Why won't the compressor run
This can be for a variety of reasons. It ranges from something as simple as no supply power (blown fuse, open breaker, faulty contactor, or run capacitor) or it could be more serious as a grounded or open winding in the compressor motor. My suggestion to any novice and or person without proper tools and knowledge; First check the low voltage (24 volt control voltage) by turning on the "Fan on" switch located on the thermostat to on, not "Auto" The blower fan should come on, indicating there's 120 volt and 24 volt available. Fan doesn't come on is an indication that there's no control power. The next step would be to check for power at the transformer and fuse located in the air handler. There should be 240 volts feeding the transformer, and 24 volts coming out. The control voltage is needed to operate the thermostat (which is the switch that sends the 24 volt signal to the compressor contactor to turn the compressor on/off. This 24 volt also powers other relays and switches in the system. knowing that 24 volt is available also tells you that the problem is most likely in the condensing unit (outside, where the compressor is located). At the condensing unit you should check for 240 volt supply power. Upon finding 240 volt supply power the question now becomes whether or not the thermostat is calling for anything (cool or heat if the unit is a heat pump). There should be 24-30 volt available at the small gauge wires feeding the contactor coil. While having the thermostat set at a temperature lower than the current room temperature (in the cooling mode) the thermostat should send a 24 volt signal to close the compressor contactor and turn it on. The non-metallic end of a screwdriver can be used to depress the moveable part of the contactor. After pushing in the contactor, should the compressor start then you may only need a new contactor. It may just hum because of a faulty run capacitor or grounded or shorted internal motor windings (grounded or shorted windings are usually indicated by tripped circuit breaker and/or blown fuse). It's a good idea to have a good multi-meter and knowledge of use before attempting any repairs or diagnosis on your own. I recommend some basic knowledge of electricity before even thinking about attempting any repairs or diagnosis.
May 08, 2014 |
Goodman Manufacturing Goodman GSC130421...