A/C unit running, fan blowing, but little air coming out of the vents

I have this problem from time to time where the a/c unit runs fine, the fan in the furnace is running but sounds louder than normal and i can feel a lot of air coming through small gaps just above the furnace in the duct work (where the vent starts right at the top of the furnace). little air comes out of any of the vents in the house.
I have changed the filter.

Any thoughts on what this could be or where to start troubleshooting would be greatly appreciated.
thanks
Mauro

 

Ice. I recommend having the evaporator coil inspected.

 

thanks Houston204. so if i leave it off for a while (a day) then its fine when i turn it on due to ice melting would that be consistent with ice on the evaporator coil?
mauro

 

Yes. A horizontal application is usually not hard to check...


Vertical applications are much harder...

 

thanks! ill let you know what it looks like.
Mauro

 

Houston204, so i haven't taken it apart, but i did turn it off for about 4 hours while i went out and it now works fine. So i think you are right about the ice. I'll take it apart and have a look at the evaporator coils.

So now onto root cause....

the a/c never turns off for some reason so we manually turn it off when the house is cool. we did not shut it off last night, and had this problem this morning.
What are the possible causes for the a/c not turning off ? i have a programable thermostat that i think may be causing it. here is a picture of the thermostat wires. which 2 control a/c? i assume i can manually short them to turn the a/c on and off.
thanks again,
Mauro

 

Lack of airflow and lack of refrigerant would cause the system to freeze up.
These problems would also reduce cooling ability and cause long run times without the ability to properly cool the home.




Vertical A coils are very tough to clean a probably better left to a pro.

 

The house does get quite cold and we do shut it off so its works effectively for the most part. The temperature goes far below the setpoint but the A/C continues to run. This is why we shut it off manually. its a royal pain, and i suspect that is the cause of this icing up, but could be a separate problem. we had a good rain yesterday too so quite humid here and might increase chances of icing.