Our mini split AUX (2 tons.) stopped working, and displays a message on the screen that says only E3, what does it mean and how can I fix it so it works?

As far as my split units go, ( Kelon ) the E3 error code
Means: fault of the indoor coil temp. sensor.

The E3 revealed after I cleaned the indoor radiator and fan with an air blower I don't know what to do?!

The E3 Error on the AUX ASW A12H4 / HSAR aircondicioners, also known as Becken in Portugal and Fujita in other countries is caused by a fault in the copper sensor that connects to the indoor evaporator (radiator) on the right side of the unit.
This sensor is a NTC 5K sensor, meaning that when it's 25c it has a resistance of 5K Ohm
To replace this sensor simply disconect your unit from the plug in order to safely open it without getting an electric shock, take the front cover off, take the two air filters off, locate 3 screws hidden on the lower front part of the unit inside the swinging vents (you will have to manualy open the vents at an angle in order to locate the screws, gold colored in my case) take off the 3 screws, and then on the top part of the machine you should see some plastic clips, simply unclip those and remove that half shell, on the right side you should see a wire leading to a sensor inside the copper tube in the radiator (evaporator) simply slide it off , you will have to cut some tie cables, and then on the far right you should see the pcb main board, you have a plastic clip hodling it down to stop it from sliding off , get it off and then disconect the sensor from it, save the plug for later, buy another sensor on eBay and then solder the plug into the new sensor, put everything back together and voilà, your aircondicioner is back online