AC Compressor- He gone!


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Old 07-24-14, 12:52 PM
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AC Compressor- He gone!

Well, not entirely. And let me apologize in advance if I get some of the terminology backwards or wrong.

A bit of history:

I replaced the contactor about four years ago on the advice of a forum thread. WIN!
I replaced the capacitor on the blower unit two years ago when I realized I kick start the fan. WIN!
I replaced the capacitor on the condenser unit last year when I realized I could kick start my fan! WIN!

And I have read many epic threads here including allenzachary's air condition conundrum of 0-12. Great read by the way.

So now, in a nut shell, my stat will call for cool air and my condenser *MAY* not come on. If I cut power to the unit, turn off my stat, and give it a second, then flip power back to the condenser and then turn on the stat and ask for cool air - I get cool air as the condenser starts right up.

Thus far, I updated my stat thinking maybe that was the problem and I wanted a programmable one anyway. FAIL!

So, my question is what problem would cause the AC to stop working randomly with the fix being a reset in power (basically flipping the breaker to the condenser) and a new request for cold air?

Could the contactor be out again?
Low pressure?

I am no bueno at HVAC so your help is really appreciated here.

Thanks in advance!
 
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Old 07-24-14, 01:19 PM
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Where are you turning the power off, inside or outside?
 
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Old 07-24-14, 03:27 PM
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These intermittents are always hard to diagnose, especially via the internet. However, if I wanted to try something, I would try replacing the compressor capacitor. It appears that you replaced the fan capacitor last year, but didn't replace the compressor cap. Once the unit has been running, pressure builds up inside and it takes more "oomph" to get the compressor started. If the compressor start cap is starting to go bad, that could cause the symptoms you're experiencing.
 
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Old 07-25-14, 06:42 AM
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Thanks for the replies....

I am turning off power at the breaker box to reset.

And it has been tough for a novice like me to track down. I will check the second capacitor today.

I am wondering if coolant pressure is low. Last night it would come on with no issue but it could not cool the house until the outside temp was around 80 degrees. I think I will call an AC guy today. My wife and kids were troopers last night, but it was pretty humid an 86 degrees in the house when the babies had to go to bed. I don't want to drag this out over the weekend.
 
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Old 07-25-14, 09:51 AM
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That is a Permanent Split Capacitor (PSC) compressor which requires a RUN capacitor, if the mfd rating is low it could affect its ability to start & run properly.

Unless one was added it would have no start capacitor.
 
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Old 08-04-14, 06:31 AM
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To update this thread:

I have had two AC guys out. First guy said it was a dirty evap coil. Granted, it was a little dirty, but not that bad. I cleaned it and there was no difference in my problem. He also said the freon level was not low.

The second guy came out but during his service call, we had unusually low temps and rain. So it made his diagnosis pretty difficult. He checked the freon level, fan motor, etc... same as last guy and decided that the freon was a little low. He added .6lbs. And he said he would return when we got back to our normal 100+ degrees for this time of the year. I suspect that will be this week.

In the meantime, I have still struggled with the system intermittently cooling. Through trial and error, I have determined that the compressor shuts off. The fan is still blowing, but the comp itself is not running.

When I get home today, I am going to recheck the capacitor and post up.

What else besides overheating would cause the compressor to just stop working during a cooling a cycle?
 
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Old 08-04-14, 07:55 AM
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Could be going off on a high pressure control; should show-up on the gages though.

Did anyone check the compressor & fan motor amp draw independent of the other?

Did anyone, with the power off, check the compressor terminals to see if they were burnt, etc?

Did anyone check the voltage of each individual leg of power at various places?
 
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Old 08-05-14, 08:39 AM
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Thanks for the reply. Neither of the AC guys have checked any voltages or terminals (at the compressor) I am sorry HVAC RETIRED but I have not checked the voltage either. I went out there yesterday to try and do that. I took the access panel off and was just looking at everything taking mental photographs etc when the compressor just kicked on all of a sudden. It had been off for a long time before that. The house had heated up to 85 degrees with a ambient temp of 93 degrees outside. I screwed the panel back on and went about taking care of my kids.

Honestly, I am afraid of electricity after getting zapped as a kid. I want to check it but when it comes to AC I never feel comfortable. I have this multimeter: Sears.com

I will check it but I never know exactly what poles to check and where to put the leads exactly. I must seem like an idiot to you guys.
 
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Old 08-05-14, 09:37 AM
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Do NOT try to check the voltage; too dangerous for you!
 
 

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