b. Testing. (1) Disconnect the power source. (2) Remove the front access panel (para 3-6) and the control box front panel (para 3-25). (3) Refer to the applicable wiring diagram (fig. 1-3 or 1-4) and check for continuity be- tween pins A, B, and C. Note. With power on, 208 volts at relay, and phase sequence correct, continuity should exist between pins 2 and 3 of the relay; if not, replace relay. c. Removal.  Refer to figure 3-11 and remove the phase sequence relay. d. Installation.  Install the phase sequence relay, control box front panel, and front access panel by reversing the order of removal. 3-29. Circuit Breaker a. General.  The circuit breaker protects the compressor from continuous overload and short circuits. b. Testing. (1) Remove the front access panel (para 3-6) and control box f rent panel (para 3-6). (2) Refer to figure 3-11 and disconnect the circuit breaker leads (tag leads for facilitating installation). Test the circuit breaker for conti- nuity with a multimeter set on the ohm scale. Refer to applicable wiring diagram (fig. 1-3 or 1-4) for test points. Auxiliary contacts (pins 3 and 5) are also located on the circuit breaker. When the circuit is on, continuity should exist between pins 3 and 5 of the circuit breaker; if not, replace circuit breaker. c. Removal. Refer to figure 3-11 and remove the circuit breaker. Refer to figure 3-12 and dis- connect the circuit breaker linkage as follows: the  snap  ring  (1,  fig.  3-12) (4) and spacer (3) from switch linkage rod (6) and connector Install the circuit breaker, con- trol box front panel, and front access panel by reversing the order of removal. 3-30.  Rectifier a. Testing. (1) Remove the front access panel (para 3-6) and control box front panel (para 3-26). (2) Using a multimeter, test the front and back resistance of the rectifier. A resistance of in- finity in both directions indicates an open rectifier that must be replaced. b. Removal. Refer to figure 3-11 and remove the rectifier. c. Installation. Install the rectifier, control box front panel, and front access panel by reversing the order of removal. 3-31.  Terminal  Blocks a. Removal and Installation. (1) Remove the front access panel (para 3-6) and the control box front panel (para 3-26). (2) Refer to figure 3-11 and remove the ter- minal blocks. (3) Refer to figure 3-11 and install the ter- minal blocks. b. Inspection. Inspect the terminal blocks for loose terminals and for cracks or breaks. Check threaded parts for damage or worn threads. c. Replacement. Replace damaged or defective parts. 3-32. Compressor and Heater Contractors a. General. Both contractors are located within the control box. The compressor contactor starts the compressor and the heater contractor “ener- gizes the heaters. b. Testing. (1) Remove the front access panel (para 3-6) and the control box front panel (para 3-26). (2) With power off, coil of contactor for continutiy “with multimeter set on ohms. Replace contactor if coil is open or shorted. (3) When contactor is energized, continuity should exist across the line and load terminals of the  contactor. c. Removal. Refer to figure 3-11 and remove the  contractors. d. Installation. Install the contractors, control box front panel, and front access panel by revers- ing the order of removal. 3-33.  Outdoor  Thermostat a. General. The outdoor thermostat is mounted to the rear housing (fig. 1-2) of the air condi- tioner. It prevents the compressor from being started when the outside air temperature is below plus 50° F. when low condensing and suction pres- sures will hamper system operation. b. Removal. (1) Remove the condenser fan guard and fan (para 3-21). (2) Tag and disconnect electrical leads con- necting the outdoor thermostat to the unit. (3) Remove the two screws securing the thermostat to the housing. c. Testing. Test the thermostat for continuity with a multimeter set on the ohm scale. Refer to the applicable wiring diagram (fig. 1-3 and 1-4) 3-15