The AC compressor turns on if contactor pushed manually.

The problem is any of this, faulty thermostat, faulty contactor or shorted loose wring.

Check if there is 24 volts coming to the outdoor unit through the Y or yellow wire connection at the outdoor unit. That is the wire that gets 24 volts to turn on the outdoor unit for heating and for cooling.

The blower is the indoor fan, is this turning off in 15 seconds?
If it does your problem is probably inside. Do you have a float switch on the drainline?





If you are getting 24 volts to the outdoor unit when cooling demand is applied, check the time delay if you have one and check across the pressure switch(es).

------------

If there is voltage through the Y (yellow) wire and it does have 24 Volts. Then the contactor may be bad,.

---------

Sometimes wires get broken at contactor.

see below for example:--

call the cooling from the stat check for 24vs on the pair of low voltage wires going into the compressor...should have it there...see if you have a low or hi pressure switch might be open..find the hot R wire to get the contactor to pull in from the stat...trace the contactor 24v wire back from its slip clip..some thing is open.