Weird problem with AC condenser unit

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Old 08-12-17, 08:25 AM
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Weird problem with AC condenser unit

Hello guys and gals,

I have two approx 17 years old Lennox system systems and the upstairs unit stopped working last night. Observations:
- Thermostat works and (warm) air comes from the vents
- I went to see outdoor unit, I heard the compressor working but the fan was not
- Rotated fan with a stick, fan started to work
- I let the system to run for a few hours but air from the vents is still warm
- Copper lines from the outdoor unit are not cold or warm

Do you think the compressor is the problem even though I can hear it running? If the compressor is the culprit why the fan had stopped. What else might be wrong?

An AC guy (that I don't trust) replaced a capacitor in this unit couple of years ago and said that the pressure is fluctuating and recommended to buy a new unit. I don't want to call him back.

Any and all help and comments highly appreciated!
 
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Old 08-12-17, 08:47 AM
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Often, if the condenser fan on the outside unit can be started by giving it a push, the fan capacitor is bad. I would suggest that you try replacing the fan capacitor. Most systems use 2 capacitors, one for the compressor and one for the fan. They often use a dual capacitor (2 capacitors in a single can). If you have a dual capacitor, you can either replace it with a dual capacitor (same value in microfarads for both sides), or add a single capacitor for just the fan. The fan uses the smaller of the two values (if dual capacitor).
 
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Old 08-12-17, 08:55 AM
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Thanks Bob; I was hoping the fan capacitor was the issue but as I got the fan rotating by starting it manually , the copper lines were "room temp" and warm air was coming from the vents. Sounds like there is something else wrong in addition to the fan capacitor.

Adding: The unit probably has a dual capacitor, if both sides are bad I still can hear the compressor running which is strange.
 
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Old 08-12-17, 09:28 AM
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Dual caps are two separate caps. Its possible just the fan cap is bad.
 
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Old 08-12-17, 09:39 AM
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Hi, I understand but I got the fan running by rotating it with a stick and still no cold air from vents. If both sides of the capacitor is bad and the fan is running and I hear the compressor too can the issue still be with the capacitors only?
 
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Old 08-12-17, 10:01 AM
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If you hear the compressor running then either it is internally bad or you have no refrigerant left. You're going to need to call for service.
 
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Old 08-12-17, 10:24 AM
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OK thanks. I just called a tech that my wife knows.

Is it possible that bad fan capacitor caused fan not to start resulting in a compressor failure? I'm assuming the fan didn't work for about 5 to 7 hours last night.
 
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Old 08-12-17, 10:51 AM
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The compressor will usually get hot with the fan not running, but most/all compressors have thermal shutdown built in, meaning that if the motor gets too hot, it shuts itself down until it cools off. It's unlikely that the fan not running would have caused a loss of refrigerant. With any luck, you're low on refrigerant and the compressor is still good. If the refrigerant is low/out, be sure to have the tech check for a leak. These are sealed systems, so you should never have to add refrigerant unless you have a leak or a system component replaced. If refrigerant is added to the system, unless the leak is repaired, it's just a matter of time before the refrigerant leaks out again.
 
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Old 08-12-17, 11:31 AM
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Hi Bob, great to know. The tech came in, replaced the dual capacitor and we get cool air again. He hooked the gauges and said the pressures look OK. It's really interesting to know that the compressor was not functioning properly even though I got the fan running manually. Maybe both capacitor sides were bad. Now I know weird things can happen, I'll probably buy a spare capacitor so I have one to try next time. The bad cap was actually just a year or two old, made by Genteq.

Thanks gents again for the comments.
 
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Old 08-12-17, 11:42 AM
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Glad to hear that everything is working well again. Capacitors are relatively inexpensive and simple to replace, so having a spare on hand is a good idea. Thanks for letting us know that you got it working.
 
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Old 08-12-17, 12:11 PM
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Totally my pleasure, Bob!
 
 

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