thomas rush wrote:

[First -- I didn't see a better group to post this
question... if one exists, I'd appreciate a pointer...
but I've found that this group will deal with almost
any electrical issue!]

Hi, all.

I've got a problem with my home electical system, and
was hoping to get a pointer from the group before I
scheduled a service call.

Setting:
A 10-year-old house in the US with standard 110
wiring, no known electrical or wiring problems
before this. Home is currently vacant, but
everything worked when my family and I were living
there with all the normal drains of computer,
microwaves, electonics, refrigerator, A/C....

What's happening:
I noticed a few days ago that the first floor A/C
system did not seem to be cooling, but I didn't have
time then to check it out. When I went back to
investigate yesterday, I found that the unit blower
would be on but the air wasn't coming out cold.

I noticed an unusual dimming of the living room
lights when the A/C unit came on -- not just a
temporary dip-then-back-up, but a noticeable drop
to maybe 2/3 brightness that didn't come back up
again.

I checked and all circuit breakers seemed to be
set -- but I flipped them off and reset them to
'on' anyway. Back in the house, when I turned
the A/C unit back on, the same bank of lights
that dimmed before with A/C operation (living
room et al.) now wouldn't come on at all! They
did eventually come back on, but it was after I
went outside to reset the single-throw breakers,
and I believe it took several minutes even after
I turned the A/C off (these are standard
incandescent bulbs, not fluorescent or halogen).

I went in to the attic and didn't see anything
strange with the heater/AC blower unit, fwiw.
I believe that the HVAC system is on a separate
circuit from the 110v circuits that feed the
lights in the house.

Puzzled and without a flashlight to see in to
the breaker box or look at the outside cooler
enclosures (the grills with fan in the center), I
turned the HVAC system off at the thermostat
and left.

Questions:
I'm a bit confused by the behaviour of the lights,
which have never acted this way before. What
would the group's guesses be as to cause? Is it
possible that it is just a breaker is going bad?
What would you do as next steps?

I appreciate your suggestions.



The central A/C should be 240v, you can verify this by looking at the
breaker for it, which would be double pole, usually there's two separate
levers connected with a bridge though some have a single lever on a
double wide body. If that's the case, I suspect one whole side of the
panel may have a poor connection, take the cover off and look at the
heavy wires coming in at the top where they connect to the main and
touch the insulated portion near the main breaker to see if they're
warm. A common problem here is the lugs work loose and you get a poor
connection, but it could also be outside in the sealed meter box, where
the wires splice at the weather head (if overhead wiring), or out at the
transformer on the pole or in a box, the latter of which you'd need to
call the utility, if it's on their side of the meter they'll fix it for
free. If the lugs in the panel are loose, you can carefully use a
screwdriver to tighten them, being sure to only touch the plastic
handle, wearing gloves is a good idea too. I normally check mine every
few years just to make sure since we had a meltdown in the service panel
of the house I grew up in because of that.