Reoccurring Brake Light Problem
 

I am the owner of a black 1982 928 with a 5 speed at around 95,000 miles. After noticing my brake lights were out the first problem found was that the connector to the rear brake light switch located on the master cylinder had somehow worked its way loose. After plugging the switch back in my brake lights worked fine for a day or two. My stop lamp light on my dash lit up again and no brake lights. I then proceeded to replace the rear brake light switch itself which looked a bit dirty to fix my brake light problem once again for about a week without a problem. Today on a hot day, my central warning light started flashing along with brake pressure warning on my instrument cluster. My brakes seem to be fine, the owners manual states a flashing brake pressure light means one of the circuits in the brake system has failed. My brake lights do not work unless i am pushing the brake pedal hard close to the floor. electrical aspects of the car such as turn signals, reverse lights, tail lights, window wipers, headlights all work great. i have tested fuses. i will start with one question:

How do i diagnose a problem such as this and where do i start?

Sounds like rjm65 and you had the same problem. He replaced his switches and the problem went away. Bad switches my man.

usually if you replace one of the switch on the master you do them both

Yeah, from what I heard, they are hard to get to, so replacing both is good advice.

Did you bleed well? Could be air in the system.

bleeding
 

when replacing brake switches, is bleeding the brakes required?