Chapter 10, Problem 9SQ

Refer to the circuit shown in Figure 10–6. Assume that when the thermostat contact closes the compressor does not start, but the condenser fan and evaporator fan do start. When troubleshooting the circuit, a voltmeter connected across the compressor contactor coil CC indicates 0 volts. A voltmeter connected across the high-pressure switch indicates 0 volts, and a voltmeter placed across the thermostat contact indicates 0 volts. When the voltmeter is connected across the low-pressure switch it indicates 24 volts. Which of the following conditions could cause this problem?

a. The refrigerant pressure is too high.

b. The compressor contactor coil is open.

c. The refrigerant pressure is too low.

d. The thermostat contact is open.

Fig. 10–6 Pressure switches are often used in air-conditioning circuits.