Hi @mohammed8989
If you have a DMM (digital multimeter) check if there is 20V DC on the red and black wires on the plug of the DC-In jack in the laptop (supplier example only to show part), when the charger is connected
What can sometimes happen is the centre pin in the jack breaks internally and this opens the +ve leg of the power connection between the charger and the motherboard.
If this happens then the motherboard receives no power to operate i.e. no charging LED and the battery won't be charged either.
Here's the hardware maintenance manual for the laptop. Go to the bottom of p.78 to view the procedure to remove/replace the DC-In cable assembly. You really only have to gain access so that you can unplug the cable from the board and then check if any voltage is present on the wires when the charger is plugged in.
If the jack is faulty it cannot be repaired, it has to be replaced. Search online for Thinkpad T450 DC-In jack to find suppliers that suit you best.
If the jack is OK then there's a problem on the motherboard and further testing using the schematic diagrams for the board would be needed to find the problem.
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