2004 Megane headlights staying on!

the car is parked with the keys out.

work initially, but the fault reoccurred latter. This may have been coincidental.

did this last night.

fault had gone - only for the fault to reappear a couple of hours later, whist the car had been parked.

Faulty relay?

Not of direct help to you, but for future reference it is not a good idea to use WD40 on electrical contacts. It is primarily a (W)ater (D)ispersant, and hence oily. It may create more problems than it solves.

To clean electrical contacts, use an electrical contact cleaner such as Servisol 10.

Not really; it's a Megane... ;-)

Chris

I must admit, that did cross my mind. I was having a look earlier today. There are two near the fusebox inside the car, is one of those likely to be the headlight one. These relays seem a bit hard to get too - but I can just get my hand in the recess. Do they pull out of the socket?

TIA

Thanks - I will get some...

the headlight one.

recess. Do they pull out of the socket?

Probably; but I havn't had a French car for at least 15 years, and that was ten years old. Hopefully someone else will know!

I believe that this model has a CPU that controls lots of things including lights, and if you have discharge lights then even more complication. other than checking all connections and earth points and inspecting for water ingress there is probably not really a lot you can do except ask an expert to look.

Does it have a 'path lighting' function when you lock the car - to find your way to the house etc in the dark?

Yep, that kinda makes sense. I'm now noticing odd behavior with the lights= .

I disconnected the battery last night and low and behold, this morning, onc= e I'd put the battery back on, the car is fine. Well, almost - with engine= off, flashing the high beam make the main beam come on and stay on. Once = the engine starts, everything is fine, and the main beam goes off.

It has rained heavy up here in the north east, and it was only a day or so = since these symptoms started.

I think the nest thing is to check for water ingress... Is is going to be = ok to stray wd40 on the the fuse box under the bonnet - or should I use som= ething else? =20

TIA

Not as far as I know. It not my car, its the girlfriends car, she only had it about 8 months - but never noticed that feature.

wd40 is made to displace moisture, so it should be fine. I expect that removing the battery connection is doing the equivalent of a hard reset and curing the problem for a while. Finding the cpu that controls everything might be the answer, if it is getting wet it could easily cause these faults, some vehicles are well known for water on the cpu, such as audi: after windscreen replacement (badly done) water dribbles down the bulkhead straight into the main lump with the millions of wires.

Yeah, it does have the feel of a PC problem. It is almost as if the car is powered by windows 95, and restarting solves the problem.

powered by windows 95, and restarting solves the problem.

ROFL!

Mate of my brother had exactly this on a 56 Modus. Sorry, don't know what caused it (and he's in NZ) but he referred to a "module" - his local garage wouldn't touch it and a Renault dealer in Cardiff fixed it quickly and efficiently.....................for £500 ish.

Cheers for the link. I won't spend 500 quid on the car, if needs be I'll keep disconnecting the battery for a temp fix, or, try to get a secondhand control unit off eBay.

The good thing is, at the moment as long as I disconnect the battery, the fault disappears.

Might be worth registering here?

then sell it in the dry weather.

Yep, after some trial and error, I'm now pretty sure its the UPC switching unit under the bonnet.

What I want to do now is take it off the car and dry it out indoors. I feel sure its water ingress in the unit.

A circuit diagram of the unit would be helpful - I have some experience of electronics to board level, so, although it is a long shot, I may be able to repair the fault.

unit under the bonnet.

sure its water ingress in the unit.

electronics to board level, so, although it is a long shot, I may be able to repair the fault.

Ok, so just after I posted I had another look. I think I've found the headlight relays under the UPC. The UPC is tricky to remove, but not impossible.

Just a follow up on this:

Took the car for a long drive with the headlight stuck on main beam (during the day as not to blind people too much), and miraculously, the headlights went off sometime into my trip.

I can only surmise the engine heat dried the UPC out.

I was going to take it off and dry it out inside the house, but the engine heat must have done it for me.

The battery has been connected for 24 hours now, and the light are as normal.

Fingers crossed.