H4-00 error code on Sharp AR-5516, AR-5518 , AR-5520 or AR-5316 (press and hold down 0 key to see the second two numbers from the error on the display) means that the main heater lamp abnormally low temperature detection.
You simply reset the error code by entering the simulation mode: #, interupt, C, interupt, then input 14 then press start.
Unit should power off and the restart. If the error code is still on the display, call a service technician.