I recently repaired and upgraded two old 2-prong electrical receptacles
to 3-prong. Both receptacles had 2 wires and grounded boxes.

One of the receptacles is now powered and grounded properly. The other
receptacle is powered correctly but has a weak ground -- when I used a
voltage tester, the power light was bright but the ground light
flickered.

I think that the ground fault is either between the metal cable and the
box or between the screws of the receptacle and the box. The metal bars
of the box where the receptacle screws in are very rusted and corroded.


Has anyone had similar problems with this type of weak ground in a
old-style grounded box?
Do you think trying to de-rust the box will help?


Thank you.