I've noticed over the past two weeks that our central air unit is staying on most of the day. We have it set at 75 and have it on AUTO. Now I know when it hits 76 that its suppose to kick on.. and kick off at 74 right? Well the problem is that it will run for about 6 hours during the day and not drop down 1 degree at all. Its blowing out really cold air though. But as it starts to get cooler outside then the tempature starts to drop in the house and the Central Air will turn off. It works fine in the morning turning on and off like its supposed too.. and works fine at night time... but its just during the hottest part of the day when it wants to stay on and not turn off... We had someone come out and he cleaned out the unit outside and told us that was the problem because it was so dirty.. We live in Oklahoma so its really hot and humid during the summer time... but I don't remember it staying on all day long last summer.. I remember it kicking on and off all the time not just at night time or in the morning time... So like we have it set at 75.. It will go all the way up to 77 and stay on for that about 6 hours and then when it starts to get cooler outside it will start to drop and turn off at 74. Frustrated PLEASE HELP!!

It sounds like the AC is struggling against the sun to keep your place cool. If nothing significant has changed (windows left open, trees trimmed to allow the sunlight to hit the house) I can't think of anything mechanical that could be malfunctioning, as it seems to work well in the morning and evening.

That's what my husband told me. He said if there was something wrong with it.. it wouldn't work during the morning or at night time. Our unit on the outside is positioned on the worst side of the house when it's the hottest outside! I just noticed that we are using a lot more electric this summer then we did last summer. Like 3-600 more kilowatts a month. It is hotter and more humid this summer though I guess...

Is it normal for it to run for 6 hours and not even drop 1 degree at all?? It does this during the hottest part of the day... but when its cooler out like in the morning and at night time.. it runs fine. It runs for probably 10-15 minutes and cools off the house and shuts off.. and then comes back on in about 30-45 minutes later when the tempature rose in the house.

Maybe your condenser is dirty and is working harder? Have you had it cleaned this season yet?

As an idea to help the condensor: you might consider planting a hedge around the condenser to shade it from the sun. At least a foot or two away from the unit, but close enough to shade it.

Is your thermostat a LuxPro? Mine is, and it works the same way. The unit turns on at 1 degree higher and shuts off at 1 degree lower.

The reason why is because the unit is not powerful enough to cool the house when it's hot out. What I recommend is that you set it to a bit warmer, like 77, because 74 is hard to get during the day for any house. Mine only goes to 76 in the day when it's hot, because I have a huge sliding glass door that lets in a lot of heat in the living room.

I set it up to 76.. and its doing the same thing. My uncle who is a heat and air guy is coming over today to hopefully figure out what the problem is.. or if there even is one I should say! I am wondering if what I consider cool air.. is really cool? Or if its not cold enough?

We did have our outside unit cleaned about 2 weeks ago. It was pretty dirty.

Chances are there is nothing wrong, it's just that the way the house was built, it lets in too much heat or is not sealed enough. Windows let in ridiculous amounts of heat as well.

It if goes to 76 in the day, consider it working fine.

Ok well my uncle came out and took a look at it. He said the only problem he can see with it is when he put his pressure gages on the outside unit. One of the gages went to 400 and some... he said there looks like there could be a restriction somewhere in the line. He hasn't done this stuff in a while so he said he's going to go home and read his books and stuff to see what it could be... but it blows out cold air.. he said our airflow in the house and stuff is good. He also didn't have his electric meter or whatever with him so he couldn't test that stuff... but just from the pressures he said we have a problem. Our line also didn't have any filters on it? If there is a restriction in the line.. any ideas on how much it would cost to get it fixed??

He said he really don't think it's the compressor because obvioulsy its blowing really cold air...

Something is really wrong if the compressor is blowing out really cold air...

Well I didn't mean really cold air... I just mean that its blowing out cool air like it should be... the air is not warm!!

I also do not think there is any problem with a.c, if you have a ceiling fan put it on low and let run, this will help. Also were you live it is probably about 100 F and when the stat is set at 75 that is too much differential for the a.c.
You should be only 10 to 15 differential to put the stat up, this help with my a.c. staying on. Cause you just want to get rid of the humidity.

Pressure of 400 is way too high for the high side. It would be interesting to know if the suction side is normal. However, besides a possible restriction, the unit could be overcharged if your last service was incorrectly done when the unit was cleaned.

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Originally Posted by Glitter7

Well I didn't mean really cold air... I just mean that its blowing out cool air like it should be... the air is not warm!!!

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Hehe, compressors (outside unit) blow out HOT air and the air handler inside is the one blowing COLD air... hehe...

WE had a very trust worthy company come out. He did a ton of test.. including a pressure test.. electric meter test.. and he also did a valve test on the compressor. The first thing that we found out is that our freon was OVERCHARGED... Someone had put way too much in there so he took some of that out. WE had it charged LAST SUMMER... The valve test passed.. the pressure were still high. He did all kinds of stuff.. he called his son.. checked the inside unit etc etc. He said that the problem is the meter cirucit or the A-coil.. I cannot remember what he said. He said with labor and parts it would be 650 dollars... and my husband said well how do you know it's that for sure? He said well you cannot be for sure because you can't really test it. He said we are so positive that it's that.. that if it isn't that.. we will only charge you for how much it cost us to get the part and not the labor. After he fixed the freon problem. We let the A/C run for a little bit.. and then he checked the tempature of the air coming out of the vents in the house.. and it was coming out at 76. He said he likes to see the air coming out at low 60's... Would anyone agree with this diagnosis?

Air coming out of the vents at 76 = air not turned on (only fan is running) or something is again really wrong.

The things that cause the discharge pressure to be at 400 plus are an overcharge of refrigerant, dirty condenser coil, air in the system bad condenser fan motor . The most likely problem might be a restricted metering device in the evaporator coil, this might cause an inexperianced person to add more refrigerant to system to bring the suction pressures up. If the condenser is really clean then I would check the temperature across the evaporator coil (should be 20 degrees) if it is less then this then it probably is not getting the proper amount of refrigerant through the coil (restricted metering device or low on refrigerant charge ) It is best to know the problem before deciding on the cure. My answer is based on your information, hands on is the best.