Central A/C blows cold, then blows room temp air after couple hour - daily

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  #1  
Old 07-07-12, 07:39 PM
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Central A/C blows cold, then blows room temp air after couple hour - daily

Going through some hot weather that the A/C unit can't keep the house cool with, so the A/C is running from about 10am through the evening. But suddenly in spell of consistently hot days, it goes through for 3-4 hours blowing cold air, then suddenly it blows warm (or more like room temp) air out and obviously isn't cooling. The outside A/C unit is still running (along with the furnace blower) but there is no cold air. I'm guessing maybe it is low on Freon, but just wanted to run it by the group to see if someone with practical experience knows the common cause. The unit is actually pretty new in that I only converted the house to Central Air about 7 years ago.
 
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  #2  
Old 07-07-12, 08:21 PM
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If both inside and outside fans are running, but all of sudden you don't get cool air anymore, it indicates the compressor stops working. Can you tell if the compressor is running or not ? The compressor is in the outside unit, a cylider unit under or next to the fan. Or you can hand touch the large insulated pipe to see if it is cold or warm ....It should be ice cold.
 
  #3  
Old 07-07-12, 09:01 PM
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Can't see the compressor (I think it is incorporated into its own housing just to the side of the fan with the way the setup is on this newer A/C unit). But I suspect it isn't working as I turned it off for a few hours, then just turned it back on 15 minutes before this typing and it is still warm air and the insulated pipe is warm.
 
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Old 07-07-12, 09:45 PM
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If the compresser stops working, the first thing to check is the capacitor which is a coke can type unit in the outside condenser unit. If capacitor is OK, then you need to check the compresser itself. Capacitor is a DIY item, very easy to replace and it is cheap. But if the compresser is bad, you need to call a pro to fix or replace it.
 
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Old 07-10-12, 05:52 PM
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Just out of curiosity, I was at work where a co-worker chanced to walk by (who is in charge of fixing all of the A/C units for our 50 business buildings across our area out here). He told me a 7 year-old Central A/C unit (and I didn't mention it, but I did spend a bunch of extra money to get some fancy high-end Concord unit that had a large Federal rebate), but anyway, he told me a unit like that would almost never have a Freon leak this early in its life, and also a capacitor would almost never go out this earlier in its life.

He said 9 times out of 10 a seven year old high-end unit like that would be due to the two fuses on the disconnect on the outside wall that you pull out. I have to just check it on a continuity meter. I'm going to give that a try when I can get some out off of work. Any thoughts on if that makes sense? Would fuses also be a common cause? He did just have a stroke a couple months ago, so I'm not 100% sure how well the wheels were turning on his trouble-shooting.

Thanks again.
 
  #6  
Old 07-10-12, 05:57 PM
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IF the fuses popped then it would not run ever. Open fuse = NO POWER.
 
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Old 07-10-12, 06:10 PM
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Funny. I asked him and he said the outside fan run separate than the compressor and you can have a bad fuse and the fan is still running. I'm wondering if he was thinking about the furnace blower as the fan on the actual outdoor unit was running just fine, but the compressor is NOT producing cold air which led me to thinking it had power coming to the unit in general but didn't have a working compressor. I still wonder if it's not the compressor.

As a side question. I know this is bad, but I'll admit it and just ask anyway, I haven't done any maintenance on it and it had a lot of little grass/hay type of build-up on the back side. I'm assuming that is the air intake portion of the unit. Does it impact the compressor at all to not keep the grass and debris off of the intake parts on the outside fan unit?
 
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Old 07-10-12, 06:11 PM
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yes, the compressor must work harder if the coil is blocked.
 
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Old 07-10-12, 06:25 PM
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Thanks. I'll keep that in mind. One last quick question since you're so quick. I was told this unit was on the "low end" of being able to cool a 2,000 SqFt house and was rated between 1,800-2,000 and my house is 2,020. He said the next size up would cool like a 2,500 SqFt house. At the time the couple thousand dollar made sense, but my upstairs ducts have so far to travel they never get much cold air blowing out of the blower by the time they get all the way there. I've since bought an attic fan for my upstairs attic and it helps, but it's always 5-10 degrees warmer in my room than the downstairs living room close to the furnace ducts.

My question is, if I do have to replace something as major as a compressor, can you get a "better version" or upgrade so I'm getting something that can cool my whole house? I'm always regretting now just getting something that can actually heat my upstairs rooms like it does my downstairs rooms since there is so much variance, and I'm sure it is due to the lack of cooling power coming out of that unit. Thanks again.
 
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Old 07-10-12, 06:30 PM
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no, the compressor must be replaced with the correct one for the current unit. Unlikely that a bigger unit would make both floors the same temp. Honestly, unless you have 2 systems it is unlikely that the both floors will ever be the same temp.
 
  #11  
Old 07-10-12, 06:51 PM
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OK. Thanks.

If any good comes out of my research, I just realized my Concord must have a 10 year warranty as every model Concord I can find on their website has a 10 year warranty. So I suppose it is likely that whatever broke down should be under warranty. Now I just need to see if I can find any original info and then I'll just call out a factory tech to replace under warranty.

Thanks again for the help.
 
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Old 07-10-12, 06:57 PM
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sooo. FYI that is probably a part warranty only.... no labor
 
  #13  
Old 07-12-12, 06:15 PM
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Thanks. It was capacitor. Problem solved.
 
  #14  
Old 08-23-12, 02:27 PM
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Ironically, problem wasn't solved.

Just thought I'd follow-up on this thread since it sounded like all was solved and I lived happily ever after.

Weather got hot again once we got home from vacation, went to turn A/C on and it was blowing cold yet again.

Called the Heating & Cooling company who replaced the capacitor and they now told me that the system didn't have enough juice to "kick on" the condenser. He said the fan is blowing in reverse and he thinks the installer put it in backwards (not sure how that could have happened) and that it is only 50% as efficient as it should have been all these nine years since I bought it and it has likely had to work hard its whole life and it has worn it out.

Anyway, he says for $1,000 he can add a "hard start kit" (whatever that is) to give it the extra boost to kick on the condenser ($220). He said he also needs to replace the condenser fan motor ($550). And lastly he needs to replace the fan blade so it will go the correct direction ($220). This sounds a little fishy to me. Not sure why a fan blade is $220 and why it running backwards makes it need to be replaced. And what a hard start kit is.

He also said my 10-year warranty on this unit was only good towards the "condenser itself" and that it is fine, it is the motor and the fan that is the issue, which only had a 5-year warranty. He's trying to talk me into getting a completely new unit.

Any advice?
 
  #15  
Old 08-23-12, 02:56 PM
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Not saying it's the problem but seen fan cap. turn a fan backwards,it's kinda funny.Also slap a hard start on that puppy,might help.Sound high what he asking but not there.
 
  #16  
Old 08-24-12, 07:18 AM
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What is a hard start? Is it a $50 unit that can just be purchased online and hooked up by a DIY from the outside? Or do you pay $220 for someone to have a specific unit built that has to get wired and built into the system?
 
  #17  
Old 08-24-12, 04:24 PM
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A fan that runs backwards is often caused by a failed run capacitor. I think the replacement capacitor failed already.
 
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