The inlet to outlet temperature change on a condenser should be 20 degrees F minimum to 50 degrees maximum for a tube and fin condenser. A serpentine or parallel flow condenser may read 60-80 degrees F maximum. This can be checked with the temperature clamps on the Mantooth gauges. Put your low-temperature clamp on the outlet side of the condenser and the high temperature clamp on the inlet side to test.
Many technicians use an infrared thermometer, but these are designed for shiny surfaces and the beam needs to be close to the pipe to pick up the correct temperature. This can also be done on the evaporator inlet and outlet pipes.
