Brake light problem - BMW Forum

Dragoon · 04-18-2012, 01:38 PM

Hey Guys/Gals,

My 98 318i has a brake light problem. The brake lamps, (all three) do not illuminate when depressing the brake pedal. The lamps are freshly replaced last week and worked then and the fuse is good. Checked them again today and they look fine, no broken filaments.

What am I missing?

The head lights, high beams, fog lights, turn signals, parking lights, and back up lights, all work.

Any ideas or experience with a similar problem?

Thanks for any guidance you can offer.

Dragoon

Jack Dabsy · 04-18-2012, 01:41 PM

Either the pedal-switch or a wiring/connector fault at the rear-cluster.

Lord Vader · 04-18-2012, 04:06 PM

The bulbs are okay, but how is the lamp socket? The black thing the lamp plugs into which then goes into the light housing. I had one become loose and as a result te lights wouldn't light up. I replaced it for $17 at the dealership and it's fine now. Try that first.

Dragoon · 04-19-2012, 01:24 AM

In fact I do have one black plastic lamp holder with a piece of metal tab missing.

That would cause all three brake lamps not to illuminate?

Simple enough fix if that is the problem.

Thanks, I'll check it out. That and a brake pedal switch too.

Thanks again to both of you for the help.

Dragoon, the BMW Rookie.

Lord Vader · 04-19-2012, 02:46 AM

Worth a shot. Might not cause all 3 to go out but it's a decent option. Check the wiring loom that runs into the trunk. It's been known to fray and short out over time.

Dragoon · 04-19-2012, 09:09 AM

I moved lamp sockets, from one socket port to another, around to see if I can just get the brake lamps to light up with no positive results yet. In other words I used the back up light lamp socket, since it is identical and made for 21 watts, and put it into the brake light socket. No illumination.

Apparently it was a freak incident when I put in new brake lamps and they worked.

I guess that leaves me with inspecting wiring in the trunk section.

Thanks again and I'll keep looking and posting my results.

Dragoon · 04-20-2012, 12:11 AM

Hi, I did find one wire in the harness which goes into the trunk lid that had broken insulation. The other wires looked good. I repaired the broken insulation and put that particular section back together. Kept looking and as yet found nothing.

The effort continues.

By the way, I have been reading the posts concerning the other electrical problems folks have been having with their BMW's.

Thanks.

Lord Vader · 04-20-2012, 01:26 AM

Their ate unfortunately numerous electrical issues that can crop up. The trunk wiring is a common one. The one that I despise right now is the door actuators and central central locking system. My locks arent working properly and diagnosing it can be a pain since you have to take the door panels off to get to the actuator.

Dragoon · 04-20-2012, 06:36 PM

LV, right now I am at a loss as to where the problem lies. Dabsy's suggestion of checking out the brake switch at the pedal is the best idea now and my next step. To the best of my knowledge everything else has been eliminated. It is frustrating to attempt inspecting wiring when a person has to ruin plastic fasteners that holds the plastic trim so one can see if there is any deteriorated insulation of the wiring. Not to mention the risk of breaking the trim.

But, it is a 14 year old car and a person always has to do to some maintenance to get a used vehicle up to speed.

The effort continues.

Thanks LV and Dabsy.

Dragoon

Dragoon · 04-21-2012, 10:57 PM

The non-illuminating brake lamps continue to be a problem. I have power to the switch. The switch continuity checks out good as per page 600-5 in "my" down-loaded Bentley's service manual. I tried to remove the brake switch from the pedal bracket and was unable too. If continuity is good then right now I see no need to remove it anyway.

Am I missing something?

I forgot Dabsy mentioned the wiring connectors at the light housing. So I will have to check that soon.

Am I back to the lamp sockets?

Dragoon

Lord Vader · 04-21-2012, 11:27 PM

Well of the third brake light isn't lighting up either then it's probably more then the lamp sockets. Unfortunately. The third brake light can still light up even if both tail lights are burned out.

Dragoon · 04-22-2012, 06:19 AM

Thanks L.V.

Knowing electricity is or can be a strange animal I nonetheless assume that an unblown fuse means the wiring is not shorting out, therefore good. Lamps are good. Switch appears to be good. Power to the switch is good.

I need to recruit a helper to assist in checking power to the connectors at the housing. Doing this by myself stretches a guy a little thin when trying to reach a pedal and connectors in the trunk.

As mentioned earlier, I am back to either the connectors or the lamp sockets.

The Effort continues.

Thanks again.

Dragoon

Jack Dabsy · 04-22-2012, 09:14 AM

Bad earth/ground it is then... Check the fragile earthing-blocks bolted to the flimsy bodywork !!

Dragoon · 04-22-2012, 04:36 PM

Thanks J.D.

Nothing like overlooking the obvious, huh? Positive proof I am not an electrican.

Oh and I found a helper. A five pound block of wood to hold down the brake pedal.

Well, back at it.

Thanks again.

Dragoon

bgnotch · 04-23-2012, 03:08 AM

Try putting a testlamp in the fuse socket to see if there is power at the fuse block. And if you are using the Original BMW fuses the kind with the little wire, those break a very thin break. They appear good so make sure to tug on the little wire to make sure its still good.