Hi. My first post here and apologies if I don't have electric language straight--I'm pretty much self taught and limited to replacing switches and receptacles or adding another outlet on an existing circuit.
So I finally got around to a "roundtoit" of adding a GCCI and additional receptacle to a basement circuit that has 4 things plugged into it. I replaced the single receptacle (2 3-prong outlets) with a GFCI and kept the original receptacle so I'd have 4 places to plug things in. This is in an unfinished basement where the conduit is exposed and the receptacle was installed in a 4" square box with a metal cover the outlet was screwed into. I replaced that cover with a metal one that had 2 cutouts, a big rectangular one for the GFCI and a normal one for a receptacle with 2 3-prong female connectors. I had to remove "wings" from GFCI then both receptacles bolt into the metal cover through the normal holes at end.
ALSO, this conduit and the 2 wires extend out to the garage and the three outlets and light fixture in the garage are on the same circuit.
So what I tried to do was (1) wire in the new GFCI and (2) use the load side to protect the 2nd receptacle in the same box AND the stuff downstream in the garage. All seemed fine when I tested by pushing the "test" button on the GFCI. BUT, I recently bought a GFCI tester that has 3 lights to indicate if wired correctly and a test button to trip the GFCI. This does NOT trip the GFCI when plugged in directly, nor when plugged into the second receptacle in the same box nor in the garage. So something is wrong. (sigh, so much for my "simple" Sat night project
I thought I was very careful to wire from the circuit breaker to GFCI, then use the load side of GFCI to wire second receptacle and then run wires to garage from that receptacle. There were only 2 wires running to the original receptacle and then on through conduit to the garage (there is another circuit that went to that box and then out a different conduit, it was not wired into the receptacle I replaced in any way). These 2 wires, black and white, were not cut but rather about an inch was bared and wrapped around the screw on each side of receptacle, then continue out to garage. The receptacle was then wrapped with electrical tape.
When I rewired I cut the continuous wire but I didn't wire to the screws as both GFCI and other receptacle had the option of sticking stripped wire into holes in back of receptacle and that seemed easier since the two receptacles were so close (sorry I don't know the terms for this but the bare wire sticks in and on the GFCI I then tightened the screws to hold wires in, on the other receptacle they are held automatically and you have to push in on a clip with a screwdriver to release them).
The only other thing I did (that I remember

is when I first wired this I _only_ wired to the one square box in basement and left the wires out to the garage disconnected. This let me confirm that I was correct that the garage outlets ran from this wire as the garage was dead when I flipped the circuit back on. At that point I tested the two receptacles with a circuit tester (two wires with little light, LED I think) but did NOT try the self test button or the GFCI tester (or at least I don't remember for sure if I did either).
Sorry to be so long winded but trying to include all details that might help someone figure out what I did wrong. Other than triple checking that I got the line and load side correct I'm at a loss--so I tried Google on internet and ended up here.
BTW, I did check that power was off to GFCI and downstream when the GFCI trips with self test button (my understanding is if I got line/load goofed up the outlets might stay live when test trips GFCI).
So, any suggestions of what I did wrong or what I should do next? I did check the GFCI tester in a couple other GFCI outlets in the house and it tripped the GFCIs just as it is supposed to do. So what did I do wrong that it doesn't trip the GFCI on my new installation?
BTW2, the circuit breaker is 20 amps, the GFCI 15 amps at receptacle with 20 amp downstream protection. Brand is Leviton, part of a 3 pack I bought at Lowes, Menards or Home Depot recently. Everything is in .5" metal conduit with 12 gauge solid wire (I'm in the City of Chicago
TIA for any help/ideas.
jim bash