Troubleshooting for sidelights/rear lights not working

[ericgreveson]

Hello! On the way back from a trip to the drive-in cinema at the weekend, it turned out that while the main beam headlights and brake lights are working fine, the sidelights (and rear lights) are not... first time it's been out in the dark for a while! I've been trying to figure out what's wrong but can't work it out yet and am hoping someone might have some ideas of what to check next. Symptoms:
- When turning the headlight switch to the first position, the sidelamp relay on the fusebox (circled in blue) clicks, and the backlights on the pod come on, but none of the external lights come on (front or back)
- When turning the headlight switch to the second position, I can feel/hear at least two relays click on the fusebox: seems like the sidelamp relay and the dip beam relay. The headlights then come on but the sidelamps and rear lights remain off.
- All other lights seem to work as normal (indicators, brakes, reverse light etc).
- I have checked the green-circled fuses are all fine.



I know this has been covered in some detail before and have read the below threads...
https://www.pistonheads.com/gassing/topic.asp?t=90...
https://www.pistonheads.com/gassing/topic.asp?t=92...
https://www.pistonheads.com/gassing/topic.asp?t=10...
https://www.pistonheads.com/gassing/topic.asp?t=16...

...but now I'm stuck! Car is a 2003 Tuscan S with the HID lamps if that makes any difference. Some things that might help if anyone knows:
- Relays on the pod itself are mentioned as a potential issue. Is it possible for that to not be working but the sidelamps relay on the fusebox to still be working? (I'm hoping not since it seems like it might be a pain to fix anything on the pod circuit boards...)
- Is there a wiring diagram or similar that shows what is "downstream" of the fusebox relay?
- presumably if a bulb was gone, it wouldn't mean all the lights go out? So it shouldn't be that.
- could be a bad connection of course - but which wires do I need to check?

Any advice appreciated... also I'll update this thread if I figure out what the problem was!

[Gladers01]

ericgreveson said:

Hello! On the way back from a trip to the drive-in cinema at the weekend, it turned out that while the main beam headlights and brake lights are working fine, the sidelights (and rear lights) are not... first time it's been out in the dark for a while! I've been trying to figure out what's wrong but can't work it out yet and am hoping someone might have some ideas of what to check next. Symptoms:
- When turning the headlight switch to the first position, the sidelamp relay on the fusebox (circled in blue) clicks, and the backlights on the pod come on, but none of the external lights come on (front or back)
- When turning the headlight switch to the second position, I can feel/hear at least two relays click on the fusebox: seems like the sidelamp relay and the dip beam relay. The headlights then come on but the sidelamps and rear lights remain off.
- All other lights seem to work as normal (indicators, brakes, reverse light etc).
- I have checked the green-circled fuses are all fine.



I know this has been covered in some detail before and have read the below threads...
https://www.pistonheads.com/gassing/topic.asp?t=90...
https://www.pistonheads.com/gassing/topic.asp?t=92...
https://www.pistonheads.com/gassing/topic.asp?t=10...
https://www.pistonheads.com/gassing/topic.asp?t=16...

...but now I'm stuck! Car is a 2003 Tuscan S with the HID lamps if that makes any difference. Some things that might help if anyone knows:
- Relays on the pod itself are mentioned as a potential issue. Is it possible for that to not be working but the sidelamps relay on the fusebox to still be working? (I'm hoping not since it seems like it might be a pain to fix anything on the pod circuit boards...)
- Is there a wiring diagram or similar that shows what is "downstream" of the fusebox relay?
- presumably if a bulb was gone, it wouldn't mean all the lights go out? So it shouldn't be that.
- could be a bad connection of course - but which wires do I need to check?

Any advice appreciated... also I'll update this thread if I figure out what the problem was!

Try tapping the sidelight relay with the light switch at position 1, it's a good sign you can hear the relay energise but the contacts may be pitted or at a high resistance, failing that swop the sidelight relay with the one from the low beam relay (no.52 yellow) see if that makes any difference, the problem is common to all bulbs so assuming all the fuses are intact it will be a single point of failure somewhere.

If the bulb/s blow in such a way to become a short circuit (rather than open) the fuse/s should blow to protect the circuit.

Good luck, post back later if you have any more info

[Penelope Stopit]

PM sent

[ericgreveson]

Thanks! Indeed it is the sidelights relay, it makes a noise but doesn't conduct - swapping with the dip beam relay proved it. Don't know why I didn't think of trying that! Nice easy fix - new relay needed.

[Gladers01]

ericgreveson said:

Thanks! Indeed it is the sidelights relay, it makes a noise but doesn't conduct - swapping with the dip beam relay proved it. Don't know why I didn't think of trying that! Nice easy fix - new relay needed.

Good work! Not seen one fail before, the relay is a M0643 and is pretty common, i use Racetech for parts as they are local to me, other suppliers are widely available of course.

The other thing you can do there is to buy a spare relay and fit it to one of the spare relay sockets 11,12 or 13 near to the spare fuses, to be on the safe side

[ericgreveson]

Yep, ordered a couple off eBay - one for a replacement, one for a spare! I opened up the faulty relay and it looked like there was corrosion or some similar powdered metal on the outside of the coil that was bridging across to some other contacts - I guess it's 17 years old now so not too surprising really!

[Penelope Stopit]

Are there any signs of moisture stains along the bottom of the fuse-box?

It might be worth pulling out and opening up any relays that will open and take a good look at them

Reasoning being that there is a possibility of corrosion within the fuse-box

[ericgreveson]

Indeed, good points to check - actually the fusebox was replaced about 2 years ago due to corrosion, so it's possible that this relay was already on its way out then... all maybe due to a slightly leaky door seal years ago when the car was parked outside without a cover, a bit of moisture in the driver's footwell would have done the trick over an ~8 year period!