First of all, test the iPad Air. Connect the iPad Air to the power supply, when the iPad screen is on, it can be charged normally, and the charging current can be measured by KM001 USB voltage tester.
Use screwdrivers to remove the screws next the iPad lighting port, and then use CPB screen heating pad to heat the iPad screen, after heating for a while, we can use LCD sucker to open the iPad display screen, and then remove it.
After the iPad battery replacement, the problem is still there, which means it's not the problem of the iPad battery, so we suspect that there is problem with the iPad motherboard.
Disassemble the iPad Air again, remove the iPad display screen, disconnect the iPad battery, and then remove the iPad motherboard.
Observing the iPad motherboard, no obvious damaged traces was found. Use digital multimeter to measure the iPad battery connector, it’s found that the BATTERY_NTC and BATT_SWI_CONN signal of the iPad battery connector J7500 is short-circuited.
Use Fluke digital multimeter to measure the iPad battery connector second pin BATT_NTC and the first pin BATT_SWI_CONN, the data measured of them is 0, which is short-circuited.
Attach iPad motherboard to the PCB holder fixture, and then put it under the microscope to fix the short-circuit problem.
After the short-circuit problem was solved, connect the iPad motherboard to the iPad display assembly, turn it on, connect the iPad to the computer via Apple lighting cable for charging, now the iPad can be charged when the iPad screen is off, the iPad charge failure has been fixed.
Assemble the iPad Air, turn it on, and then it gets into the IOS system, test the other functions, all works well.
Hope your iPad is all right. If you have other questions about iPad, please share with us in the comments.