FIELD LEVEL TROUBLESHOOTING INTRODUCTION - Continued
4. AC system performance checks. Troubleshooting procedure for the PLS AC system includes system
performance checks. A properly functioning AC system will have the following characteristics:
(a) The fan control switch is set to the desired AC heater/evaporator blower speed position (low,
medium, or high).
(b) The temperature control switch is set to the desired temperature position.
(d) The AC condenser fan motor cycles with AC evaporator temperature.
(f) The AC compressor suction line is cool.
(g) The AC compressor discharge line is hot.
(h) The AC condenser core is hot/warm.
(i) The AC hose between the AC condenser core and AC condenser receiver/dryer is warm.
(j) The AC condenser dryer is at outside temperature.
(k) The inlet to the AC expansion valve is warm.
(l) The AC evaporator core is cold.
(m) The AC discharge air temperature is approximately 20°F cooler than the ambient air temperature.
(n) Condensation water may drain from the AC evaporator core.
5. AC system fault symptoms. The following is a brief description of some of the symptoms or
conditions that may exist if a component fails in the refrigerant circuit of the AC system:
(a) If moisture, air, or other contaminates enter the refrigerant circuit, the AC system will not cool
properly. The refrigerant and AC condenser dryer must be replaced after locating and correcting the
(b) AC compressor failure will show up as abnormal noise, seizure, leakage, or low suction and
(c) A faulty or improperly installed temperature control switch temperature probe may cause quick or
delayed AC compressor cycling.
(d) A blockage in the AC condenser core will cause high system high-side pressure. Frost may form at
the location of the blockage.