The brakes on my 87 failed. I replaced the relay behind the radiator overflow tank, but the pump would not run. Disassembled the pump and found the brushes worn. Replaced the brushes. Bled the pump, but it does not shut down. Thought it might be the accumulator, but was told a bad accumulator will just caused the pump to cycle on an off. Is the pressure switch the most likely culprit??