Brake light switches

[adam928]

Hi guys,

My brake light switches have stopped working- this second pair have lasted about 5 years!
Has anyone changed to the foot operated system, instead of the over complicated hydraulic original system?


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[adam928]

Ok, changed over the switches for new replacement units, and the brake lights work, whichever switch is plugged in. Now though, when everything is connected up, the brake (pr)! Light still will not stop flashing! Any ideas?!

[riber.bentsen]

Check the wattage on the bulbs. It needs to be the same on both sides, since the system works ny measuring differences in resistance. Could also be a corroded bulb socket. (Not enough to break circuit, but enough to draw more amps)

[adam928]

Bulbs both the same, and all metalwork on the sockets and bulbs are spotless!


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[adam928]

No ideas anyone!

[harborman]

Check connections on the board behind the foot rest on drivers side. Pull the connectors and spray with Deoxit. This is the control board for checking bulbs and displaying warnings, worth a try.

[qdac]

You don't say what car that you have. From your comments, I am guessing the early style with the two brake light / brake warning switches on the master cylinder.

Your comments are a little ambiguous - are you speaking of the "Brake Lights Warning Light" or the flashing "Brake System Warning Light"?

I had an issue with my US 1981 928 5-speed where the "!" and the "Brake System Warning" were flashing. I didn't realize that I had this issue until I first replaced the large number of burned out bulbs in my dash display.

What I did was:

• Replaced bulbs in dash, Deoxit all connections. This is when I started seeing the flashing warning.
• Replaced both master cylinder switches. Didn't help.
• Investigated wiring from master cylinder to Central Warning box under dead pedal. Found disconnected wire don't remember which one - re-connected it. Didn't help.
• Purchased replacement Central Warning box off E-bay. Didn't help.
• Reflowed solder connections in Central Warning box. Fixed some problems, but not this one.
• Replaced master cylinder and bled system. This fixed it.

I have tested the system (using the WSM procedure) and it now works correctly in the error and normal modes.

IIRC, you have to disconnect the battery to clear this error. Otherwise no other changes will cause the flashing to stop.

Good Luck!