If you point the remote control at the Hitachi AC unit and push a button with no response, you might not be close enough to the unit.
Some units require a minimum remote sensor distance of 20 feet. Walk closer to the unit and try the command again.
If there is any furniture in front of the unit or in front of the unit interface, move the furniture out of the way. The sensor of the remote control, which is in the tip of the remote control, must have a clear path to the sensor on the unit's interface.
Examine the sensors on both the remote control and the AC. If the sensors have dirt or grime on them, the dirt might prevent the remote control's signal from being received. Clean the sensors with a moist cloth.
If the remote control is close enough to and pointed at the unit but it still fails to operate, the batteries inside the remote control might be too weak to serve the appliance.
Turn the remote control over and slide the back cover off. Remove the batteries from the remote control and either test them with a battery tester or insert new batteries.Always use the correct kind and size of batteries.
If new batteries fail to make the remote control function, they might be installed incorrectly. Inside of the battery chamber on the back of the remote control are printed or embossed "+" and "-" symbols and possibly an outline of the battery.
If the batteries are inserted correctly but the Hitachi AC still doesn't accept commands from the remote control, there might be dirt or blockage preventing the remote control from working correctly. Remove the batteries from inside the chamber and inspect the metal contacts of the battery chamber. If you see dirt on the contacts, clean them with a cotton swab dipped in isopropyl alcohol. Remove dirt buildup from the batteries as well.
A malfunctioning LED light on the tip of the remote control might be the cause of a remote control malfunction. The LED light sends command signals to the sensor on the interface of the Hitachi AC unit.If the remote control falls to the ground , the LED might detach from other internal components inside the remote. You can use an infrared sensor card to determine if the remote control sends out a signal properly from the LED. If the card fails to respond to the remote control commands, then the LED is broken and you should replace the remote control or have it fixed.