Is there an easy way to check my home AC compressor operation? Is is not starting, and the voltage is OK.?

Question

I have a 5 ton Tempstar AC unit on my house, and today, it stopped cycling on. I checked the voltage, and it is fine 240VAC. The motor for the cooling fan spins freely. Is there a simple check of the compressor? The unit is about 5 years old, and should not have failed yet...

Answer 1

if you hear a humming sound,,turn it off and go buy a new capacitor.

Answer 2

STOP!!!!!!!!!!!STOP!!!!!!!!STOP!!!!!!!!!...

Don't listen to these people, they are gonna get you killed.

Have you ever smelled charred flesh???

Call an HVAC contractor ASAP!!!!!

Answer 3

So your fans are still running..check your fuses or circuit breakers on your compressor if they are still good..there will be a high/low pressure switch and de-icing relay, etc inline with the relay that brings in your compressor... check that cct.. (if you are unsure of what your looking at get an electrician to look at it.. or alternatively.. if there is a cct diagram on the cover or in the encloser have a look for the compressors relay and manually override it to test the compressor.. (use an insulated screwdriver and you should be able to press the relay tag down located on the top of the relays.. (but if your not experienced don't touch a thing...

Answer 4

Shut her down and ohm out the compressor.Underneath the cover you will expose the terminals for the compressor.

C-R will be the lowest,C-S will be a little higher,R-S will be the highest and actually a total of the first two measurements.

Only a couple of makes have a high head pressure reset.

It sounds to me like you have a defective contactor or are somehow electrically dropping a line.Remember, the fan will run more often than not when this happens.Carefully check all the wiring.You could have also blown your refrigerant charge.Defective potential relay or start or run capacitor.

Many many reasons as to why a compressor won't run when it appears you have line voltage.You must go through each check one at a time.

EDIT:Jusy read your update and you sound like your on the right track.Just remember to shut down your condenser if the fan is not operating or your compressor could be damaged due to the elevated head pressure.Good luck.Hope by mid day Monday your cooling again.

Answer 5

no not a simple way to check the compressor it will take an ac man to tell ,but it may be your starter capacitor for your compressor,and you can tell sometimes if it is leaking or bulge out at the top,good luck.

Answer 6

First does the condenser motor turn on and blow cold air outside if yes the compressor is not starting check the following, the run capacitor is the top where the wires go rounded not flat if so the cap is blown. many newer units have a dual cap that runs the motor and comp. one side of the cap could be bad. remove all power to the unit and short the cap with a s***w driver. then check with a ohm meter from common to compressor the needle should bounce if it stays at o ohms it is shorted and needs to be replaced

with no power remove the cover for the wires at the compressor and inspect.

Is the compressor hot or cold, if cold the overload inside the comp could be open, remove wires and ohm the terminals c to r and c to s you should have a reading.

If  comp. is smoking hot the capacitor is more than likely the problem

Caps are rated by MFD or uf   like say you have a three tons system the cap would be around a 40 MFD at 440v this is printed on the side of the cap.

Never check with power on and short caps first the can hold a charge and hurt you!

Answer 7

If it has a reset button push it.

Answer 8

By saying the condenser fan is not working as well, I have to ask is the contactor making any kind of noise?. If the contactor is not making noise, 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