Thermostat says “Cool On” but compressor is off outside.


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Old 12-30-18, 07:54 PM
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Thermostat says “Cool On” but compressor is off outside.

I live in Florida. The temperature was in the high 70’s today and humid. My house temp was 74 and also humid. I set the thermostat to 73.
The AC clicked on and cold air came out of the supply vents immediately. Everything seemed ok. Then after 3-5 minutes, warm humid air started coming out of the vents. I checked the thermostat. It still displayed a temp of 74. It also said “cool on”, when the cool was most certainly NOT on.
I walked outside to check the compressor. It was off? I stood there for a minute to text a friend. While I stood there, the compressor did something odd. It was turning on for 1 second and immediate shutting itself off. It repeated this cycle over and over.
This wasn’t looking normal, so I ran inside to set the temp on the thermostat to 75. The thermostat clicked, the “Cool On” was no longer being displayed, and the fan ran for about 2 more minutes with the ”cool on” display off, like normal.
I just had an HVAC technician out to check it, and he said it seems to be working properly. No freon leaks, no maintenance needed. It’s only a 1 year old unit.
Why does the thermostat say “Cool On” when my compressor was not on outside?
Why does my compressor turn on and right back off, repeatedly?
 
  #2  
Old 12-30-18, 07:58 PM
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What you described was a pressure safety control keeping the unit from running, and cycling the unit.
Some equipment has these, others do not.
Also could have been another safety switch such as condensate overflow.
It is not good for the unit to cycle like that.
 
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Old 12-30-18, 09:29 PM
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Welcome to the forums.

I just had an HVAC technician out to check it, and he said it seems to be working properly. No freon leaks, no maintenance needed.
I agree with roughneck..... it would appear your system is in need of refrigerant.
 
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Old 12-31-18, 04:51 AM
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Hi, if the tech thought that cycling was normal it’s time to switch Co.
Geo
 
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Old 03-20-19, 06:43 PM
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Problem Solved

After another visit from a service technician, the source of the short cycling was found. Apparently, my 1.5 year old unit had some bad wiring (the fault of the shoddy construction of the building, not from the HVAC installation)... So the original tech who came out to fix the wiring issue “topped off” the freon. That was not necessary. There wasn’t a leak, and it passed all the tests when he was troubleshooting the wiring issue. Why he “topped it off for free” is a mystery.

The second tech that came out said that it had pressure readings that were off the charts. He went through the steps to remove/release some of the freon, and tested/repeated the process until the numbers were within the normal range for my unit.

It’s warming up in Florida, and so far, so good! My AC hasn’t worked this well since I first moved into this apartment. Hooray for knowledgeable technicians!

Thanks to everyone one for the feedback and brainstorming.
 
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Old 03-20-19, 06:51 PM
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Released the refrigerant? Like blew it into the atmosphere?
 
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Old 03-20-19, 06:52 PM
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I can't see how wiring inside the building could cause that unit to short cycle.

Why he “topped it off for free” is a mystery.
It sure is and it may have been low even though he said it wasn't. He may have overcharged the system while adding. We don't know. We can only guess.
 
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Old 03-25-19, 04:18 AM
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Bad Wiring - Not the Cause

The original issue was due to bad wiring. The unit was not short cycling the first time it had an issue. It was just not working at all.

It was the original issue. The service tech repaired the bad wiring. He identified the issue with the wiring only after running all of his prescribed tests and checks.
 
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Old 03-25-19, 09:13 PM
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While I stood there, the compressor did something odd. It was turning on for 1 second and immediate shutting itself off. It repeated this cycle over and over.
Why does my compressor turn on and right back off, repeatedly?
This was the problem you posted in your first post !
 
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Old 04-01-19, 02:30 AM
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Cause of Short Cycling

The problem has been resolved. Thanks to everyone who provided valuable feedback.
 

Last edited by LexMod; 04-01-19 at 03:09 AM. Reason: Reword
  #11  
Old 04-01-19, 05:10 AM
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What was the fix for the problem?
 
 

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