I recently replaced an outlet with a GFCI outlet in a bathroom in an older home (1960s), and added a light/bath fan. In the same box as the outlet I replaced was a single pole switch to a light over the sink. I replaced the switch to match the outlet and wall plate. It was functioning fine before, no issues. It previously was NOT feed via the GFCI outlet. I switched it to be feed via it since it controls a light over the sink, and the new light in the bath fan.
The GFCI outlet feeds the feeds the single pole switch controlling two lights (the one over sink, and the one over shower within bath fan), as well as a 10-20-30-60 minute timer switch controlling the bath fan.
For some reason, the GFCI was tripping when the single pole light switch. Through trial and error, I determined it was the existing fixture controlled by the single pole switch causing the issue. If I disconnected it, everything works fine.
I've tried the following and have not had any luck solving the problem:
- Swapped switch
- Swapped existing light fixture for new one (we were going to replace anyway)
I hooked up a digital multimeter to neutral-ground for fixture causing the problem. When switch is OFF, voltage is essentially 0v (says 0.0008v, something like that). When the switch is ON, it is showing 0.11v. Not sure if that is of any significance.
Attached is a schematic I made. Some of the symbols might not be right, so please go easy on me! If anyone could help diagnose I would be greatly appreciative.