Brake lamp warning

[Yogawrench]

One other thing to check... When reinstalling the knee bolster, make sure that none of the nearby wiring gets shoved into the brake light switch. I used a few zip ties to keep all wires from bumping into the brake switch. These brake switches sometimes do not fit snugly into the bracket and can cause problems.


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[Yogawrench]

I had a similar bedeviling problem with the brake warning light. I did the following:

1. Purchased new Osram brand brake light bulbs. This includes the 3rd brake light bulb.

2. Removed the brake light bulb carriers and examined the sockets and their contact points for possible poor fitment with the bulb. Used fine grade steel wool and a small screwdriver to remove any oxidation from all the socket contact points. The 3rd brake light carrier in particular had a small area for the bulb to touch the contact base,so I gently bent it to provide a wider surface of contact.

3. Before installing the new bulbs I put a small dab of bulb grease on the bulb bases. Made sure each bulb fitted snugly into its socket.

4. Removed the brake light check relay located next to the antenna unit in the trunk. Cleaned the relay pins with fine steel wool before reinstalling. Checked for a snug fit between relay and wiring plugs.

5. Removed the driver's side knee bolster to inspect the brake light switch on the brake pedal. Sprayed the switch plunger with an aerosol graphite spray to make sure it was not sticking.

The brake warning light now goes out correctly once the car is started and I apply the brake pedal. I believe my problem was a combination of non-Osram brand bulbs and a poor fitment of bulb and socket in the 3rd brake light. The connection of bulb and 3rd brake light socket base was minimal that it frequently triggered a fault when driving over a rough or bumpy road.



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[jswest69]

Wow, lots of input. Thanks and still working on it. If I fugure it out I will post what I finally found.

[McGyver]

well good luck! the check circuit may not be the issue, but at least you'll know for sure and it only takes a few minutes to get to it.

[Semblance]

Oh ok, it's inside the body. I'll take a look next time I have it open. Mine is a 89 also.

[McGyver]

So if I remove my rear seats, and remove the interior black panel so I'm looking at bare metal, there's nothing there. Is it actually inside the body, or am I looking in the wrong place?

i have a 1989 325i convertible, so unless your vert is different, you will need to remove the rear seat and the interior panel on the driver's side. The little circuit/relay thing will be in the cavity somewhere behind or below the speaker inside the body panel.

[Semblance]

You're talking about something else. And as i said, the check panel circuit/relay/boxy-thing is not behind the seat, it's behind the side panel in the back on the driver's side. (as opposed to next to the antenna on a coupe) This panel may have a bad connection or be broken and causing the check panel to light up.

So if I remove my rear seats, and remove the interior black panel so I'm looking at bare metal, there's nothing there. Is it actually inside the body, or am I looking in the wrong place?

[jlevie]

The logic of the brake warning light is the AND of power to the circuit and all three current sensors. If the result is true, the LED turns off. If false it turns on. The power up state of the logic is for the LED to be on, which is why you have to step on the brake after starting the car.

Since the OP stated that the right turn signal can activate the warning, the only logical explanation is a wiring problem that is allowing at least some power to reach the brake circuit. If that leakage is insufficient to allow full current flow, the LED will turn on.

[Liquidity]

Try new bulbs too, everywhere. Had this problem, replacing the third brake light bulb,which was working, fixed the problem.

If replacing a working bulb fixes a problem the problem was a loose connection but most of these problems come from using the wrong type of bulb from the start. The base has to be the correct metal or else it will galvanize against the socket. Multiple bulbs will fit the same socket but only the one with the right metal base won't galvanize. Something else you can do to prevent the corrosion is put some dielectric silicone on the bulb before you put it in.

[McGyver]

No, on verts it's not behind the seat, it's in the third brake light, which he's already bypassed. Dunno man, check your grounds? Try to find Luke's thread as FLG suggested, he talks about cleaning the ground connection inside the tail bulb holder. When I was tracking mine down, I actually couldn't clean mine, i couldn't pull the connectors apart, but maybe it will be easier on yours.

You're talking about something else. And as i said, the check panel circuit/relay/boxy-thing is not behind the seat, it's behind the side panel in the back on the driver's side. (as opposed to next to the antenna on a coupe) This panel may have a bad connection or be broken and causing the check panel to light up.

[Semblance]

No, on verts it's not behind the seat, it's in the third brake light, which he's already bypassed. Dunno man, check your grounds? Try to find Luke's thread as FLG suggested, he talks about cleaning the ground connection inside the tail bulb holder. When I was tracking mine down, I actually couldn't clean mine, i couldn't pull the connectors apart, but maybe it will be easier on yours.

[McGyver]

The Check Circuit that was mentioned will be mounted behind the rear seat side panel on the drivers side. check to make sure all of the wires are clipped in properly, and maybe ziptie the plugs in.

[FLG]

I remember German audio specialties (forgot his name on here) has a post somewhere about cleaning something.. Perhaps it's on the board itself, I can't remember exactly but do a search and I'm sure u can dig it up

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[jswest69]

New brake switch didn't work either. It is a mystery...

[jswest69]

All new bulbs already, cleaned every socket and connection, eliminated the third brake light check circuit. Will try a new brake light switch. Thanks for all the suggestions.