In sci.electronics.repair amdx wrote:
could have saved my life.

Good catch.

I unplugged the drill and pushed the test button. The GFCI didn't
pop.

The "test" button on the GFCI should work even if there is no ground to
the GFCI. So you may have more than one problem here.

Inside the garage, no ground connection. I opened the circuit breaker
box and checked the ground wire, it is good. So, in my attic between
the CB box and the garage there must be a connection box where the
ground has opened up.

Don't discount the idea that the ground is open at one of the
receptacles. In three houses I've worked on (one from 1965, two from
1969), if two or more NM cables come into a receptacle box, the ground
wires are just twisted around each other for an inch or two, with no
wire nut. Usually the contact between wires is OK but sometimes the
twist is not very strong. One of the ground wires is longer than the
others, and it goes to the green screw on the receptacle. When I swap
a receptacle in a box like this, I usually add a green wire nut with a
hole in the top for the long ground wire (Ideal "Greenie" or equal), to
help make sure the ground stays connected.

Besides, checking the receptacles is probably easier than fooling around
in the attic.

A good tool for quickly checking grounds is a 100 W incandescent lamp
in a socket that has insulated wire leads. Connect the wires live to
neutral to calibrate your eyes, then go from live to ground. If the
brightness drops off a lot, the ground has high resistance. (If there
is a GFCI in the circuit, going from live to ground should also pop the
GFCI.)

Matt Roberds