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The red light on the dash is an indication of a brake system pressure imbalance, and indicates that the master cylinder internal assembly is not "neutral" between the front and rear ports. The switch on the MC is actually just a "normally open" switch that has a pin that rests between the front and rear MC plungers. When the plunger is pushed unevenly from front to rear or vice versa, the pin is pushed into the switch which closes the circuit.

This can be caused by losing pressure on one end of the brake system versus the other (front to rear), such as when bleeding only one end. Or it can be caused by a failure of one of the set of internal MC seals. Try bleeding the brakes. Sometimes it is necessary to bleed the master cylinder as well as the lines.

And it was only automatics that had an emergency brake indicator switch, which caused the red indicator to light up. But all models have a rocker switch on the lower dash console that, when either end is pushed, both the rocker and dash light should glow.

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