[Non Corsa] Stupid Mercedes and their stupid tail lights

[jt999]

My tail light (only 1) is intermittent, most of the time it's not working but whenever I go to change the bulb it is. I've now changed the bulb 4 times (the final time was a different brand, rather than Halfords own).

Any ideas what it could be? Am I safe to plug/unplug a bulb with the lights on? I'd like to test the circuit and then put a bulb in without turning the lights off/on so I know it hasn't reset anything.

[Taurus]

Sounds like a bad contact - you should be able to plug a bulb in with the lights on, if you think about it then it's only doing the same thing as an intermittently working bulb that makes and breaks contact. The book probably says you shouldn't, but rules are only for the guidance of the wise. Check for any signs of corrosion on the contacts and maybe try cleaning them, either very light abrasive (very very light) or switch cleaner. But don't get switch cleaner on live circuit boards - you will be very sad if you do 'cos it breaks them.

[jt999]

Cheers Taurus, will have a look. Didn't seem to be any corrosion that I could see (I wondered about that in the first place).

I'll see if I can clean the contacts, if it keeps doing it I'll just book it in, it's all under warranty I assume

[Bugman]

Some bulb holders rely on a fairly crude springy bar for the bottom contact. If this is adjusted too deep the centre contact on the bulb may not be reaching it. If design and warranty allow you may be able to improve the contact by gently prising it up slightly with something non conductive

If its not adjustable you could try modifying the bulb by adding an extra blob of solder on the centre contact. This bodge is maybe more suited to aging corsas!

[jt999]

It's a 955 (I think) - the push fit bulb so there is no centre contact, thanks though. Weather was too nice to bother today, maybe tomorrow!

[Bugman]

Ah. I have another cunning plan. If its a conventional tungsten capless rather than an led you could try prising the exposed contact wires out slightly.But be careful,the wires break easily.

[walksall]

Is it a 'standard' (old fashioned) wiring system, or is it a CAN bus? If it's the latter, you can get all sorts of strange things happen, so - if it's under warranty, I'd let 'them' sort it.

Regards

[jt999]

Stupid Mercedes and their stupid tail lights

Got the multimeter out again today. It's very odd, I could see about 9v and then suddenly it was gone, so it's something deeper, I'm going to check the fuses (when I can find them) and then book it into Mercedes if there is no change.

I've got no idea what sort of wiring but no doubt it's the more complicated of the two.

[Vegas]

You should not go near the wiring

[jt999]

You should not go near the wiring

I'd only be changing a fuse! Plus... It all worked, what more can you ask for?

[Taurus]

I hope it isn't an electrical gremlin - I've known too many people have random electrical issues with them which the dealerships can't get to the bottom of. Worst one was total electrical failure at night on a motorway which left the car stranded across the middle & outer lane with the driver locked in it. Fortunately a police Range Rover was minutes away and just hauled it off the carriageway. The dealership had it for months, even replaced the whole loom - two weeks later it did it again.

Low voltage then disappearing can be a bad contact - that would a good outcome.

[jt999]

Well I do hope that doesn't occur

[jt999]

I've booked it in with Mercedes as I got annoyed with it, hopefully it's covered by warranty

[Taurus]

There was a bloke on telly last Sunday who works for Mercedes, Lewis something or other, seemed like a decent guy. Maybe he'll be working on it.

[jt999]

He didn't look like he knew the intricacies of the A Class wiring though, I guess I'll find out next week!