I have a dimmer switch installed for the bathroom light at my cottage.
The light fixture itself has 6 small 25W lightbulbs. For the past three
years, the dimmer has worked perfectly. Three weeks ago the dimmer
stopped dimming and could only be used to switch on and off. I replaced
that dimmer with a similar (inexpensive) switch that worked quite well
for three weeks - then the same thing happened - the switch was blown
and would only turn off and on. This weekend I replaced the second
blown dimmer with a more expensive ($20) dimmer. It worked long enough
to show my wife how brilliant I was, and then stopped altogether. I
replaced it with a normal switch for now.

I suspect two things - a short in the light fixture or a short in the
wiring. On my next trip up to the cottage I plan to replace the light
fixture with a simple fixture and install a (cheaper) dimmer to see if
it the fixture that is causing the issue.

Any thoughts or advice on
1) what could cause the dimmer to fail after working fine for 3 years?
2) how will I be able to identify if there is a short in the light
fixture (ie what do I look for)?
3) how can I determine if there is a short in the wiring?

Thanks!

wrote in message
ups.com...
I have a dimmer switch installed for the bathroom light at my cottage.
The light fixture itself has 6 small 25W lightbulbs. For the past three
years, the dimmer has worked perfectly. Three weeks ago the dimmer
stopped dimming and could only be used to switch on and off. I replaced
that dimmer with a similar (inexpensive) switch that worked quite well
for three weeks - then the same thing happened - the switch was blown
and would only turn off and on. This weekend I replaced the second
blown dimmer with a more expensive ($20) dimmer. It worked long enough
to show my wife how brilliant I was, and then stopped altogether. I
replaced it with a normal switch for now.

I suspect two things - a short in the light fixture or a short in the
wiring. On my next trip up to the cottage I plan to replace the light
fixture with a simple fixture and install a (cheaper) dimmer to see if
it the fixture that is causing the issue.

Any thoughts or advice on
1) what could cause the dimmer to fail after working fine for 3 years?
2) how will I be able to identify if there is a short in the light
fixture (ie what do I look for)?
3) how can I determine if there is a short in the wiring?

Thanks!


If there was a short the circuit breaker would have tripped. I've seen this
happen before where a dimmer burns out for no apparent reason. Check to
make sure all of your splices in the switch box and the light fixture are
tight. I'm guessing that the light fixture has gotten a little old and the
sockets are generating excessive heat and possible arcing. Might be time to
replace it with a new one.

Is there any thing else on this circuit such as receptacles with a heavy
duty appliance plugged in?

Good to know about the breaker - it makes troubleshooting this a bit
easier. I've checked the splices in the switch box and they are good.
There are two outlets on the same circuit - one has a lamp plugged in
and the other has nothing plugged in. I will check the connections in
those boxes to make sure they are good as well.
I suspect it is the light fixture - I will replace it this weekend and
see what happens. Thanks for the reply!

On 23 May 2006 17:02:30 -0700, wrote:

I have a dimmer switch installed for the bathroom light at my cottage.
The light fixture itself has 6 small 25W lightbulbs. For the past three
years, the dimmer has worked perfectly. Three weeks ago the dimmer
stopped dimming and could only be used to switch on and off. I replaced
that dimmer with a similar (inexpensive) switch that worked quite well
for three weeks - then the same thing happened - the switch was blown
and would only turn off and on. This weekend I replaced the second
blown dimmer with a more expensive ($20) dimmer. It worked long enough
to show my wife how brilliant I was, and then stopped altogether. I
replaced it with a normal switch for now.

I suspect two things - a short in the light fixture or a short in the
wiring. On my next trip up to the cottage I plan to replace the light
fixture with a simple fixture and install a (cheaper) dimmer to see if
it the fixture that is causing the issue.

Any thoughts or advice on
1) what could cause the dimmer to fail after working fine for 3 years?
2) how will I be able to identify if there is a short in the light
fixture (ie what do I look for)?
3) how can I determine if there is a short in the wiring?

Thanks!

Just so you know, they make the standard dimmers for 600 watt maximum,
but they sell heavy duty or industrial ones in the 1000 and higher
wattages.

Just curious, is this in a metal or a plastic box? Metal boxes help
dissipate the heat from the dimmers faster. Heat is what kills them.
Better to use a metal box, and always tighten the screws directly to
the metal. DO NOT leave those little cardboard or plastic holders on
the screws. A metal switch cover (plate) will also help cool them.

Mark

wrote:

I have a dimmer switch installed for the bathroom light at my cottage.
The light fixture itself has 6 small 25W lightbulbs. For the past three
years, the dimmer has worked perfectly. Three weeks ago the dimmer
stopped dimming and could only be used to switch on and off. I replaced
that dimmer with a similar (inexpensive) switch that worked quite well
for three weeks - then the same thing happened - the switch was blown
and would only turn off and on. This weekend I replaced the second
blown dimmer with a more expensive ($20) dimmer. It worked long enough
to show my wife how brilliant I was, and then stopped altogether. I
replaced it with a normal switch for now.

I suspect two things - a short in the light fixture or a short in the
wiring. On my next trip up to the cottage I plan to replace the light
fixture with a simple fixture and install a (cheaper) dimmer to see if
it the fixture that is causing the issue.

Any thoughts or advice on
1) what could cause the dimmer to fail after working fine for 3 years?
2) how will I be able to identify if there is a short in the light
fixture (ie what do I look for)?
3) how can I determine if there is a short in the wiring?

Thanks!

Any lightning strikes or possible power surges in your cottage's area?

You might want to consider installing a "whole house" surge arrestor
across the incoming power line at the breaker box.

A 150 watt load isn't much for a dimmer like that, but perchance did a
bulb burn out at the same time as the dimmer failed?

Bulbs can burn out with a "tungsten arc" effect which produces a very
short high current spike which can fry solid state devices like dimmers.
You can prevent that by wiring a 2 amp "fast blow" 3AG fuse in an inline
fuseholder in series with the fixture. Then, if a bulb goes with a
tungsten arc the 25 cent fuse will blow and save the dimmer.

HTH,

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"Life is like a sewer -- what you get out of it depends on what you put
into it."

According to John Grabowski :

If there was a short the circuit breaker would have tripped.

A moderate-to-heavy short on the load side of a dimmer tends to fry
the dimmer before the breaker has time to notice.

Silicon devices (eg: the triacs in dimmers) make _very_ _very_
fast fuses.

An momentary arc (bad lamp bases) might be the problem.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.

Quite right.

The dimmer is rated at 600W and the breaker at least 15A. Anything
between these will fry the dimmer and not bother the breaker.

RickR

This past weekend I replaced the light fixture and replaced the dimmer
switch with a new dimmer. Everything has worked fine. I believe it must
have been a short somehwere in the light fixture causing the issues. I
appreciate the suggestions and the assistance.

I don't know about previous postings,
however, I have seen a lamp burn
out rather violently creating a
momentary short, which in turn, takes out
the dimmer. Now this was a number of
years ago. I think newer dimmers
are built a little more robust.

wrote:
This past weekend I replaced the light fixture and replaced the dimmer
switch with a new dimmer. Everything has worked fine. I believe it must
have been a short somehwere in the light fixture causing the issues. I
appreciate the suggestions and the assistance.

According to RickR :
Quite right.

The dimmer is rated at 600W and the breaker at least 15A. Anything
between these will fry the dimmer and not bother the breaker.

And a heavy short in excess of 15A will fry the dimmer before
the breaker notices. Breakers are very slow compared to the
overheat time of a silicon junction.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.