Standby Pack Average Temperature If all zone controls and primary pack controls fail, the standby pack controls command the packs to produce air temperatures which will satisfy the average temperature demand of the two cabin zones. The trim air modulating valves will close. The flight deck zone Temperature Selector will have no effect on the standby pack controls. Fixed Cabin Temperature If all Temperature Selectors are positioned OFF, the pack controls will cause the left pack to maintain a fixed temperature of 75 degrees F (24 degrees C) and the right pack to maintain 65 degrees F (18 degrees C) as measured at the pack temperature sensor.