Jim Thompson wrote:

Went outside to add another electrical circuit at the BBQ and
discovered that all of my nice wire-tagging had faded to non-readable.

So I couldn't figure out which common went with which hot.

Then it dawned on me to simply trip the GFCIs which releases *both*
hots and commons so a simple ohm-meter check would do the trick.

NOT! Both GFCIs wouldn't trip when I pressed the test buttons :-(

Went to Radio Shack and bought a Receptacle/GFCI tester for $5.99.

At the same time I noticed a gadget to locate breakers... bought it
also ($29.95).

Went home and tested the GFCIs... both have failed :-( Tester was
verified on some indoor GFCIs... it would trip them.

Both bad units are outdoors, so maybe it was the heat (they both face
the western sun... it gets over 120°F here :-). Any other ideas about
why they fail?

The breaker locator is neat... plug a sender unit into an outlet, then
scan the breakers... works like a champ.

...Jim Thompson

The environment, and lack of testing, kills GFCI receptacles
installed outdoors. GFCI receptacles should be tested once
a month, per manufacturer's instructions. They have two
general categories of failu electronic and mechanical.
Mechanical: the electronics operates a solenoid, which
operates the mechanical mechanism to open the contacts.
Heat/cold, humidity, dirt all can combine to gum up the
mechanical works - and that is particularly true outdoors
where there is more of all of those than indoors. When you
perform monthly testing, the mechanical mechanism is less
prone to freezing up due to the accumulation of gunk.
Electronic failure is also exacerbated by outdoor installation,
for the same three factors - heat/cold, humidity and dirt.
Heat harms electronics, temperature changes cause expansion/
contraction, humidity and dirt combine to form resistive
gunk.

Note that I did not mention surges. I do not mean to
say that a surge could not be involved - I just want
to exclude that from the environmental factors I am
talking about.

Install GFCI receptacles indoors to protect the outdoor
receptacles. It is a far better approach. The downside
is that a trip of the GFCI requires a walk inside to reset
it.