Tip & How-To about Heating & Cooling

Understanding Air Conditioner Electrical problems is not as hard as you can make it.

Air Conditioners are broken down into two electrical systems, though they work together1. Low voltage control unit 24-28 volt control unit like thermostat and other switches and relays( also feeds compressor contactor,reversing valve, and defrost board on heat pumps)on the outdoor condensing unit .When there is no power to the thermostat,it cannot turn on the indoor fan or any other load (indoor or outdoor). In this case, first confirm there is power available (closed breaker,closed disconnect) If you have power the fan on manual switch on the thermostat should be able to turn on the indoor fan.If it doesn't, then your control voltage is most likely lost. check the transformer and 3 amp fuse in the air handler .2.The high voltage components are your compressor and your fans, both indoors and outdoors.High voltage 240 volt loads are controlled by the 24-28 volt control voltage.3. Remember, a thermostat is just a big on/off switch.4.Be careful and always play it safe when working around energized circuits5. Leave it to the pros, especially if you're inexperienced or nervous about electricity

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We purchased a Amcor Amcoraire Mini Split Unit ? 12000BTU However the Power Transformer Input: AC115-120v 60hz Output: 10.5v 550mA isn't working as per the installer and we can't seem to find it anywhere. Any help?


Hi, this is a 1-ton cooling unit per your numbers. If they just installed it and the line side (120 volts) is good but nothing on the secondary low voltage side, they should have replaced the transformer themselves? If it is a split system, it is normally on all splits to be located in the indoor unit control section. I can't tell you exactly, but look where the 120 volts come into the indoor unit and the high voltage wiring should be connected to it then stepped down to lower voltage. It may have a fuse on the circuit board that they blew when installing it. If you are not familar with electrical, I wouldn't attempt to make these repairs. You can look for a small plug in type fuse to see if it blew, it looks like one on your automobile. I would call this installer out and its there job to do this!! These transformers look different, there not all the same, but will have a black and white wire coming in, and several colored wires coming out for low voltage. It will be in the indoor unit. Keep me posted on what you find or if you need more help. How long ago was the unit installed?
Shastalaker7

Jun 15, 2010 | Amcor AF 12000E Portable Air Conditioner

1 Answer

Have a Ruud AC unit the problem I have after installing a new condenser fan motor when I throw the circuit breaker the unit will not turn on but when I push the contacts on the contactor in manualy the fan will come on but the compressor will not.what do I need to do or order to make this unit work ? I did turn it down to 74.Can you help ? THANKS


The contactor engages from low voltage power from the thermostat as does the outside condensing unit. You may have blown the low voltage transformer or have a loose thermostat wire. Check line voltage(220 volts) to the transformer. Check load voltage(24 volts) from the transformer. If no voltage out,replace the transformer. If you have voltage out(24) check the thermostat wires and the thermostat. If you have a digital thermostat there is a 5 minute delay in the thermostat after power is restored before it activates.

Oct 08, 2009 | Ruud Central System Air Conditioner

1 Answer

my heatpump has quit working I have checked voltage to out door unit it is fine. I have checked low voltage to make sure it is calling it is showing 24 volts from blue to yellow. I have check the uf on the capacitor it is good. I am getting correct voltage into contactor. please help


If all the voltages are correct you might have a bad contactor. Check the low vltage wires that controle the contactor and see if you have >24 volts. There also might be a low pressure not letting it come on.

Oct 07, 2009 | Ruud UBHC Air Conditioner

1 Answer

Goodman SSX16 split system not working


Defective thermostat wire.
Defective contactor.
With the t-stat set for cool and turned down on a low temperature, check for 24 volts at the contactor low voltage hookup. If you have 24 volts, replace the contactor.
You can manually close the contactor to make sure the high voltage is going through it.

Apr 28, 2009 | Goodman CKL60AR60 Air Conditioner

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