On my 2005 S40 the interior lights seem to be acting strange. When a door is opened only the footwell lights illuminate. None of the front or rear reading lights (aka map lights) in the overhead panels will light up. This is with the 3 position switch on the front overhead light panel in any position.

Now the overhead reading lights themselves do strange things once you are inside the car with the doors closed. Pressing a single side switch will illuminate that side reading light to bright. However, pressing the other side's switch will cause both lights to illuminate but only very dim. Now pressing a rear reading light causes the all reading lights to completely go dark.

The overhead lights are acting as if there is a limited amount of wattage and that everytime I turn on another light the wattage is divided between the working lights. If I turn on enough lights they all go dark as there is not enough watts to run them all.

Any ideas where I should start looking? The fuses checked good. Is there something common these lights share?

 

Good read... Thanks for passing it along.

 

Im having the same problem. Did you find a solution to this problem?

 

Yes, I had a blown fuse in the interior fuse panel. While looking for another issue I pulled every single fuse until I found one that was blown. Once replaced the interior lights magically worked correctly. I don't remember which fuse though because it was not one of the interior light fuses.

 

That was it. It was fuse #47: Moonroof; door mirrors
Everything works well now. Thanks for the help.

 

Almost three and a half years later and this thread still helped! I was going crazy trying to find the issue.

Thanks all for the thread!!

Thanks admins for a great site for flying boxes!

 

Thanks Hudini, your post was so useful. I had a same issue & got fix with replace the F47 (5A fuse) very inexpensive and wasn't difficult to replace it. Feel magical.

 

i have the same issue, F47 blows when being replaced with a new fuse, all the interior lights do have power, has anyone located what other fuse could be working in conjunction with F47, all my other fuses in the car and in the engine bay are good??

 

I'm having the same issue with F47 blowing each time I replace it. Just starting troubleshooting interior light problems for a friend's car and ran into this fuse. The rear interior reading lights do not work. So far, all other interior lights are working from what I can see. Now just waiting for advice on here to troubleshoot it further.

 

Just substitute a leaded light bulb for the fuse. Ideally, the wires will be long enough that you can place the light bulb where you can see it from anywhere in the car. Also, try to use a lamp that's pretty bright - 20-30 watts would be good (think tail light or even a headlight bulb should work).

Now, instead of blowing a fuse, the "test light" will light up - most likely pretty brightly if there's a hard short to ground on the power side of the light circuit, but the "test light" being in series will limit the current to well under what the circuit is designed for. Now, just start pulling plugs / bulbs / connectors on the associated lights in the interior until your "test light" goes much dimmer (it will still glow once the short circuit is removed, and the lights won't be as bright as they should be, since the "test bulb" is dropping the voltage that's available to them).

You could also remove the fuse, and (being carful about which side is hot, and which isn't), connect an ohmmeter from the LOAD SIDE (without voltage) to ground. If fuse F47 is a 10 amp fuse, figure that any resistance LOWER than 1.2 ohms will mean that the fuse would blow. As above, remove plugs / bulbs / connectors until your ohmmeter reads "normal" (I'm guessing 3-5 ohms with most of the lights in the on position).

 

This was so useful didnt even think you could have a blown fuse and your lights keep working, although not in sequence. Yes my F47 fuse blown!

 

This is very good info to keep in mind.

had a similar symptom after recovering my headliner panel and reinstalling. It turned out that I had pinch one of the wires at the passenger side front door under the headliner bracket. I believe it was a ground wire which caused a sneak path and the lights were behaving very similar to what was stated above.

 

Who would have thought that replacing a fuse that's for the sunroof / mirrors on the doors what effect the lights on the interior. The fuse location is under the glove box, top row, 5th fuse down. And as everybody has said it's a 5 amp fuse. Thanks everybody for the info! You guys save me a lot of headaches!

 

I'm surprised I didn't have this fuse issue years ago. My lights started acting funny (although still on to some degree) as well after replacing the headliner. Thanks for the advise on this!
I was debating weather to replace the headliner as it was starting to fall in the corners, until my car took on A LOT of water due to the front driver side sunroof drain pipe pulling out of the fitting right where the firewall, windshield and dash all come together. Since the front carpet tub has a couple inches of foam underneath, I din't notice the water collecting until I checked the back floorboard one day. So out came the carpet, headliner and front windshield (makes the headliner removal real easy), re-covered the headliner, replaced the hoses and dried out the car. All better now.