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I have a ac york unit.. i have 24 volts from inside but the contactor from the unit wont pull... somebody please tell me what to do??

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Can you ohm out the coil on the contactor? If you don't know how to do that get back with me okay

Posted on May 08, 2010


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Outdoor lennox elite ac unit not turning on

Remove the service cover on unit.check and see it the contactor is pulled in if it is then check the disconnect that is the gray box that you see on the wall to see if you are getting 220 volts to it and through it to the unit. if indoor unit is running and outdoor contactor is not pulled in check the 24 volt side of contactor. You will need a metter for this if you are not confident with working with electricity call a service company. electricity KILLS

May 09, 2014 | Heating & Cooling


How it works: Central AC Contactor

Magnetic relays commonly known as definite purpose contactors are used in a variety of different applications throughout the HVAC and Appliance world. They can have anywhere from 1 pole or up to 4 poles or more. The coils on them can be 24 volt 120 volt 240 volt or even 440volt and better.02c6373.jpg Their main job is to power compressors and fan motors on various equipment. On a home unit the contactor is almost always a 24 volt, 2 pole, 30 amp one. Some smaller units have what is known as a pole and a half. or 1.5 poles. The coil pulls down only one side of the contactor, while the common leg has a straight bar across it. On home units smaller thermostat wires connect to the 24 volt coil powered by a transformer.When the temp rises the thermostat calls for the contactor to yank down and power up the compressor and fan outside. If those small wires are chewed up by an animal or a weed eater then power to the coil cannot do its job. Very often the 24 volt coil on the base of the contactor just dies. A couple videos I found on line will give an idea of various types used in home units. A guy had a unit which would not shut down because of fried welded together contacts. He did an autopsy of the old part. I thought it was cool.

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on Aug 21, 2010 | Heating & Cooling

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Outside AC unit not coming on but indoor fan is working, replaced the start/run 5/50 capacitor but still didnt fix it, let it set allday while came home tried it and it came on and worked great, but the...

Sounds like you are on the right track. The symptom of the contactor not pulling is your clue to the solution. When you turn the thermostat down lower than the room temperature and the thermostat calls for cooling, the outside unit should start immediately. There are a few exceptions to this but generally this is correct. So if you turn the system to cool and the thermostat is calling for cool then the contactor should pull in immediately. If it does not then check for 24 volts to the contactor. If you have 24 volts to the contactor then the contactor is the problem. If you do not have 24 volt power to the contactor coil then you will have to find where the break in voltage to the contactor is happening.
There are many reasons why you may not be getting 24 volts to the contactor, so check what i stated above before you go any further. Repost if this is the solution or you need further assistance.
Important tip....the yellow wire from the thermostat carries the 24 volt power from the thermostat to the contactor.

Sep 08, 2011 | Intertherm P3RA-036K Air Conditioner

2 Answers

A/C unit won't come on. I have 230 and 24 volts to unit but contractor won't engage. What could problem be?

Check the 24 volt coil on the contactor for continuity between the 2 wires. I suspect the coil is open. If you have 42 volts ac at the base of the contactor and it ain't pulled in then it is shot. I wrote a tip on this and posted a couple of videos here How it works: Central AC Contactor

Aug 21, 2010 | Goodman CLQ36AR49 Air Conditioner

1 Answer

How do you tell with a voltmeter if the contactor coil is bad?

Check for 24 volts AC at the coil. If you do not have 24 volts at the coil (with AC turned on at your thermostat), then your problem is not with your contactor, but rather a control problem. If you have 24 volts at the coil, check for 240 volts on the LINE side (commonly marked L1 & L2) of your contactor. If you do not have 240 volts, check for open fuse or tripped or bad circuit breaker. If you have 240 volts, check for 240 volts at the LOAD side of your contactor (Commonly marked T1 & T2). With 24 volts on your coil and 240 volts on the LINE side, you should have 240 volts on the LOAD side. If not, the contactor is not making contact.

You can also perform a continuity test as shown in this video:

May 23, 2010 | Ruud UAKA030 Air Conditioner

1 Answer

Carrier central unit outdoor unit will not activate .i have replaced the voltage transformer inside , and the positive contact in the outdoor unit . my local ac man told me that i may have a problem with...

Hi, I would say to check for high voltage at the outdoor unit. You will have 24 volts from transformer on the secondary side of it, and high voltage on the primary side of the unit. @4volts are for all of the controls on the unit, contactor coil, all of the safetys, pressure switches high and low Ect. On a call for cooling, the stat sends power to the contactor coils, 24 volts to energize it and close the contacts and in turn starts the fan and compressor. Make sure you have high voltage at the unit. If not, check the main breaker, or the box mounted at the unit. Most will have 2 fuses in them that are behind a plastic cover. You can ohm them or just replace if your not sure. If you have power. If this is a split system central unit, check at the contactor for high voltage. If you have it, and it will not come on, you have to see if you are getting 24 volts to the contactor coil to pull in. If it does not, the problem is in the indoor unit unless this is a all in one outdoor unit. Please let me no, give me the details please.

Apr 16, 2010 | Heating & Cooling

1 Answer

Contactor not engaging to start condenser unit . When setting the thermnostat, i hear the click from the unit starting inside the house. Fans start and air starts blowing inside the house, but the...

I would replace the contactor if you are getting 24 volts to the contactor and it isn't engaging therefore the magneto on the contactor is out and the contactor will need replacement. If you don't have 24 volts at the contactor then the transformer that sends the 24 volts is bad and will need replacing


Mar 11, 2010 | Heating & Cooling

2 Answers

Compressor fan and compressor not running new 2 yr old system puron

No power to outside unit. Check to see if contactor on outside unit is pulled in. Most AC units inside have float switch. When the drain stops up it shuts off outside unit. Located in overflow or underneath unit. No Problem Rusty

Jun 05, 2009 | Carrier 38CKC036 Air Conditioner

1 Answer

My ac unit does not have power to the thermostat. There is 200 volts going into the transformer and 24 volts going out. There is 24 volts on the back side of a terminal with thermostat wire running to the...

Please exercise due caution in checking voltages in live circuits!

24 volts sourced by the transformer, through the thermostat, then through the contactor (turns on power to compressor/fan) and returns to the transformer, If the thermostat is closed (calling for cool) you will see no voltage across it, but instead the contactor should be energized. Please note, 200 volts seems odd, you should have between 215 and 235. It sounds more like the contactor relay coil may be open. Is the contactor/transformer one piece?

May 15, 2009 | Heating & Cooling

1 Answer

A/C unit air handler comes on inside but outside compressor does not come on. The contacts are not working. If I hold down the contacts the compressor comes on and unit works.

Check and find out if you have 24 volts across the terminals for the coil of the contactor. If you have 24 volts across the terminals and the contactor does not pull in change the contactor with one of the same ratting. If you do not have 24 volts across the terminals for the contactor coil your problem in in the 24 volt circuit. Possible that the thermostat is not sending power to the contactor through the "Y" terminal.

Jul 20, 2008 | Ruud Heating & Cooling

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