2001 Trane central air conditioning unit problems

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I bought my first home in 11/2010 and got a home warranty. This unit is my 2nd floor a/c. When it started to get really hot this weekend, the a/c isn't kicking on when temps get over the set 78 degrees. It's happened four days in a row. I put in a work order through the home warranty company. They sent out an a/c guy and he said the freon was low, he recharged it yesterday. He said he put three pounds of freon in and when he tested the thermostat, he said it was working. That's the problem, It seems the a/c unit works fine when it's not hot and only kicks on late at night/early mornings. when it gets hot during the day, mid 90's, the a/c unit doesn't kick on at all until late at night. I don't get it. I really don't know anything about central air units. what should I be checking? the fan outside isn't running at all and no air is coming from the vents.
 
3 pounds of freon is a lot.

It should at least kick on during the day. If it were low on freon it would freeze the lines and compressor. Otherwise, the thermostat/wiring could be suspect.

You've got issues.
 
I don't kow much about it either but I did read a little about this online. I didn't find much info but what I did find said that when the AC only works when it is cool at night it could mean there is a small refrigerant leak in the system somewhere. Maybe your home warranty company can have a tech check your system for leaks. I read that the average size central AC holds 4 to 6 pounds of refrigerant so if the first tech put in 3 pounds, I would think that might indicate a leak in the system. Hopefully the warranty administrator can get a tech to check the system more thoroughly and get it fixed.

If the AC is outside, maybe one of its capacitors is bad or is getting hot during the day and not allowing the fan or the compressor to kick on. I went through some problems with the AC in my own house in the last two years. Two years ago my outside AC unit stopped working and it was because the capacitor that controls the compressor was bad. They call it a run cap. I bought a new run cap for it, about $50.00 at a very good local appliance parts/service/sales store here where I live. They checked the original run cap to be sure it was bad and I replaced the run cap, all was well until last year. Then the AC quit again, it turned out the other cap, known as a fan cap went bad. This is the cap that controls the compressor fan on the outside AC unit. I bought a new fan cap for about $35.00, replaced it and it was OK until this year. Last weekend the AC quit again. The fan motor had gone bad, the fan wasn't turning and the fan motor was so hot I could not touch it. I replaced the fan motor and bought a single cap that operates both the fan and compressor. This new cap is also better matched voltage-wise to the new fan motor.

I know none of that matters much with the problem you are having but maybe you could check your capacitor(s) or have them checked to see if they are getting hot and not allowing the system to turn on. I read online that the compressor should have a limit switch or safety switch that will turn it off if the refrigerant falls below a certain safe level.

I am no expert at all on this but it sounds like a leak or a heat-related power problem to me. I don't see how you could have bad caps or freon leaks on a two year old AC system but I guess anything is possible. I would say get the warranty folks to check the system again.
 
Saying it's low on refrigerant and the thermostat is working seems kind of lame. I would insist that a more competent ac guy check the system more thoroughly. If it's low, why is it low?

Like the other guys say if it's low it should be checked for leaks. I just finished a class on AC but they don't cover the home units, and the instructor was not great either. So I'm going to be learning the bulk of things on my own.

Couple of things that came up with a quick search.

http://www.air-conditioning-and-refriger...nditioning.html

http://www.ehow.com/how_6009233_troubleshoot-central-air-conditioning-system.html
 
well, the guy left about two hours ago. He went in the attic. he said my condensate pvc drain pipe was clogged. he asked me for a bucket and a cup, he scooped up alot of water from the drain pan. he said he blew the clogged line out and cleared it. I'm a little suspicious. he said he had to come back tomorrow because he said the pvc lines need to be straightened? he told me I would have to pay that out of pocket because the warranty company only pays for mechanical parts. I called the home warranty company after he left, they said yeah, the home warranty company only pays for mechanical parts to get it running again. if the tech got the a/c unit back running again, they don't pay for anything else. the guy said the work on the pvc pipes would only be 65 bucks. sounds unusually cheap though.
 
PVC drain lines like that is very little in materials. I imagine he will do the work in less than an hour. It is possible the slope of the drain lines helped caused the clogging. The condensate can also can contribute to the blockage also.
 
3#'s of refrigerant IS a lot. Either it was under-charged (too cold out?) or you have a leak somewhere, that has gone undetected.

Too many unknowns to troubleshoot effectively from a distance.
 
You should pour a cup of bleach in your a/c condensate drain once a month.

I do mine the first of the month in the morning once I adjust my thermostat to the daytime temp setting. That way the a/c isn't running and the bleach has time to sit there and eat up the mildew, etc.

You should also consider using a good media air filter like a perfect pleat, or maybe practical pleat. I use a 20x30x5 and change it every 6 months.
 
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I'm not really sure if the guy was being honest about 3 pounds of freon low. Reason why I say that, when he came the second time to check the a/c, he said he "blew out" the clogged condensate line to clear it from blockage. but all he had with him was a couple of screw drivers. He said he was coming back Saturday to tie up the pvc lines b/c they were not draining properly, the guy never called at all. so I don't know if he's coming back. it's under home warranty, he probably thinks it isn't worth his time.
 
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