MacBook Pro A1502 2015-2016 Works with power supply but not original Apple charger repair

Problem description
Will work off a power supply, but not original Apple charger (stuck at 2.5 V DC in or less) or will boot from battery, but won't charge the battery. The MagSafe light does not come on when plugged in with battery connected and will not switch on. Will switch on with battery only or MagSafe only, but not both connected at the same time.

Symptoms

 * Only charging and working from an external power supply not the Apple one.

Solution
Assuming you've checked U7100 and surrounding resistors, this can often be caused by a bad Q7180. Replace it.