I just installed a GFCI receptacle in my bathroom and at the same time I'm replacing an old light switch and another receptacle downline from the new GFCI. For some reason the GFCI trips when anything is plugged in the downline receptacle or if the light switch is switched on. Somehow I'm just not wiring it properly, but I'm at a loss. Attached is a photo of the array of wires in the switch/outlet combo. There are 2 neutrals, a red that is tied in with a black and two blacks split from one. Any ideas? Thanks very much.
The GFCI is sensing a shared neutral. You need to wire the GFCI so that the incoming hot and its associated neutral are on the line terminals. It may not be possible to protect the down stream receptacle with this GFCI (wired to the load side), you may need to have two.