First normally just the LO fan is on with the AC mainly for air flow through the condenser and not for engine cooling. If not on at all (RCM) then when stopped pressures are liable to go sky high and pop the blowoff.
Second otherwise your problem sounds like a blocked high pressure line, as part of your repair process did you blow the lines, condenser and evaporator out ? Particularly after "new compressor blew its seal". For either I doubt that a scan tool is going to help you.

ps there is nothing unusual about the AC itself, find a better shop. Are you anywhere near ACKITS ? 7904 E Chaparral Rd #A110-608
Scottsdale, AZ 85250 602-233-0090