Hello.

I have two Carrier AC units, one for the upstairs and one for the downstairs. Last year, both units worked fine. Now, my upstairs unit is not working. The fan on both the inside and the outside is working, but it is not blowing cold air. My downstairs unit blows fine.

Now, I know very little about HVAC. The unit outside is clean. What are the possible scenarios of why my unit isn't working properly?

I am generally distrusting of all contractors, so I am looking for real information that will lessen the probability of being had by someone. Do you think it needs to be charged? Is it a leaK? (I don't see one, but I don't know where to look.)

What do you all think?


Thanks!

Are these window units or central air?

There are several possibilities, one being that you have a leak and you are low on freon, second it could be a dirty coil which is unlikely if you have changed the filter often, It could be the start capacitor on the compressor and it is not cooling.
Turn the unit on and feel of the copper tubes that are connected to the condensing unit and see if there is a difference in the temp of the two lines. The small 3/8's inch should be warm... the larger line should be cold or at least cool. If there is a slight difference you probably need freon.

Quote:

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Originally Posted by letmetellu

There are several possibilities, one being that you have a leak and you are low on freon, second it could be a dirty coil which is unlikely if you have changed the filter often, It could be the start capacitor on the compressor and it is not cooling.
Turn the unit on and feel of the copper tubes that are connected to the condensing unit and see if there is a difference in the temp of the two lines. The small 3/8's inch should be warm.....the larger line should be cold or at least cool. If there is a slight difference you probably need freon.

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OK, I've checked the copper tubes and the smaller one is a little cooler than the larger one. Plus, I've noticed that when I place my hand over the fan in my condenser unit, it is blowing cool air outside. Now when I place my hand over the unit that works, the air is warmer. Also, the small copper tube on my working unit is warmer and the bigger unit is cold.

Now when I did buy this house it was a deal that they guy who owned it had a wife who recently died and he decided that he couldn't keep it up and pay for all if the bills himself; so I am not ruling out the possibility that the filters weren't changed properly.

I still don't know if these are windows units or central, but letmetellyu has covered all the possible problems. :)

Is it possible that you have heat pumps? If you do it could be possible that the defrost timer on the unit is not working properly.

When the unit is working properly the air coming out the top of the unit should be about 25 degrees warmer than the normal air outside, and the large copper pipe should be very cool and some moisture on the copper itself.

One way to tell if you have a heat pump is to see if your thermostat has a setting for auxiliary heat, that is not a positive proof but a good indication.

One question, is this unit every putting out cold air, like after setting for several hours. if so this could be a sign that your unit is low on freon or that the evap coil is dirty and the evap coil is freezing over and blocking the air from passing through it.

Quote:

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Originally Posted by letmetellu

Is it possible that you have heat pumps? If you do it could be possible that the defrost timer on the unit is not working properly.

When the unit is working properly the air coming out the top of the unit should be about 25 degrees warmer than the normal air outside, and the large copper pipe should be very cool and some moisture on the copper itself.

One way to tell if you have a heat pump is to see if your thermostat has a setting for auxiliary heat, that is not a positive proof but a good indication.

One question, is this unit every putting out cold air, like after setting for several hours.? if so this could be a sign that your unit is low on freon or that the evap coil is dirty and the evap coil is freezing over and blocking the air from passing through it.

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My unit doesn't have an auxiliary heat setting on the thermostat. Also, the air is actually blowing hot air, so I haven't tried to set it for several hours. I might try it tonight after around 2am, so I will know by tomorrow morning.

Now if it is indeed low on freon or the evap coil is dirty and/or blocked, how much should I expect to pay to fix something like this? Also, if they say that it's the heat pump (if I have one), how much will that be approximately? And, is there a way for me to know for sure if I have a heat pump?


By the way, it is a central cooling unit, not a window unit.

Prices vary greatly in different parts of the country. Also different companies have different rates. Therefore it is impossible to give you a very good ieda of what the cost would be.
Some Tech's charge by the hour and others charge for what they do. I am one that charges for what I do. Therefore fifteen minutes of checking out a circuit board might cost the same as unstopping a condensate drain.

I wish I could tell you closer to the charges but it is just not that easy.

Quote:

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Originally Posted by letmetellu

Prices vary greatly in different parts of the country. Also different companies have different rates. Therefore it is impossible to give you a very good ieda of what the cost would be.
Some Tech's charge by the hour and others charge for what they do. I am one that charges for what I do. Therefore fifteen minutes of checking out a circuit board might cost the same as unstopping a condensate drain.

I wish I could tell you closer to the charges but it is just not that easy.

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Ok... now, is there another way to know whether there is a heat pump? Also, is there something I can do before I call a tech to perhaps fix the problem?

What make and model of unit do you have... you'll find this information on the label on the outdoor unit.