A while ago, a car parked behind mine decided to spontaneously combust, melting my rear bumper and the outsides of the light clusters, plus scorching the hatchback.

The light bulbs themselves weren't damaged and still worked, as did my aftermarket reversing sensor system, none of the wires were melted.

I got a garage to replace the bumper, hatchback and light plastics, but I'm having a problem with the "faulty light" detector as, whenever I turn on the lights, the bulb symbol on the instrument panel comes on.

All the bulbs work, I've taken them out, cleaned the contacts, tried disconnecting the reversing sensors etc, but I'm still getting the warning light.

I don't know what else I can do to sort this out, the MOT is coming up in a couple of months and, despite the functioning lights, I'm worried that the presence of the warning light will result in a fail.

Can anyone offer any suggestions as to what I can do next?

If you have a place where you usually take your cars for MOT, I would pop in and ask them.

I suspect that if all lights (including number plate lights?) are OK, that the warning light cannot constitute a reason for failure.

I believe that the 'common wisdom' that 'any warning light is a fail' is simply an urban myth.

Maybe one or some of the new bulbs are not the exact/correct power/wattage.

One other thing, if you had bought this car used, maybe, just maybe, previous owner had swopped some filament bulbs for LED versions, and made changes in the car's BCM coding so that the "faulty light" warning then did not come on, and now that the rear clusters have been replaced, the bulbs currently fitted will now be back to being filament bulbs.

You'd need to get someone to check the coding for the lights to work that one out.

2 hours ago, Breezy_Pete said:

I suspect that if all lights (including number plate lights?) are OK, that the warning light cannot constitute a reason for failure.

I believe that the 'common wisdom' that 'any warning light is a fail' is simply an urban myth.

Thanks for the reply.

I've looked at a bunch of sites and it seems that it's only a Red warning lights that are automatic fails, Amber ones may not, depending on what they are.

But, yes, all the lights, including the number plate lights, are working OK.

I'll give my MOT place a call on Monday and see what they say.

Had it on on my Octavia with no blown bulbs. Had a bit of corosion on number plate lights and when cleaned up light went off.

Alasdair

1 hour ago, rum4mo said:

Maybe one or some of the new bulbs are not the exact/correct power/wattage.

All the lights are incandescent, not LED and I wasn't getting the problem before the fire.

As far as I know, apart from the numberplate lights, the garage re-used the bulbs from before.

I found this video which suggests actually checking the bulbs themselves and maybe the number plate bulbs are the wrong wattage, I'll have a look.

https://youtu.be/JJeRxRi7Lpo?si=VUB2mziqUXTN0BAb

1 minute ago, Alasdair1 said:

Had it on on my Octavia with no blown bulbs. Had a bit of corosion on number plate lights and when cleaned up light went off.

I cleaned up all the contacts on the tail lights, but not the number plate lights, so I'll take a look at those, thanks.

I checked the number plate lights and squirted some contact cleaner on them and they seemed OK.

One thing which I didn't think of before, was to turn the light switch to side lights instead of just all on and found that I still got the warning, even though they're all working.

The side lights did seem to be a mix of types, so, out of frustration I swapped all the side light bulbs (rear and front) for new 12v W5W T10 bulbs, but that didn't help either :(

So I really have no idea what is going on...

Look at the connector contacts on both sides. I mean the loom connector which plugs into the whole light cluster.

You're looking for crusty corrosion, especially on the contacts of the brown earth wire both sides.

Look at the male pins on the light cluster connectors too.

Edited 20 June20 Jun by Breezy_Pete

16 minutes ago, Breezy_Pete said:

Look at the connector contacts on both sides. I mean the loom connector which plugs into the whole light cluster.

You're looking for crusty corrosion, especially on the contacts of the brown earth wire both sides.

Look at the male pins on the light cluster connectors too.

I did check those and they seemed OK, but I squirted some contact cleaner onto them too.

I might have another look tomorrow and give them a go-over with some emery paper just in case I missed something.