Help - blown bulb issue

[Mr-B]

Bit of background - 2004 e46 coupe, out in the car about a week ago in dense fog so used the foglights for the first time in years. Used the car since with no lights during the day and normal lights at night without the fogs on, no issues. Got in the car yesterday and blown bulb warning on the dash and walking round the car can see no rear foglight working and one front fog not working, all other lights OK. Swapped the rear fog light bulb with a working one but it still won't light with the good bulb, haven't tried a working bulb in the front yet but as both lights went at the same time I'm thinking it must be linked and the front bulb is actually OK.

Anyone had this before? Is this a wiring issue? What could have been the cause since it seemed to appear overnight without reason. I am the only person that uses the car.

[Gesberg]

Just a thought, are both rear fog lamps actually connected? I have a vague memory that only the rear offside was connected on one my E46s.
Ah, sorry read again, see it was working before.
Was also a thing that wire in the connector to the boot lid split, may be worth sliding the rubber cover out of the way and checking the cables.

Edited by Gesberg on Sunday 2nd January 13:26

[Mr-B]

Yes it has only one working light by design, the other bulb is not present and a blank plate covering the bulb socket. The wiring looks to be OK after a cursory glance but I don't have any electrical resting equipment to check the integrity of it. The reversing light in the same unit is working OK and I used that bulb to check the foglight socket.

[RUSSELLM]

You could do with a cheap multimeter really.

Failing that, it’s a case of checking the fuses and relays (if fitted)

Only other thing I could think of, is if the Two fog lamps on one side of the car, are wired in series. So one blown lamp would make the other fail. Can’t imagine a car manufacturer doing that though

[Mr-B]

The strange thing is the rear fog light isn't working (drivers side obvs) and the front passenger side front fog isn't either. I also spotted water inside the boot yesterday and in all the many years I have had the car the boot has been bone dry, maybe coincidence, maybe not, maybe water was in there before and I just hadn't noticed it.

[Mr-B]

A poster mentioned relays, do this generation of BMW have relays for foglights? If so where would they be located?

I have found there is quite a bit of damp in the boot, not sure how as the rubber seals look to be in decent condition, not brittle and no chunks missing or creases in them. (some research shows it could be the rear windscreen seal which is leaking, or light seals or antenna seal) but has the water ingress done damage to a relay??

Had a look at the fuse box and there is only one fuse that specifically states front foglight and that is OK but one front fog light isn't working (haven't had a look at that bulb yet), there is no separate fuse for rear foglight but there is for reversing light which is part of the same light unit on the bootlid and that fuse is OK and the reversing lights work.

[Mr-B]

Noticed the engine turning over a bit slower than normal recently, mainly due to a lot of small local trips not recharging the battery and the very cold nights we have been having, so trickle charged it overnight and this morning the warning light on the dash wasn't on and the rear fog was working (but not the front). Weird. I didn't think this era of BMW's were sophisticated enough to be upset by a low battery? It's had a low battery in the past but it's never thrown a warning light of any kind. Best check the front bulb as I haven't done that yet.

[Elliot2000]

I’m not sure, but I think the front dogs are not monitored the e46. When the bulb warning was on it should show what area of the car it’s detecting the fault- depending where the warning lights is on in relation to the picture of the car .

I’d imagine you have a bad connection in the boot and it’s just managing to make a connection for now rather than the battery charge causing the issue. Check the plug connections to each of the rear bulb holders and peel back the corrugate rubber tubing covering the loom as it goes into the boot lid

[Mr-B]

Elliot2000 said:

I’m not sure, but I think the front dogs are not monitored the e46. When the bulb warning was on it should show what area of the car it’s detecting the fault- depending where the warning lights is on in relation to the picture of the car .

I’d imagine you have a bad connection in the boot and it’s just managing to make a connection for now rather than the battery charge causing the issue. Check the plug connections to each of the rear bulb holders and peel back the corrugate rubber tubing covering the loom as it goes into the boot lid

I think the problem is connected to damp/condensation. The dry weather we had recently gave the car a chance to rid itself of moisture and the warning light went away and the bulb was working, got in the car a few days ago and noticed a lot of condensation in the car and the warning light/dead bulb were back. Not sure where the water is getting in (boot seal looks OK) and the boot is a lot drier than a few weeks back when it was very damp.