Hi Jeff!

JW barry martin wrote:
JW
JW Ernie:
JW
JW E& I have a strange problem here. Light fixture suddenly does not work.
All
JW E& bulbs OK, of course. I assumed it was a bad switch, which I replaced
ith
JW E& no change.
JW E&
JW E& I checked line voltage at the switch........it is fine, 122V. However
at
JW E& the fixture, there are only 75V! Not enough voltage to operate the fi
tur
JW
JW E& bulbs. Why am I losing so many volts, and how to correct?
JW
JW There's an open somewhere. I'm assuming the fixture in question uses
JW an incandescent bulb rather than fluorescent and the replaced switch
JW was in the fixture. This means the open is probably somewhere between
JW the plug and the switch, more than likely at th plug itself. Possibly
JW failed because the plug was bent at a right angle by furniture.
JW
JW Note: it may be cheaper to buy an extension cord and cut the socket
JW end off than to buy a length of wire with plug.
JW
JW
JW I'm interested in your reasoning there Barry.
JW
JW If the OP said he had 122V "at the switch", and you assumed that what he
JW called a "light fixture" was just a lamp, with the replaced switch in
JW it, then why would you blame the cord, which is *ahead* of the switch?

Good point! For some reason I'm presuming a table lamp and you a
hard-wired permanent fixture. In rereading the original post you are
probably more correct in the guess -- some details were left out (or
at least I'm not seeing them.

And yes, you are correct: if there is voltage at the switch the would
have to be voltage in the plug. (Here brain! Come here, brain!)


JW I'll bet the "light fixture" is on a ceiling or wall, and the switch is
JW a wall switch. He's probably getting that 75 volt reading because he's
JW using a sensitive digital meter, the return (white) wire from the
JW fixture has a break in it somewhere, and he's seeing that 75 volts fed
JW through the capacitive reactance of the wiring.

I've got to practice more with my DVOM. Usually when there is a
problem like that I've used the (old) analog meter, I guess partially
because it is old (won't feel so bad if I fry it or drop it) and
because I know a DVOM can give false readings.

-
¯ barry.martinþATþthesafebbs.zeppole.com ®

* He who steals my taglines is seriously lacking in taste!
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þ RIMEGate(tm)/RGXMod V1.13 at BBSWORLD *

On 21 Feb 2004, barry martin wrote:

I've got to practice more with my DVOM. Usually when there is a
problem like that I've used the (old) analog meter, I guess
partially because it is old (won't feel so bad if I fry it or
drop it) and because I know a DVOM can give false readings.

IMHO, the biggest problem *by far* with digi meters is the
tendency for the user to overlook the (usually) tiny little
lightup of "mV" when they're taking a voltage reading.
People think they have 45 or 60 -volts- while they're actually
seeing a (normal) small amount of milivolts.

Not necessarily saying that's *you*, by any means!

--
No more big'uns for me, now I'm a 'Venture Capitalist'.
I've learned to totally appreciate 'Small Firms'.

Hi Ernie!

ED Yes, I am talking about a wall mounted dimmer switch which controls a
ED ceiling mounted light multi-light fixture.
ED
ED When I check voltage coming into switch, it is 122V. When I turn the dimme

ED switch off and check voltage at wiring into fixture, I get 0 volts. When I
ED turn the switch on, it reads initially at 70V, then quickly lowers to a
ED reading of 50V.

Not sure why the 20v drop. Sort of sounds like a problem with the
dimmer but you said you replaced it in the original message.


ED Of course, I am checking fixture input V with the dimmer switch at multiple
ED positions, but makes no difference.

What about checking voltage at the output of the dimmer?


ED Does all this just sound like an open circuit in the white? That would be

ED real problem, since allthis wiring is behind finished walls.

The good news is usually the break is in the junction box, not in the
middle of the run. I'd be inclined to check for a broken wire where
the insulatation was stripped: wire was nicked and broke. It's
possible a wire pulled loose from a wire nut. Hopefully it's
something simple.

-
¯ barry.martinþATþthesafebbs.zeppole.com ®

* Definition: Tendon - Taking care of business
---
þ RoseReader 2.52á P003186
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---
þ RIMEGate(tm)/RGXMod V1.13 at BBSWORLD *

IM I've got to practice more with my DVOM. Usually when there is a
IM problem like that I've used the (old) analog meter, I guess
IM partially because it is old (won't feel so bad if I fry it or
IM drop it) and because I know a DVOM can give false readings.
IM
IM IMHO, the biggest problem *by far* with digi meters is the
IM tendency for the user to overlook the (usually) tiny little
IM lightup of "mV" when they're taking a voltage reading.
IM People think they have 45 or 60 -volts- while they're actually
IM seeing a (normal) small amount of milivolts.
IM
IM Not necessarily saying that's *you*, by any means!

laff No, not me!!! gg Good point on overlooking the 'mV' detail.
I've sort of developed a (for lack of a better term)
"logical/illogical" thought process. If I were to test a light on a
120v circuit I'd expect around 120v when there is power present and 0
when not. Anything else is "not logical", especially 45 or 60 volts.
(We're discounting dimmers, etc., here.) Also if there really was ~50
volts present with an incandescant bulb the bulb should be partially
on. The 'logical' thing to do is to check for a reading error. ...Of
course part of the 'problem' is the newbies haven't had time to
learn/experience these truisms.

Must admit the first time I used an autoranging DVOM it scared me a
little: wha'd'ya'mean I plug the probes into 120vAC after testing a
9vDC battery and it 'knows' and won't fry?!

-
¯ barry.martinþATþthesafebbs.zeppole.com ®

* Don't frown. You never know who is falling in love with your smile.
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þ RoseReader 2.52á P003186
þ The Safe BBS þ Bettendorf, IA 563-359-1971
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þ RIMEGate(tm)/RGXMod V1.13 at BBSWORLD *