Circulating refrigerant vapor enters the compressor, where its pressure and temperature are increased. The hot, compressed refrigerant vapor is now at a temperature and pressure at which it can be condensed and is routed through a condenser. Here it is cooled by air flowing across the condenser coils and condensed into a liquid. Thus, the circulating refrigerant removes heat from the system and the heat is carried away by the air. The removal of this heat can be greatly augmented by pouring water over the condenser coils, making it much cooler when it hits the expansion valve.
2Be sure the furnace’s circuit breaker is on or that its fuse has not blown. Check both the main electrical panel and any secondary subpanels that supply power to the unit. If the circuit has blown or tripped, reset the circuit breaker by flipping it all the way off and then on again. Or replace the fuse. If the circuit blows again, there is probably a short in the electrical system providing power to the furnace. For this, you may need to call an electrical contractor.
Replacing a capacitor is easy. Just take a photo of the wires before disconnecting anything (you may need a reference later on). Then discharge the stored energy in the old capacitor (Photo 4). Use needle-nose pliers to pluck one wire at a time from the old capacitor and snap it onto the corresponding tab of the new capacitor. The female crimp connectors should snap tightly onto the capacitor tabs. Wiggle each connector to see if it’s tight. If it’s not, remove the connector and bend the rounded edges of it so it makes a tighter fit on the tab. When you’ve swapped all the wires, secure the new capacitor (Photo 5).
Furnaces and thermostats are not mix-and-match appliances. Using the wrong type of thermostat with a furnace will cause operating problems and can be dangerous. Although thermostats look similar, they are designed very differently. There are numerous types of heating systems and thermostat systems and they need to be coordinated for safe and proper operation. There are three types of thermostat systems used today: millivoltage, low voltage, and line voltage.​