pedal goes to floor brake light on?

I am an 18 wheeler mechanic so my knowledge of hydraulic brakes is slim. Just changed front and rear brakes. When i changed the front left brake fluid overflowed from the reservoir when i compressed the caliper but only on that wheel. After replacing all the brakes i went to test drive but brake light was on and pedal goes to the floor. I tried engine off and pump the brakes hard then start engine but still did not help much at all. When i unplugged the sensor in the proportioning valve the light goes off. I read somewhere i need to reset the valve but unsure how. Main question, should i try and reset the valve or is my problem else where? Also i did not bleed the brakes.