97 monte_clicking noise from master cylinder area

[stymie_gb]

For the past week or so i have heard a clicking type noise coming from directly behind my firewall in the area of the brake master cylinder. i think this is the abs pump. i can be wrong tho. when i apply my brakes the car stops fine but this annoying clicking sound continues. i also noticed that every time it clicks that my lights dim a bit. is my abs pump or control unit gone or going bad or can it be something else. i cant figure it for the life of me.