As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PERFORMED AN AIR TURN BACK TO MSP DUE TO PRESSURIZATION ISSUES. ON CLIMB OUT, BELOW 8000 FEET, FLOW LIGHT ILLUMINATED. COMPLIED WITH QRH. PACKS DID NOT RE-ESTABLISH UNTIL DESCENT. NO EMERGENCY WAS DECLARED. MAINTENANCE TROUBLESHOT AND FOUND WATER IN DELTA PRESSURE SWITCHES AND LINES. REPLACED DIFFERENTIAL PRESSURE SWITCHES PRECAUTIONARY AND COMPLETED PACK CHECK OUTS.