Why would cool air be blowing out of my central ac unit condensor that sits outside? The other unit I have next to it blows out warm air and responds well to thermostat changes. The unit blowing cool air still cools the rooms it contros... but much slower than the other unit does.

check and make sure outside unit is running. should have warm air coming out of condensor

either you have refrigerant leak or compressor bad.

The AC unit outdoors must be running and rejecting heat by its air flowing through it the 2 copper lines are the refrigerant lines, the fatter one should be "beer can cold" if not its low on refrigerant or not running.

When was the last time you cleaned the evaportor coil and condensor coil???? When its cool outside the condensor if its plugged with dirty can mantain the right condensor Head Pressure by useing the cool outside air when it has to run with 80 to 100 degree air it can't get the head pressure with in range to cool the freon. I would clean the condensor coil.......

Your central cooling unit is not performing correctly. You will need to take this to a shop and they will fix it for you.

Depending on where you live, you would need another
200.00 to buy the freon and another 60.00 to buy the
refrigerant gauges.

Turn the unit off outside, turn your thermostat all the way to cool and as low as it will go. Go back outside
and turn the power back on, The condensor fan and the compressor should both be on.

If neither one is on, or one is and one is not then 40.00 might be able to buy you a hard start kit

If it does not have a furnace or heating elements for heating, then it is a heat pump, which is rare for a central AC system, but makes sense of the fact that it blows warm air when you reset the pressure switch, which may indicates freon pressure charge problem if your AC system has a reverse valve and uses freon to for heating (heat Pump).

Do you get heating when outside unit runs? if you do, check freon pressure levels and top up to required pressures. The button you depress is a pressure reset switch ... that is if your AC system is a heat pump ... which, as pointed above, it is not common for central ACs.

Check outside unit if unit and compressor are running feel the large line to see if it is cold. If compressor is running and line is not cold possible charge problems. You may have a capacitor problem outside. they go out quite often. You can change this yourself, Open up outside unit and the cap is the silver bullet with terminals out the top. Bad cap can cause compressor to not operate and also the fan. You need to clean the coil inside or at leat check the coil to see if it is clean. You can clean theis with a toilet brush do not go against the coil bit brush with the fins. You may need to call a service tech but try these options first. russ

Cooling comes from what is done outside, if air handler is blowing and you are hearing a sound , may be in the duct work. If you feel warm air in cooling mode then the outside unit is the prob, need more info

Condensing unit is not running check the circuit breaker , thermostat on cooling? is this a window unit if so compressor has problem