HVAC blower turning on fan won't start?

Question

Hello,

Our HVAC isn't cooling. This inside blower is going, however the outside fan isnt kicking on. I tested the fuses outside, and there is no resistance. I tried to spin the fan blade, it spins easy, however it doesn't start running. Today I also changed out the thermostat to see if the old one could be bad.

So I have heard that since the motor spins smoothly, the motor isn't bad, but the capacitor could be, however I'm not even hearing a hum come out of the compressor. I have also checked all breakers, and none are tripped.

Even though I don't hear a hum, could it still be the capacitor? Or is it most likely something in the furnace electronics?

Thanks for your help

Answer 1

My money is on the capacitor.

Answer 2

first go to the thermostat and make sure that the fan is on then if the fan is on its either the fan motor or the capacitor

Answer 3

Probably the capacitor. But then again modern HVAC systems are just like cars. They have many sensors, circuit boards, safety switches and relays that control anything and everything in the system. So it could be a number of things-but as others have said i would bet on the compressor/capacitor.

Answer 4

If you don't hear anything from the compressor, than it is the capacitor. The cap is what puts power to your compressor.

Answer 5

By saying you don't hear a hum, I have to ask is the contactor making any kind of noise?.  If it is making noise have you reset the circuit breaker for the compressor? Turn if all the way off and then back on.  Sometimes one side of the breaker will trip and not show being trpped.  If the breakers are ok and the contactor is not making noise, and you feel comfortable doing this, do you have access to a multimeter? Pull the disconnect next to the compressor, this will turn off the 240 volts the unit runs with, then look for some smaller wires going to the contactor.  These are the low voltage wires that send 24 volts to the contactor.  Make sure the thermostat is turned on, set it for a temperature lower than the current room temperature. Are you getting voltage to the contactor? If the answer is no check the W wire at the air handler and at the thermostat.  The G wire runs the inside blower only.  This is why you can put the fan in the ON position and not have the compressor running all the time. If you are getting voltage at the contactor turn the power back on at the compressor, take a sturdy insultaded rod, very dry wood or plastic remember electricity can kill damp wood can conduct electricity.  Look for a small bump in the center of the contactor.  Press it with the rod and see if the compressor turns on.  If it turns on when you press this point on the contactor and off when you release it then the low voltage side of the the contractor is bad.  If the bump is pulled in and the unit is not running take the multimeter and carefully check to see if your are getting 240 volts across the two bottom connections and then 240 volts across the top of the connections.  If you are getting 240 volts on one side only the the contactor is bad and you need a new one.  Turn off ALL POWER this is the breakers for both the compressor and the furnace.  Again make sure the power is off.  Make a diagram of the wire positions, then disconnect them.  Remove the contactor and take it to an electrical supplier or an HVAC parts supplier and get a new one.  Reinstall it and reconnect the wires.  Turn the power back on and everything should be working again.  

Good Luck

Answer 6

thermostat or check capacitor

Answer 7

I would check the circuit breaker for the compressor (if this is a split A/C system).  Some times these trip due to the element being weakened due to voltage surges (storms, etc.).   Also, if you feel comfortable doing this, check the power on the line feeding the compressor to see if you have voltage.  I would only do this if you are experienced with electrical circuits---it can be dangerous.   It could be the capacitor for sure.