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Jimachelp · Jun 28, 2012, 05:46 AM

Home AC Blower and Outside Unit do not work. I can make the outside unit come on by pushing in the button on the Relay Switch on the outside unit. Both the Fan and the Compressor come on when the Relay Switch is tripped. There is no control voltage (25 Volts) from the Thermostat to the outside unit. Does the Blower have to run for the outside unit to run? Will the Low Pressure Switch prevent the Blower and the outside unit from running? I replaced the thermostat and checked that the Blower spins freely. I am thinking that the outside unit is fine and the problem is with the Blower. The control voltage from the Thermostat is prevented from going to the outside unit because the Blower is not running. Does this sound reasonable? Could the Low Pressure Switch be tripped, but why would this cause the Blower not to work? I am planning to replace the Capacitor on the Blower?

hvac1000 · Jun 28, 2012, 06:36 AM

Originally Posted by Jimachelp

Home AC Blower and Outside Unit do not work. I can make the outside unit come on by pushing in the button on the Relay Switch on the outside unit. Both the Fan and the Compressor come on when the Relay Switch is tripped. There is no control voltage (25 Volts) from the Thermostat to the outside unit. Does the Blower have to run for the outside unit to run? Will the Low Pressure Switch prevent the Blower and the outside unit from running? I replaced the thermostat and checked that the Blower spins freely. I am thinking that the outside unit is fine and the problem is with the Blower. The control voltage from the Thermostat is prevented from going to the outside unit because the Blower is not running. Does this sound reasonable? Could the Low Pressure Switch be tripped, but why would this cause the Blower not to work? I am planning to replace the Capacitor on the Blower?

The blower inside needs to be activated by a relay that also uses 24 volts to activate it. Check the transformer to see if it is putting out 24 volts. If it is not then replace the transformer. If it is then track down the voltage till it gets to a component of the system that will not allow the voltage to pass through. Then you have found the defective component and it will need to be replaced.

Since the outside unit will not work with out 24 volts to send a signal to turn on the problem you are having might be one in the same. A 24 volt signal problem.

Jimachelp · Jul 17, 2012, 04:48 PM

Thanks for the assistance. There was 120 volts going into the transformer and 0 volts coming out. So, I replaced the transformer and it fixed the problem. However, after a few days it stopped working again. I measured the voltage and 0 volts is coming out of the transformer again. The original part number for the transformer is C6349701 and I replaced it with C6349703. Is this correct? What would cause the transformer to keep blowing out? Did I buy a bad one? We have had bad weather, could a power outage blow it?

hvac1000 · Jul 24, 2012, 05:21 PM

Originally Posted by Jimachelp

Thanks for the assistance. There was 120 volts going into the transformer and 0 volts coming out. So, I replaced the transformer and it fixed the problem. However, after a few days it stopped working again. I measured the voltage and 0 volts is coming out of the transformer again. The original part number for the transformer is C6349701 and I replaced it with C6349703. Is this correct? What would cause the transformer to keep blowing out? Did I buy a bad one? We have had bad weather, could a power outage blow it?

A power spike could blow it as well as a short circuit in the low voltage wiring and devices.