20. Low side and high side? What is the difference? Without getting too technical, the high side is red/large and low side is blue/smaller. The blue side is will be the #10 hose going back to the evaporator case and firewall fitting. The red/high side heads toward the condenser and connects to the top of the condenser with a #8 hose. A receiver drier is mounted/connected to the bottom left of the condenser with a supplied hard line. From the drier #6 hose is used to connect to the firewall fitting then to the expansion valve on the evap case.