Place the air conditioning thermostat's function switch in the "Off" position, which prevents the inside unit from sending a 24-volt signal to the Ruud condensing unit.
Disconnect the electricity to the Ruud condensing unit at the disconnect switch. Follow the high-voltage wires from the unit to the metal box mounted on the side of the house. Open the box and either pull out the bus bar or flip the switch to the "Off" position.
Remove the screws holding the Ruud condensing unit's service panel with a 1/4-inch hex-head screwdriver. The service panel covers the side of the unit where the refrigerant lines enter the unit.
Slip a flat-head screwdriver into the seam between the bottom of the service panel and the condenser's lip. Twist the screwdriver and lift the panel off of the Ruud condenser.
Wrap a piece of masking tape around each contactor wire. Write on each piece of masking tape which Ruud contactor terminal the wire connects to. Because a Ruud contactor does not have clear terminal identification marks, use terminal position descriptions like "Top right," "Top left," "Bottom right," "Bottom Left," and so on.
Disconnect each wire from the Ruud contactor. Pull the wires with terminal connectors off of the contactor's blade terminals with pliers. Grip the connector not the wire. Loosen the four terminal screws holding the wires without terminal connectors with a Phillips screwdriver, then pull these wires free of the contactor.
Remove the two screws holding the contactor in the Ruud condensing unit with a 5/16-inch hex-head screwdriver. Pull the contactor from the unit.
Set the new contactor in the Ruud condenser and secure it with the two mounting screws.
Secure each wire to its respective contactor terminal using the masking tape tags as a guide. Press the wires with terminal connectors onto the contactor's blade terminals with the pliers. Tighten the terminal screws with the Philips screwdriver.
Replace the Ruud condenser's service panel and secure it to the unit with the panel screws.