AC system performance checks.

DRAFT

TB 9-2320-279-13-1

FIELD LEVEL TROUBLESHOOTING INTRODUCTION - Continued

4. AC system performance checks. Troubleshooting procedure for the HEMTT 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.

(e) The AC compressor clutch engages and 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 receiver/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 20F 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 and the refrigerant and AC condenser receiver/dryer must be replaced after locating and

correcting the cause of the contamination.

(b) AC compressor failure will show up as abnormal noise, seizure, leakage, or low suction and

discharge pressures.

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.

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