Rear near side brake light fault

Dear all, Thanks in advance for any light you may be able to shed on this little fault. I noticed yesterday that my rear nearside brake light was out and thought this would be an easy fix. When I removed the old bulb it had clearly blown. However, after replacing it yesterday it still won't work. When I turn my main lights on the bulb lights up as per normal so clearly it is getting a power supply. However, when I depress the brake pedal the brake light filament glows red without coming on fully. I have tried several other bulbs of different makes and still get the same result. The spoiler brake light and offside light are both working normally. Any ideas on a solution would be much appreciated. Kind regards Gerry

Hi Garry As that side rear light works ok that would prove the earth is ok, make sure that the connection in the bulb holder is nice and clean, If that’s ok It can only be that you have a localised doggie connection reducing the voltage, a multimeter voltage check should prove this. Best of luck. Andy

Cheers Andy, Thanks for your advice which I appreciate. I did clean up the contacts with a bit of sandpaper in case it was a dodgy connection. I will have a look with a meter tomorrow and see what I can find and report back. I'm relieved that it isn't an earthing problem. Cheers Gerry

See below link to wiring schematics see sheet one http://arma.free.fr/porsc...Wiring%201999-2000.pdf

I think it sounds more like a bad earth. The centre and offside brake lights have different ground wires, so could be working normally with the nearside being dim. The lights within the light cluster share a common earth. Are the side light, reversing light, and indicator light dim on that side?

Hi Richard That's what i thought at first but he said the side light is fine. be interesting to know the result though. Andy

Gents, I can confirm that the side lights and reverse lights are working fine. I haven't used my meter yet as I have come into work today but will tamper with it later and let you know what I find. Cheers Gerry

Silly question but will the light unit plug in the other side That way you can tell if its a Unit fault or an earthing fault Obviously you cant install it the wrong way

Now why didn't I think of doing that! That's a great idea that may easily expose the source of the problem. Thanks. I'm at Brands Hatch tomorrow and hope to get it fixed by then. Cheers Gerry

So many people look at too serious a problem Remember when I had a quattro the ECU was always blamed. But my specialist says always at the cheapest fix first I had just fixed a problem with the exhaust manifold Horrible job but got it all back together again Just could not get the power in so called technical adviser said it was the ECU< Another guy who helped me buy the car spend 2 hours checking everything gave up when along comes Malcolm and we start at the Fuse Box ( Fuses are 10 a penny) On the quattro there are 5 extra fuses that run down the side of the box - very Heath Robinson - sure enough on of the fuses was not in properly - JOB DONE and she fired up and ran like a dream!!

Hi Richard, I've checked the fuses and didn't find a problem so it's not the fuse although I do agree to start checking the little things before throwing more you at the bigger stuff. I didn't get a chance to look at it yesterday. I got home late from work and we had a cracking storm, thunder, lightning and hailstones. Anyhow, I'm at Brands Hatch today with the Kent region so won't get a chance to delve deeper for a day or so. Cheers Gerry

Not sure if you can see this at Brands But maybe borrow a light unit from another car!!

Not sure if this helps Similar problem on a 987 (Facebook page!!??!!) Apparently Water can get under the Driver's seat and cause corrosion (Not sure if Right or left hand drive makes a difference) There is something there that can cause your problem Strange though Just see if its wet - may need to check both sides as I don't know which side the unit is on , on RHD Cars

Dry as a bone Richard but it's been parked in the sunshine all day. ?? I'll certainly check that area again though. Gerry

Hi all, Firstly a big thanks for all your assistance. I appreciate it. I finally got my meter on it tonight and traced the fault to the earth part on the bulb connector. I had already cleaned the two silver contacts that the bulb connected to but not the brass earth. A quick rub down with some emery paper to clean the contacts and it worked a treat. Strange thing was that when I turned the side lights on they worked normally but as soon as I touched the brake pedal the light went off. When I turned the side lights off and placed my foot on the brake the same filament glowed red without coming on fully so I traced it quite quickly in the end. Thanks once again Gerry

Glad its sorted Nice cheap fix !! Its strange how a bad earth throws up strange Quite often a blown filament in a twin bulb can cause a short and turn other lights on Richard