B737-800
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Total 20000
Time Pressure
Aircraft Equipment Problem Critical
Air Traffic Control Provided Assistance; Flight Crew Diverted; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Landed in Emergency Condition
Aircraft
At 37;000 feet the Auto Fail light illuminated on the air conditioning panel along with the master caution light. The pilot monitoring started the QRH procedure for the Auto Fail Light. During the procedure the cabin was uncontrollable; the cabin altitude went above 10;000 feet and the masks dropped in the cabin. Both crew members donned oxygen masks and initiated an emergency descent. We established communications with the flight attendants and determined all in the cabin were on oxygen and no one had problems at this time. We [notified ATC]; diverted to ZZZ; safely landed the airplane and taxied to the gate.During the QRH procedure; we could not extinguish the Auto Fail light and the cabin became uncontrollable. Small inputs to outflow valve would not correct the situation.
[Report narrative contained no additional information.]
B737-800 flight crew reported a complete loss of pressurization at cruise altitude and that standby control did not recover the system.