B737-700
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 140; Flight Crew Type 2098.5
Human-Machine Interface
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence; Inflight Event / Encounter Fuel Issue
Flight Crew Executed Go Around / Missed Approach; Flight Crew Diverted; General Maintenance Action
Aircraft
We were arriving ZZZ with weather reported at 700 overcast and 4 miles visibility. The ILS was out of service; so we briefed and flew the RNAV Approach. This aircraft has no speed intervention. I was flying the approach with the autopilot connected; Lnav and Vnav active; flaps 5 and controlling speed with the throttles. We configured with gear down; flaps 15; then flaps 25. The autopilot disengaged; and would not reengage; so we requested vectors straight ahead and received clearance to maintain 2000 feet. We completed the missed approach; and received a climb and vectors for another approach. We set up and briefed the RNAV Y for this second attempt; then received vectors for approach. Again while configuring; the autopilot disengaged and we executed a missed approach. The weather was less than 1000/3; so there was no approach we could fly without the autopilot. Due to this and our fuel state I elected to divert to ZZZ1. Being in the high traffic approach environment I made this decision without contacting dispatch. Our dispatcher saw the two missed approaches and acars destination change. He contacted us by acars to let us know he was working with the ZZZ1 station and we let him know a short reason for the divert. We landed with 4200 pounds of fuel and the station did an excellent job with the short notice divert.
B737 Captain reported an autopilot failure into IMC airport led to a diversion.