Central air suddenly stopped working? advice needed


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Old 08-12-10, 11:07 AM
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Central air suddenly stopped working? advice needed

Hello,

I have a Trane 1100 series unit that suddenly stopped cooling this morning. The unit comes on and the fan is blowing but no cool air is coming out. I really know very little about AC units but from a little reading I checked several suspect things.

The Indoor return filters are brand new. The two (freon?) lines coming off the unit do not have any frost on them. They feel only moderately cool. The Air coming up from the blower fan on the outside unit is not hot - feels about the same temp as the air that's coming out from the inside vents. I also tried turning the unit completely off for 40min and fired it back up - same results: fan runs but no cooling going on.

I've called a service tech who won't be out till tomorrow. Ordinarily it would be no big deal but we're having a record breaking heat wave where I live and it's getting near 90 inside the house - approaching unbearable.

I posted here in case there was any other thing I could check for in the event it turns out to be something relatively simple.

Thanks in advance
 
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Old 08-12-10, 12:45 PM
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Check to see if the compressor is running first. It is located in the outside unit either under or next to the outside blower fan.
 
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Old 08-12-10, 02:10 PM
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I don't see a compressor. Only the fan unit and the electrical box. Unless it's way underneath the house.

How exactly do I know it's working?

Any possibility the thermostat switch is bad? It's an old White Rodgers 1F56-301.




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Old 08-12-10, 03:22 PM
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You have to have a compressor. It is in the outside fan unit, we call that unit condenser which has the blower fan and the compressor in there. the compressor is right under the fan. It is a big cylinder-ball type unit. When they start running, you not only hear the fan, you should hear the compressor running too, sounds just like a motor, may be a little louder than fan. The symptom you described indicates the compressor is not running anymore.
 
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Old 08-12-10, 03:43 PM
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You refer to a fan unit that is working. Is it outdoors or inside?

Have you checked the circuit breaker for the outside condenser unit? It will be a 2-pole, 240-V breaker.
 
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Old 08-12-10, 04:05 PM
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Ok. I see the compressor just below the fan. It's hard to be 100% with the fan running but it sounds like only the fan is running. I cannot detect another(louder) sound coming from the compressor.

There's a switch(breaker?) box located just below the power company box right beside the outside unit. Can't tell if its tripped. Not familiar with it. Doesn't look like a standard breaker switch. Black t-bar knob with "on" visibly marked on the far right. If it were tripped would the fan still work?

All the normal breakers in the garage are ok.
 
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Old 08-12-10, 07:22 PM
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Since your fan is running, so the switch box is OK. If you never pay attention to compressor's sound before, it will be hard for you to tell if it is running. At this point, not much you can do, when the AC tech comes tomorrow, he should be able to tell you. Post back here and let us know what the AC tech say..
 
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Old 08-13-10, 04:08 PM
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Turned out to be a bad start capacitor. Reading about half of rated value. HVAC guy said it was an unusual cap. It was a dual type - 30uF + 15uF. He had to call and ask what the other section was for. Apparently the condensor needed near the full 45uF to run properly. He first tried a standard 30uF only and it wouldn't kick on. My unit was an AC only unit and he thought the extra section might be being used for Heating applications for different units.

At least the condenser wasn't gone. Looks like I'm going to have to double up on the coil cleaning. I should have known. I've had to change the indoor return filter about every 3 weeks during this long spell of ultra hot weather we're having. Normally do it about every 2 1/2 to 3 months .
 
 

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