Another brake light question

[OneLethal87GN]

I haven't driven my car for a few days. I got in it this morning to go to work and before I got out of my driveway the brake light came on and has stayed on ever since. The brakes don't feel much different than before the light came on. The powermaster isn't more than a few years old. The pedal has always felt a little soft. I just had the brakes bled several months back due to a solenoid going bad in the rear brakes. Even after bleeding them the pedal was still somewhat soft. I need this fixed a.s.a.p. due to it being my daily driver but don't want to throw a bunch of very expensive parts at it to fix it. I've read the pros and cons of a vacuum conversion but would rather fix the powermaster. I know buying used parts is a gamble but so is buying new parts that may or may not be the problem. Do you guys think it would be the accumulator, brake switch, or the pump?

 

[WHEEZER]

My first guess would be the accumulator ball.

 

[OneLethal87GN]

Well, after that drive I got home from work and parked it for a few more days. When I drove it a few days later the light went out after about 4-5 miles. It stayed out until I drove it again later. It has gone off and come back on once or twice. The brakes feel the same whether the light's on or off. I do have one more related question. Ever since I got the car the third brake light hasn't worked. I checked the bulb and it's good. The other brake lights work fine. Thanks for the help so far.