Central air conditioning not cooling?

Question

I've got central air. The air temp coming out of the vent was only 7 degrees lower than the actual room temp. A tech put 1 lb of freon in it but that did nothing. I got another tech to come and he cleaned the coil and said that if that didn't work it might need to be "weighed back in" --- there might be air in the freon and it needs to be emptied, vacuum the air out, and then refilled. A year ago, the previous owners did have somebody put freon in so it's very possible that they got somebody who didn't know what they were doing. He was planning on doing this on Monday, if the coil cleaning didn't work. It's MUCH worse now since he cleaned the coil. The air temp has only a 3 degree difference now, and I think the outside unit sounds "different" than what it did before. I might be wrong though and just looking for things. Will I need a new unit? And, should I just shut this off? It's 88 degrees outside and 83 degrees in here. The heat index is 91. The unit has run nonstop for a week.

Answer 1

Ours was doing something similar and it was freezing up inside...turn off the AC part for awhile and run the fan only for several hours.  Make sure your filter is clean. After several hours if this does not help when you reset the AC part....it may be a relay. If the unit is old you may have to replace it. But leave the fan only on at least five hours to thaw it out if it is froze inside. Hope it helps...

Answer 2

You can get a tech to help you troubleshoot it at the link below. There's just not enough info in your post to give you a clear answer, sorry. The guys over there will ask you questions on the forum and you can take your time answering them in a conversation. Good luck.

edit: in the meantime. Turn it off for at least five minutes. Then before you restart it run a sprinkler over the outdoor coil... it can't hurt anything and just might help.

edited link

Answer 3

This really isn't a DIY problem and I doubt you get any help at HVAC-Talk.

It would probably be better for the system if you turned it off since it is only wasting power anyway.

Let the tech do his job. Sounds like he has a good idea as to what it might be.

Answer 4

You are going to need a tech, I just am not sure I would want either of the ones you have already used.

The first one added refrigerant. If the coils are dirty, a quick fix is to add a bit of refrigerant and to a point it will work until the coils get dirtier and then you have a blocked coil.

The next guy came out and cleaned the coils. Now you have clean coils but too much refrigerant.

It is possible that as some have mentioned you could have moisture in the system which will not function properly.

The next tech needs to be aware of what you have had done. He would need to check the pressure, and reclaim any extra refrigerant. If after he does this, the unit is still not cooling, then he will need to evacuate the refrigerant and vacuum the system and then recharge it.

Answer 5

The first thing I want to say is that it likely is not cooling "much worse" after the coil cleaning. If the delta T, the temp. drop, went from 7 to 3 after cleaning the coil that tells me the coils were plugged up and needed cleaning. The dT is lower only because you are moving more air through it, it is cooling the same.

It also tells me it is not cooling worth a d**n.

If he is suspecting "air" in the system and adding refrigerant did nothing, I am guessing he is reading a good high side pressure. That would tell me the compressor is good. But the problem could also be a restriction,  a plugged up filter dryer or expansion valve. Those also allow you to read a good high side pressure but don't allow the refrigerant to move well for cooling.

And the main reason for air to get in the system is a low side leak (suction side) running it out of refrigerant then drawing in air. NOT a previously "bad tech".  Blaming the other "last guy" is a TERRIBLE practice because you don't know what he saw or did AND conditions change. The problem then might be unrelated to now.

That said I CAN say somebody is not a good tech. LOL.  He has not diagnosed your problem yet. He is just starting with the simple and working his way through it. They call that "shotgunning".

A plugged up coil on a working system should have been a block of ice. With it not cooling now, I doubt it was whether it needed cleaning or not.

BOTH the tech that added the freon and the one that cleaned the coil should have KNOWN it didn't work and was barely cooling before they left.

Air contains moisture and if this guy suspecting air is going to the trouble and cost of evacuating the system and recharging it and he is NOT replacing the dryer (removes moisture) then he is not doing the whole job either.

When he comes back, don't let him leave until he checks that air temperature at the vent and verifies it is working. AND the outdoor condenser should be exhausting HOT air. That is a good check on how much heat it is removing. That is the heat removed from the house.

It should be okay to use as long as it is cooling some. It needs to be moving some refrigerant to keep the compressor cool to prevent damage. But cost is another matter, you aren't getting your money's worth for the power used.

  

Good Luck.

Answer 6

Am going to let the HVAC guys give you specifics but AC works by compressing freon, making it colder, then pumping it through insulated pipes over a transfer stack near or on your heating unit.  The fan comes on, circulates the air over the stack, cools it, and moves it around the house.

Basically, if it is running all the time there are several potential problems;

1. The compressor is not compressing the freon.

2. There is not enough freon in the unit to compress (easy for any tech to measure and opine about),

3. You are freezing up someplace, probably a coil, and air is not getting cooled as it moves over the stack.  That is the most remote of the possibilities.

I am not sure about your description of how they will purge the lines, but usually even is there is air in the lines, it won't be much, and adding freon usually takes care of the problem if it is low on freon or coolant.

If i had someone come to look at the unit, I would ask for an opinion on the pump's tonnage to assure it is large enough to handle the size of your home.  Frequently, the usual one ton pump needs to be upsized.