A/C blowing cold but very little comes out?


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Old 07-16-11, 08:04 PM
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A/C blowing cold but very little comes out?

The ac in my house comes out cold, but very little comes out through the vents. We were cleaning the coil this morning and noticed that if you turn the fan on by itself and with the panel off the unit in the attic, it blows really good, but as soon as you put the panel back on the unit very little starts coming out again..I have a new pleated filter installed, the compressor is good on freon, and the coil is clean, the only problem is that very little comes out, almost as if it were starving for air.....any suggestions would help, thanx...
 
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Old 07-16-11, 08:18 PM
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Let me see if I understand what you have written. When you remove the panel to change the filter and run the blower you have a strong airflow from the discharge registers BUT once you replace the filter and the access panel the airflow drops to a minimum. Is that correct?

If I have restated it properly then the next step is to try it without installing the filter and see if there is a slight improvement in airflow or a major improvement. If it is a major improvement then the filter you are using may be of too high a micron (or MERV) rating for your system. If it is only a slight improvement then you have one or two possible problems.

The first thing to look for would be what are called "filter grilles" at the return air grilles. These are often installed when the air handler (blower) is installed in an attic so that the filter(s) may be changed from the living quarters instead of the attic. If you have filters in your grilles then they are most likely almost totally plugged with dirt. As long as you don't mind going into the attic to replace filters you may remove the filters from the grilles. If you choose to retain the filter grilles (install new filters, obviously) then do NOT use an additional filter in the air handler itself.

The other possible problem is a crushed return air duct or (worst case scenario) a woefully too small return air duct.
 
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Old 07-17-11, 08:11 PM
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Thanx for the suggestions, I tried removing the filter and seeing if I would get more airflow but it's still the same. It's just weird because if you run the blower in the attic by itself with the cover removed I get a very strong air flow, but as soon as I put the cover back on the AHU it cuts the air flow down by more than half. The only other thing I can think of is maybe I have a restriction somewhere that as soon as I put the cover back on it cuts the air flow down, or a bad blower....
 
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Old 07-17-11, 10:14 PM
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Did you check for filters behind the return air grilles? Do you hear a whistling at the return air grilles when the blower is running? If you DO hear the whistle try removing the grille completely and see if your airflow improves. You can also do at least a partial internal inspection of the return air ductwork with a flashlight and mirror from the return air grilles once they are removed.

Do you have this same problem when in heating mode? If yes then it points to a poorly designed return air duct system. Unfortunately this is not uncommon in residential practice and can be expensive to fix.
 
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Old 07-18-11, 08:25 AM
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I would want to know if it is just for cooling or does it happen with heat cycle as well? I would also not recommend using anything but the cheapest filters you can buy and change them monthly , There are certain filters that are to dense or thick that restricts air flow doing more harm then any good . Try that . What happens if you run it with no filter and door is put back on ?
 
 

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