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My Central AC condensing unit will not start up but the air handler is running. I can engage the switching relay and the compressor and condensor fan kick in and run. I think it is either the switching relay or the capacitor. If I'm correct, how do I determine which is the cause of my problem?

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  • billandlarri Jul 05, 2008

    Well, it didn't turn out to be the relay (contractor) but replacing it led me to the real problem. After replacing the relay and still having the identical problem I remembered reading about the 24V supply to the relay that causes the relay to switch. We discovered a trapped cat under our house a few weeks back before we turned on our AC for the summer and thought noting of it. I discovered the cat had tried to escape through the opening where the cold freon line enters under the house. As it clawed through the insulation it broke my 24V line to the relay. Once I reestablished the connection my problem was solved. Thanks!

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It is the relay. THe capacitor doesn't control both the compressor and the fan. (Some use the same capacitor but it is seperated internally and usually one or the other will still start) This part should cost around $20 Buy whatever they have as long as it is rated at least as much as the one you replaced. Bigger is fine. You may have to cut off the terminals and use the screws.

Posted on Jul 04, 2008

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Were is the reset button on the unit?


Hi, here is the theory on the reset button on Air Conditioners. They reset via the breaker panel box in your house. Check that first before anything else. However if your unit is popping breakers, it is because the rating for the breaker is incorrect, or there is something that needs servicing usually in the outside unit called the condenser. That piece contains the compressor. A faulty compressor and pop the breaker. Or If the condenser fan that blows over the coils of the outside unit stops (common failure) The compressor will overheat and shut down. That may not trip the breaker but the house will get hot anyway. Usual action for this is to replace the condenser fan motor and starting capacitor. Make sure the speed rating and directional rotation for the replacement motor is the same as the motor removed.
There are other reasons why the system won't come one fully. If the wall thermostat is digital and does nothing. including turning on the fan. There will be a small fuse located on the circuit board of the air handler (part of Air Conditioner mounted inside the house. It houses the circulation fan). That fuse could be blown. That one shuts down just about everything.
On air handlers mounted up into the attic crawl space there is an overflow pan. This pan is mounted directly below the air handler. This pan can fill with water when the drain pain contained inside the air handler starts to overflow because the drain system to that is clogged.
There is a "float switch" mounted in the overflow pan wired to the system in such as way as to shut down the entire AC system if that pan fills.
The handling is to clear the obstruction in the Drip Pan inside the air handler. Then remove enough water from the overflow pan and the AC will run as though nothing has happened.
If you have more questions, write to me on this site.
One thing more. The capacitor alone in the Outside condenser unit can fail and that will stop the condenser completely if it is of a "split" design and used for both the compressor and fan. When replacing this unit alone, ALWAYS find the same specification part.
I hope this helps,
Have a Happy New Year,
Mark

Jan 02, 2011 | Goodman CLJ30AR32 Air Conditioner

1 Answer

Fan works but condenser does not kick on


You air handler and condensor run off of two seperate circuit breakers. They share the same control voltage source. With the air handler responding to the thermostat setting, we know you have control voltage. You either have a problem with the line voltage at your condensor or something is happening in the control. Check your circuit breakers and/or fuses to your outdoor unit. Also, look for a red button near the area where the refrigeration pipes enter your condensing unit. Push the red button. If it starts to run, your unit went out on High Head Pressure. A dirty air filter this time of year can cause head pressure problems in the heat cycle (assuming this is a heat pump). Also check for cleanliness of the condensor coil and ensure proper operation of the outdoor fan motor.
There are a couple of components inside the condensor that could prevent it from running. One is the contactor. If the contacts are pitted or if a bug crawled in between them, it will prevent the unit from running. Another component is the Dual Run Capacitor. If this fails, it could prevent operation of your outdoor fan and compressor. Don't forget to check all your wires and connections. Always shut off all power prior to reaching into the electrical compartment.
I hope you find this to be very helpful moving forward. :-)
Testing Run Capacitors

Failed Compressor Contactor



Apr 03, 2010 | Ruud Central System Air Conditioner

1 Answer

Why does my fan runs continus. and the condenser won't run out side.


The fan runs continously because your condensor is not kicking on and removing the heat. The thermostat needs to come under the set temp. to kick off the fan. If your compressor doesn't run and the fan on the outside unit does run, your compressor has an issue. If nothing runs outside, then your transformer on the inside unit(air handler) has an issue. This could also be a control relay on the condenser or the air handler.

Jan 15, 2010 | Omega Trane Furnace Draft Inducer Blower...

1 Answer

4 ton rheem 3yrs old thermostat


It is possible that the relay in the thermostat for "cooling" has gone bad. The relay that runs the blower is different than the condenser relay. Check that you have 24v AC coming from the t-stat to the "y" terminal at the air handler. That same "y" wire should go out to the condenser, make sure then that you have 24v out there. If you have 24v at the condenser then see if the contactor is pulling in. If not then you may have a loss of charge switch that is stopping the current to the contactor. See if you have 24v to the coil of the contactor. If the contactor is pulling in and power is going to the compressor then the compressor has failed. If this is the case the condenser fan will be running but the compressor is not. If neither the condenser fan or the compressor is running then you have a problem in the 24v circuit, which could be a bad wire or a safety switch.

As you can see there are a number of possibilities for your problem. You will need to methodically go through everything to eliminate the possiblities till you isolate the problem,

I hope that this will help you to solve your problem and get you cooling again!

Thanks for using Fixya!

Heatman101

Nov 23, 2009 | Air Purifiers

2 Answers

Fan clicking before starting


If its a DC type variable speed , its big bucks! I typically replace with normal cheap AC type if failure out of warranty, far less money and more reliable!

Aug 23, 2009 | Heating & Cooling

1 Answer

Ac fan on, blowing air, but not cold


Check outside unit if unit and compressor are running feel the large line to see if it is cold. If compressor is running and line is not cold possible charge problems. You may have a capacitor problem outside. they go out quite often. You can change this yourself, Open up outside unit and the cap is the silver bullet with terminals out the top. Bad cap can cause compressor to not operate and also the fan. You need to clean the coil inside or at leat check the coil to see if it is clean. You can clean theis with a toilet brush do not go against the coil bit brush with the fins. You may need to call a service tech but try these options first. russ

Aug 15, 2009 | Heating & Cooling

1 Answer

Whirlpool central ac stopped blowing air, cool or fan only. compressor outside running and attic unit on but no air. Solution??


If you are refering to the indoor fan that is not running, but that the outdoor condenser is operating, the next place to check is the circuit board in the air handler, this is the control for the fan motor. the relay may be bad that actuates the fan circuit. if the relay is bad there will be no power to the fan motor. If you have power to the fan motor then the motor is bad and the motor and capacitor should be replaced.

Jul 20, 2009 | Heating & Cooling

1 Answer

Ruud achiever compressor not running


Relay could be problem. See if thermostat makes relay click. If it does and you hear compressor try to run when it closes, everything is good in control circiut. Then check Start and Run capacitors. May be just one capacitor with 3 terminals on it. If there is any oil leaking out of it or if its swelled, Thats the problem, Replace it with same size capacitor. Mark wires before you remove them. If you hear relay try to close but no sound from the compressor, Check the High Pressure switch. They usually have a red reset button. If its tripped, Could be the condensor fan motor or grass and **** blocking air flow on condensor coil. If you hear no compressor noise and high pressure switch is not tripped but relay acts like its working, Replace relay. DANGER!!! High Voltage!!! Make sure that all power is off of both units before touching wires. Hope this helps. Let me know. Am on yahoo IM as kstfas if you yahoo.

Jul 05, 2008 | Ruud Matching Split Air Conditioner

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