<p>I have seen several postings in forums about the power connector on some ender 3's being bad and causing issues or just burning out, potentially causing a fire.</p>

<p>How can I tell if I have the bad power connector?</p>

If you can measure the voltage at the main board where the bed power line is attached, or at the last point in the wiring prior to the connector, then measure the voltage at the bed, you can compare the difference to determine if there is loss related to a failing connector.
One certain indication of a failing connector is to separate the components of the connector and see corrosion, discoloration or any sign of burning. The Robo3d R1+ used 10 ampere connectors and the bed draws 14 amperes, according to the research I've done. When I discovered that information and separated the connector, it was an easy answer, as one side was scorched and the pins on the other were corroded and discolored.
Another method, not for everyone, is to use an IR camera and examine the leads carrying the power to the bed. The failing portion will be absorbing some of the power and heating itself, which will show up as a bright portion in the power path.