Brake Warning Light 1981 911 SC Targa

[jmeany]

I JUST got my new to me toy. YEAH!!! But.... I had the warning light show up the other morning and soo back home to the garage it went. I checked out for leaking hoses and fluid levels going down in the master cylinder, and the E-Brake switch all seems to be fine. But alas... Light still lit. Any suggestions?



JMeany
1955 300SL Gullwing (My Dad's Gone so dont' ask..)
1981 911SCTarga
2005 PT Rag
2003 Hyundia Santa Fe
1991 Miata

[jmeany]

Opps! Oh Yeah it has a recent brake job on all four, New Rotors, calipers pads, ect...

[emcon5]

The brake warning light comes on when the parking brake is on, or if there is a (percieved) problem with the brake system.

There are 2 pressure operated brake light switches on the Master Cylinder, one for the front circuit, one for the rear. The are wired so that if the position of the two switches does not agree, (both open or both closed) the logic in the light assumes one of the brake circuits has failed, and turns on the warning light.

If your brakes are in good shape, and properly maintained, the problem is usually one of the switches has become gummed up with old nasty brake fluid, and either doesn't work, or works slower than the other. The switches are inexpensive, and fairly easy to swap, but you must disconnect the battery to reset the light.

Hope this helps,

Tom

[ErVikingo]

If that doesn't help, change the transmission ground strap.

A faulty strap could casue your emergency brake light to activate also (amongst other problems; damages to the clutch cable, dim lights, ...). Im talking from experience here, I had that problem and Bruce Anderson suggested this fix and it worked!

Its cheap insurance and you can buy it from Pelican!

Replacing it is a snap.

[david914]

Not uncommon when doing any work on the brake system. Disconnect the battery for a few seconds and it'll go away.

[jmeany]

I hate to tell you my temporary cure....

Remove the bulb.

[Jdub]

No, no...you've got it all wrong: Click and Clack recommend the electical tape over the offending light. That's the ticket!

Have you checked your brake lights yet? That is, how "quickly" they come on when you press the brake pedal? If they come on late, you are due for two new brake switches at the master cylinder. OEM is pricey, but they last: VW equiv. are cheap but you'll be back in there in about 8 months.

Have you done as David recommends? That is the solution. Do not attempt to pry the red cover from the brake light switch -- you will break it.

John

[jmeany]

I took the car to Boston On Friday to spend the weekend with my Daughter. Everything works ok. I will try the ground strap solution and I will look at the switches. The brake fluid was just flushed with new stuff when the brake job was done. The Rear Brake Lights do work. ( I owned a 69 Beetle and when the bulbs burned out the light would come on.) I did not check the timeing of the light VS Pedal action but I will.

[Groesbeck Hurricane]

Did you disconnect the battery as David suggested? This might take care of your issue.

[jmeany]

Nope not yet... Mothers day and all.. Serious ass kissing.. ya know..

Tomarrow is my B-Day. Guess what I'm doing...

[briansc]

Disconnecting the battery will almost certainly make the lamp go out. You must however turn the key to "on" and then remove the battery. This will reset the switches in the MC. Turn the car"Off" and then reconnect the battery. If the light comes back on, then there is a problem and some thing else is wrong.

[Kurt B]

When mine went on, i was at a loss for a very long time as to what it was. Knew pads were fairly new. After a couple of weeks I began to realize it was the master cylinder. Car braked fine--couldn't tell under braking. It was only when stopped at a light holding the pedal that I noticed the pedal would gradually lose pressure. If you just pushed the pedal outright and held it there, it would eventually (after a few minutes) make its way all the way to the floor. Changed the MC, and the problem is rectified.

[jmeany]

The m/c was changed out too. Thatnks for the procedure on the batery. I thought it was as simple as disconnecting the battery. But, it does make sence leaving the key on. Especaily if there is a "volital Memory"

[3.2 CAB]

If none of the mentioned fixes have worked, have you checked the switch at the parking brake? I have had them to get out of adjustment and the light would not go out till the switch was adjusted to the proper position, another thing could be the wire from the same switch could be pinched by the parking brake mounting plate causing the circuit to ground and make the light come on. I had one that was that way, loosened the bolts pulled the wire out from under the edge of the plate, light went out.

[jmeany]

I had checked for the pinched wire but could not figure out how to adjust the switch. Can you fill me with knowledge on that? Also If the E-Brakes were not done ( I read some wher that they use drum brakes for the E-brake along with discs for the service brake, Two seperate systems. Is that true or did I interperate the reading wrong?

[3.2 CAB]

That is correct, they have disc brakes for stopping, and drum brakes only at the rear for a parking brake. If you look on the right side of the parking brake housing near the brake handle pivot bolt you will see a screw and a curved slot. The switch has a little pin that rides in the curved slot, you can use a small screw driver on this pin to raise or lower the switch in the slot. Just loosen the screw enough to be able to make the switch slide in the slot. You loosen the screw so you can slide the switch up or down in that curved slot. You need to have the car IN gear so it won't roll, have parking brake OFF, ignition ON so it makes the light come on. Loosen the set screw enough that you can slide the switch up or down in the curved slot till the light goes off then tighten the set screw. Apply the parking brake, light should come on, release parking brake and make sure the handle is going down all the way, light should go out. If it does not go out try adjusting it again, it takes very little movement to get it to work correctly. Good luck.

[jmeany]

Thanks for the information. Is there a page I can go to get information on adjusting the E-brake/ replacing the linings?

[Brother]

What ended up working, JMeany?

I'm about to tackle the same problem today.

[Gunter]

Get a Bentley repair manual.

[Brother]

got one

I was just doublechecking here to see what usually is the problem.