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Todays Puzzler.The mystery of electricity

J

j

Jan 1, 1970
0
The spare bath in my house was added in the '60s. There is a fixture
over the sink with a double light socket, one faces left and one faces
right,it's one piece. Common at one time.

So today I wanted to put a fan in this otherwise unused bathroom. I got
an edison base adapter and screwed it in one of the sockets. Plugged in
the fan and nothing. Didn't matter how it was switched. So I went off to
get a bulb to test the other socket. When I screw in the bulb, it does
not light but the fan goes on. The fan seems to be fine and the bulb is
completely dark. Unscrew the bulb and the fan turns off.

WTF!

Who cares to gamble a wild ass guess?

Obviously the fixture has to go! But very strange.

Jeff
 
B

Bob F

Jan 1, 1970
0
j said:
The spare bath in my house was added in the '60s. There is a fixture
over the sink with a double light socket, one faces left and one faces
right,it's one piece. Common at one time.

So today I wanted to put a fan in this otherwise unused bathroom. I
got an edison base adapter and screwed it in one of the sockets.
Plugged in the fan and nothing. Didn't matter how it was switched. So
I went off to get a bulb to test the other socket. When I screw in
the bulb, it does not light but the fan goes on. The fan seems to be
fine and the bulb is completely dark. Unscrew the bulb and the fan
turns off.
WTF!

Who cares to gamble a wild ass guess?

Obviously the fixture has to go! But very strange.

Maybe you have a 220V circuit with 2 110V bulbs wired in series.
 
J

Jim Wilkins

Jan 1, 1970
0
j said:
The spare bath in my house was added in the '60s. There is a fixture
over the sink with a double light socket, one faces left and one
faces right,it's one piece. Common at one time.

So today I wanted to put a fan in this otherwise unused bathroom. I
got an edison base adapter and screwed it in one of the sockets.
Plugged in the fan and nothing. Didn't matter how it was switched.
So I went off to get a bulb to test the other socket. When I screw
in the bulb, it does not light but the fan goes on. The fan seems to
be fine and the bulb is completely dark. Unscrew the bulb and the
fan turns off.

WTF!

Who cares to gamble a wild ass guess?

Obviously the fixture has to go! But very strange.

Jeff

Maybe the torque on the bulb wiggles a poor connection.

jsw
 
W

Winston

Jan 1, 1970
0
Bob said:
j wrote:
(...)


Maybe you have a 220V circuit with 2 110V bulbs wired in series.

I concur with your diagnosis, Dr.

Except that the 'cold' resistance of an incandescent
bulb would pass plenty of current to power a series-
connected fan in a ~120 V circuit.

--Winston
 
B

Bob F

Jan 1, 1970
0
Winston said:
I concur with your diagnosis, Dr.

Except that the 'cold' resistance of an incandescent
bulb would pass plenty of current to power a series-
connected fan in a ~120 V circuit.

Which is what he said it does.
 
A

amdx

Jan 1, 1970
0
Maybe the torque on the bulb wiggles a poor connection.

jsw
That's also my guess, when the bulb is screwed in it compresses
a connection in the socket.
Mikek
 
V

Vaughn

Jan 1, 1970
0
The fixture is probably ok, just miswired. I gather you haven't been
using it, since you had to fetch a bulb for testing.

I suppose it may have been miswired on purpose--to provide softer light,
particularly for late night visits.

The above explanation sounds more likely than the 240-volt guess.

I also like soft light in a bathroom. I choose slow-starting CFLs these
days. Guys shouldn't try to pee in the dark, but full-bright light is
piercing when you get up in the middle of the night.

Vaughn
 
W

Winston

Jan 1, 1970
0
Bob said:
Winston wrote:
(...)


Which is what he said it does.

Yup. As Gary Heston points out, the series connection
might have been on purpose.

--Winston
 
J

Jim Wilkins

Jan 1, 1970
0
Winston said:
Yup. As Gary Heston points out, the series connection
might have been on purpose.

--Winston

Easily checked with two bulbs of different wattage.

jsw
 
W

Winston

Jan 1, 1970
0
Jim said:
(...)


Easily checked with two bulbs of different wattage.

Yup.

Though, personally I'd want to shut off the supply and
open the fixture box to determine what other surprises
lay in wait. :)

--Winston
 
J

j

Jan 1, 1970
0
On 5/31/2012 4:06 PM, j wrote:

I took apart the fixture today and found out why. Let's review the
evidence:
The spare bath in my house was added in the '60s. There is a fixture
over the sink with a double light socket, one faces left and one faces
right,it's one piece.

Note the "one piece".
Common at one time.

So today I wanted to put a fan in this otherwise unused bathroom. I got
an edison base adapter and screwed it in one of the sockets. Plugged in
the fan and nothing. Didn't matter how it was switched. So I went off to
get a bulb to test the other socket. When I screw in the bulb, it does
not light but the fan goes on. The fan seems to be fine and the bulb is
completely dark.

Note that the fan worked fine, it's not that it struggled on partial
voltage, and if it was wired in series, the bulb (an incandescent) was
completely dark.

This removes the series connection theories. And certainly the 220v
theory that depended on it.

So, what we have in the socket in the dead middle is a U shaped flat
copper strip. The hot wire is soldered to this and each end of the U
contacts a bulb center contact. For the ground threaded part: there are
two of these with a solder tab. They are facing outward, of course, but
the tabs are together and the ground wire is soldered to the left socket
that had the bulb screwed in. The tabs are in turn soldered to each other.

So, what happened?

The connection between the two tabs broke apart. When the bulb was
screwed in it pushed it's ground tab out enough to contact the other tab
and send power through it's "ground" connection.

The winner is: Jim Wilkins

Why didn't the bulb light? The "hot" contact was oxidized enough to be
an insulator.


I have pics and video...

Jeff

Unscrew the bulb and the fan turns off.
 
W

Winston

Jan 1, 1970
0
j said:
On 5/31/2012 4:06 PM, j wrote:

I took apart the fixture today and found out why.

Thanks for closing the loop, j.
Well done, Jim.

--Winston
 
B

Brian Gaff

Jan 1, 1970
0
Sounds like someone has done my favourite trick to make bulbs last
indefinitely and put them in series.
Brian
 
J

Jim Wilkins

Jan 1, 1970
0
j said:
...> The connection between the two tabs broke apart. When the bulb
was screwed in it pushed it's ground tab out enough to contact the
other tab and send power through it's "ground" connection.

Bad grounds and intermittent connections cause the oddest symptoms.

In Army Signal Corps electronic school the instructors doctored AGC
glass fuses to remind us to check them with a meter, not just by
sight. They heated one end cap to melt the glue and pop off the cap,
then inserted too-short heavy bus wire and even blue ("the fuse blew")
paper to make it look good again. I caught the 1 Amp fuse with 12 AWG
wire inside it visually and went up to joke with the instructor about
it, then we watched most of the class pull out the phony fuses, give
them a puzzled look, put them back and continue troubleshooting.

jsw
 
M

m II

Jan 1, 1970
0
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Hash: SHA1

Jim said:
Bad grounds and intermittent connections cause the oddest
symptoms.

In Army Signal Corps electronic school the instructors doctored AGC
glass fuses to remind us to check them with a meter, not just by
sight. They heated one end cap to melt the glue and pop off the
cap, then inserted too-short heavy bus wire and even blue ("the
fuse blew") paper to make it look good again. I caught the 1 Amp
fuse with 12 AWG wire inside it visually and went up to joke with
the instructor about it, then we watched most of the class pull out
the phony fuses, give them a puzzled look, put them back and
continue troubleshooting.


Fuses on electric stoves/ranges are bad for that. They commonly break
the link where it bends, just outside of sight. The fuse looks good
through the glass, but there's no continuity.

The repeated cycling off/on and the resultant thermally caused
expansion/contraction probably work hardens the metal where it's
already been stressed by the bend, causing the fractures.

So, yes...using a meter is a very good idea.


mike






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V

Vaughn

Jan 1, 1970
0
Bad grounds and intermittent connections cause the oddest symptoms.
Yes, I learned the hard way. Early in my career, I spent two days
trying to troubleshoot a simple problem with the tail lights on a pickup
truck. They had the oddest symptoms! My meter seemed to be of no help,
giving all kinds of strange readings. In the end, it totally defeated me!

In desperation I took the truck to a dealer. They said "No problem!"
When I got it back, I discovered that they had installed a ground wire
between two certain frame members under the truck, which totally cleared
up the problem. They had probably seen dozens with the exact same issue.

Vaughn
 
J

j

Jan 1, 1970
0
attention, the new fan should really be on a GFCI circuit. Which
doesnt sound like it is from the OPs description.....


It is now. It's an unused bathroom with the water off. I wanted a fan in
the window and there are no outlets. I ran an extension over to a
kitchen outlet.
Incidently I replaced all the wiring on a trailer, and had never done
anything like it before. I had my friends box trailer in my driveway
for a few days. I completed the rewire and was very proud when she
came to pick it up.... only problem the lights didnt work.....


traced to a bad ground wire in her nearly new ford commecial van.....

i leared a lot fom that volunteer job....

I was in the audio biz at one time and grounds are all important.

As far as vehicles, grounds are always suspect.

If you clip your volt meter on to a known good ground, and have
everything "on", then you should have near zero volts at other grounds
you test.

It's easier/faster to test volts than resistance. Testing resistance
when you have clear suspects.

Of course, common problems become known after a while. But, I'm at
the stage in my life that I never want to have the same problem more
than once.

Jeff
 
V

Vaughn

Jan 1, 1970
0
If you clip your volt meter on to a known good ground, and have
everything "on", then you should have near zero volts at other grounds
you test.

It's easier/faster to test volts than resistance.

Yep! That's exactly what I do. I've found zillions of bad connections
with a voltmeter. It's just a simple application of Ohm's law.

Vaughn
 
M

Mho

Jan 1, 1970
0
Stick with your failed Internet business.

------------
"m II" wrote in message Fuses on electric stoves/ranges are bad for that. They commonly break
the link where it bends, just outside of sight. The fuse looks good
through the glass, but there's no continuity.

The repeated cycling off/on and the resultant thermally caused
expansion/contraction probably work hardens the metal where it's
already been stressed by the bend, causing the fractures.

So, yes...using a meter is a very good idea.


mike
 
T

The Real Bev

Jan 1, 1970
0
When did 3AG fuses become AGC? Serious question...
 
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