So,
Q1: Connecting the cable to the ''TEC'' port on B side gives better performance only? This action is *not* the solution to your original problem of firmware update/installation?
Q2: How did you finally get the firmware installed/updated? It just decides to behave properly, for no apparent reason?
Q3: How about the 4-pin power cable of the pump? How do you get it connected to the 3-pin connector on the MTEC Control device?