Had a ac tech service central heating unit for the fall. Tech left and I left to do some errands . Now AC unit is not cooling its blowing warm air. I turned the circuit brks off and on inside and outside. I have also checked to see if unit was left on heater. thats not the problem. If I turn theAC on the fan does not turn on outside and there is no sound coming from the unit outside HELP!!! AC was working properly before this.

Try unplugging the unit and waiting a few which many times resets the board.

Hello, first touch both pipes while the ac is running, the pipe with insulation should cold with condensation and the small pipe should be warm. If they are both warm then the unit is very low on refrigerant or completely out of refrigerant due to a leak, if this is the case you will need a hvac tech to come out, repair the leak, and recharge the unit.

There probably isn't a reset button=magic fix. With it in heat pump mode and tstat set above indoor temp, check your outdoor unit to see if it's operating. If not, check all breakers to it. Can you see any ice accumulated on the outdoor unit? If it is running and not producing heat, turn the tstat to emergency/auxiliary heat. and the heat pump turned off to prevent damage. You'll need a service tech.

add freon and test

There is a possibility that the A/C compressor clutch burned up or got disconnected. Try investigating the wiring for the clutch.

It probably has a low refrigerant charge. The air coming out of the outside unit should be warmer than the outdoor temperature when in the cooling mode and if it's a heat pump it should be colder than the outdoor temperature in the the heating mode. Check the big line going to the unit, it should be somewhere around the 40 F range and the small line should be hot.

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

If you have access to your piping system you may use a soap bubbles to test the pipe connection. the leak gas will blow the bubbles if there is leaking. But if your system is out off freon gas, you can not use this method. just try it check the connection first put the bubbles around it.

You maybe iced up. Turn of AC turn fan on and wait about 45 minutes. If fan is blowing air out of vents chances are you were iced up. Two reason for iceing up are AC coil dirty and low on Freon. You need a service tech to check your Charge on system. If you can get to the coil to clean it grreat. Spray it with water let it set and brush clean with a toilet stool bruch. It will not damage the coil. If it is to stopped up you may have to have a service tech chemicaly clean the coil. Fan motors do go out. ou realy need a service tech to check this Rusty

Sounds like you have a freon leak or your compressor has stopped working. You will probably need a service tech. If it is out of freon, don't let them just add more freon, make them find and repair the leak first. Good Luck.