivers side so I had assumed that the canbus turned both lamps off if it detected a fault. Passenger side has been working fine so far until I had the front bulb out on that side. After I put it back in at the front it stopped working. Maybe I haven't got it in right or have damaged it but the funny thing is that the rear side lamp is still working on that side which disproves what I had previously assumed and maybe gives another clue?