Replaced Brake System -- Warning Light Still Stuck On

[jsedlock]

Hi All,

I have read I believe all posts related to this subject, so I'll do a quick summary --

My brake warning light is stuck on after replacing the calipers, brake hoses (SS), and master cylinder. (Master cylinder from Pelican with two new sensors.)

I have repeatedly done the "key on, + battery terminal off, key off, + battery terminal on" and the light stays off for about 3 - 4 minutes. Then the little bugger is back on.

It's not the E-brake switch. I can turn that on/off by deploying the ebrake and the light switches on/off.

I have seen a thread from John Walker re: a small circuit board that sometimes goes bad.

Where is this board located? What else could trigger the brake light back on after the key on/off cycle? I saw an oil pressure sensor could also trigger this behavior?

What other parts do I through at this thing before I go bonkers? :-)

Thank to you all, I love this forum!

[wolds]

You don't indicate what year your car is, but my 83SC has two brake switches on the master cylinder. These pressure switches are prone to going bad (as mine did). The symptom will be as you described as I had the same symptom. If the two switches don't agree with each other as to their state (open or closed) it will light the warning light. They are easy to replace. Warren

[jsedlock]

So sorry, in my confusion over my problem, i forgot to post my car!

Unmodified 1979 911SC Targa.

Both sensors on the new master cylinder are new.

[timmy2]

Do both brake lights work when you step on the pedal?
I had one that was loose in the socket and my light would stay on until I repaired it.
Only way to clear it was to ensure brake lights worked and then remove the negative cable on the battery for a minute.
My car is a '78. So should be the same.

[jsedlock]

I believe the problem is solved. With the battery connected, i pulled both pressure sensor connectors off the master cylinder. Reconnected. Then, did the key on/off battery disconnected/connected and that did the trick. I didn't think these cars had sophisticated electronics (at least for 1979) but there is obviously some logic circuitry buried in there. Thank you for the help!

P.S. The bulbs are slightly loose in the socket, so that was a really good tip -- to check the easy stuff first and be sure the bulbs are making contact.

[wwest]

Originally Posted by jsedlock

I believe the problem is solved. With the battery connected, i pulled both pressure sensor connectors off the master cylinder. Reconnected. Then, did the key on/off battery disconnected/connected and that did the trick. I didn't think these cars had sophisticated electronics (at least for 1979) but there is obviously some logic circuitry buried in there. Thank you for the help!

P.S. The bulbs are slightly loose in the socket, so that was a really good tip -- to check the easy stuff first and be sure the bulbs are making contact.

Battery being overcharged will result in that symptom..

Watch for a bouncing tach for conformation.