Gas and Oil Home Heating Furnaces - AC going out?

I have a condo that was built in 1982. The heating and cooling unit have worked fine until now. I replaced the thermostat in February with a programable one.

I just switched over to AC from heating. At least once a day, it stops blowing cold air. I can tell something has changed because it does not sound the same. I have to shut it off and restart it. That usually gets it working again. I don't know the name of the unit, it think it is a forced air system. It is all self contained inside my condo in the ceiling of my hallway. I have tried to see if something is not working, but I am not sure what I am looking for.

Please help. Do I need to have someone come out and look at it? Are there some trouble shooting things I could try. I would like to avoid a high bill from a tech if possible. Any advice would be appreciated.

Thanks.

Have you looked at the air filter on this unit is it clean???? do you know where it is?? Do this first if not clean put new one in Then if it dont work call tech;) ED

I have checked the filters. They look ok, but did make the problem worse when I put them on. I have removed them completely. That worked well, it increased the flow of the air, but did not prevent it from doing it again.

I talked to a tech I work with and he said it could be the compressor. The fan and the heater work fine, it is the AC that keeps going out. The air continues to come out but it is not cold and it does not have much force. As soon as I switch the fan on, instead of having it on auto, the air force comes back. The air gets cold again once I turn the system off completely and then on again. Could it be the switch. I checked all over outside and I don't see another piece anywhere. I can see that there are pipes running in and out of the unit, but can't see where those are going.

Thanks for any additional guidance.

Well it sounds like the indoor fan is running at the heating speed during both the heating and cooling cycles. Most units will use high speed for cooling and either medium high or medium speed for heating. I'll betcha the problem lies in the thermostat replacement. If you still have the old thermostat, try reinstalling it and see if it cures the problem. The reduced airflow is probably causing the cooling coil to freeze up or perhaps to cycle the compressor on a low freon pressure control. If you keep the fan switch in the on postiion and run the cooling, does it work ok? The outdoor section is probably on the roof.

I tried to run the fan with the AC and it still blows. After a bit, it stops blowing cold air again. Once I turn the AC off and let the fan run it goes back to normal, blowing correctly. I do have the old thermostat, but only the piece with the mercury in it because I did not know where to dispose of it after I replaced it.

The new thermostat I have is Honeywell. Is there one that will work better that I can switch it out with?

Thanks for your help, any ideas on what next? I would like to exhaust all of the options I can before I call a tech so that I know there is nothing simple that I could have done myself.

When you say that it stops blowing cold air with the the fan switch placed in the ON position, exactly what do you mean? It blows warm air but about the same quanity or the airflow is reduced to almost nothing after the unit has run for a while?

dirty evap coil, which would explain it cooling at first then probably freezing up.

When it blows, it blows warm air, not cold. It seems to get stuck on because the air is not cooling the area which tells the thermostat to keep running. I have been turning it off during the day when I am gone so it does not run all day.

Thank you for the information. I have somone coming on Sunday to take a look at it, I also need to have it maintenanced for summer anyway.

If the evaporator coil is the problem. will that be expensive to correct? Can they just clean it or would they need to replace it?

Once again, thank you for all of your help.

If it's just dirty but not leaking refrigerant, the indoor coil can usually be cleaned. However, my procedure is to clean it outside and not in the house. Reasons are I use chemicals and also a lot of water for flushing and can't take a chance on making a mess indoors. It's not an inexpensive repair.

I posted here about 4 weeks ago about my AC. It is a central unit for heating and cooling. I live in a condo that is about 20 years old. The outside unit is on the roof (3rd floor - I'm on 1). The air has worked fine until this summer. I changed the thermostat in February and it worked fine for heating but once I switched it to cool something went wrong. I have had the unit serviced, freon added, the coils were cleaned and the inside unit was also cleaned. After he left from servicing today, it started doing the same thing as before about an hour later.

It runs fine, then I can hear a change in the sound of the unit inside and it starts blowing warm air instead. The only way to correct it is to turn it off and then back on again. That only works a few times. He left today at 12:30 and it is now 10:00 and I am back where I started.

Is it possible that it is the new thermostat? This is my third summer and this is the first time I have had any problems. Please help before I spend even more money to come out to find another solution. Thanks for any advice you can provide.:confused:

tvial:

In order to solve your problem you will have to determine the source of the change in sound. It is a good clue to what may be happening but there are too many possible causes to send you directly to the culprit.
The sound could be the indoor fan, outdoor fan, compressor or burner if it's gas. Maybe set up a chair next to the unit and wait for a change in sound to see what it does.

If you have had it serviced recently I would suggest you call back the same tech. Maybe he missed something.

Moderator note: New thread merged with original post. Please post here to make it easier to follow your problem.

I have taken the filters out and listened for the change. Threre are two fans and they both continue to blow. I thought that maybe there was a belt somewhere in there so I took off some pieces but could not find it. The change in the sound is very slight and you can only tell when you are standing right under the unit. It is an electric unit, not gas.

Could it have something to do with the charge in the unit on the roof? (I am not sure what that means but I have seen it on several other postings.) I notice that when I have it off for a week or so and then turn it on it will work a little. Like yesterday, it had been off for about 2 weeks. I was able to run it and when it started blowing hot air, I just had to turn it off. By the end of the night, turning it off did not do anything.

I am very sorry but the symptoms you are describing are extremely vague and not nearly enough to be able to send you in the right direction.
In order to help you we need information that is specific and somewhat technical. People that try to do this kind of work and come here for advice are expected to have some very basic mechanical and electrical skills and would need an electrical tester to check components. As well as be familiar with electrical safety.
My advice to you again is to either call the original service person or if you don't have any confidence in him/her then do some research to find a reliable company.

It starts blowing HOT air like the heat is on or it just quits cooling and the air is more like the temperature of air in the house? These two fans- you mean there are 2 fan wheels attached to a double shaft motor inside the air handler? Frankly, it sounds like the compressor is shutting down. I think you need a second opinion.

bigjon:

Where is the compressor located and how much does it cost to replace? Is this something I would want to try to repair?

The air that blows out is the air from inside.

GregH:

I feel that I have basic electrical knowledge, but not when it comes to air conditioners. I am not doing the work and feel I also have a grasp on electrical safety. I am just trying to get an idea of where I should be directing a service man because I feel as a woman who does not know much about A/C that I am in a position where I could be taken advantage of.

I am trying my best to provide as much information as I can. I am sorry if the information I am providing is not sufficient. Thanks for your help . :(