Knowing the sequence of operation for this type of starting relay can help you diagnose, confirm, or rule out certain service problems. Potential starting relays consist of a high resistance coil and a set of normally closed contacts. The coil is wired between terminals 2 and 5, with the contacts between terminals 1 and 2. Terminals 4 and 6 are used for capacitors and/or condenser fan connections and have no electrical significance to the starting relay itself, as shown in Figure 1. In fact, terminals 4 and 6 are sometimes referred to as “dummy” terminals and are simply used for wire connections.Figure 2 shows how a potential relay is wired to a capacitor-start/capacitor-run compressor motor. Notice that the relay coil is wired in parallel with the start winding and the start capacitor. The run and start capacitors provide the phase shift for starting torque because their capacitances add up when wired in parallel. In fact, both capacitors are wired in series with the start winding and in parallel with the run winding. The run capacitor limits the current that will pass through the start winding when the motor is running, because they are wired in series. The run capacitor also ...