Wiring problem- light fixture detects power but bulbs don't light?

Question

I confirmed the bulbs work and that the light bulb sockets in the fixture detect electricity when switch is on (and none when switch is off). I have tried flipping the breaker to reset everything but still nothing works. I have tried rewiring my switching to confirm good connections.

Why are my lights not lighting up??

Answer 1

Just for the heck of it try unplugging the light and cleaning the inside brass threads with steel wool.  Maybe its oxidized and the bulb is not making contact. also clean the bottom tab.  Using a voltmeter with a sharp point may have been able to push through the oxidation and give you a reading. Good Luck

Answer 2

First of all, safety.

Unplug everything.

Now, with your multimeter set to OHMS (resistance), put to the smallest scale possible, probably your multimeter has a 200 ohms scale.   One lead of the multimeter to the metal part of the lamp socket that has threads, that contact the large metal of the lamp.  The other multimeter lead goes to any one of the two prongs at the end of the wire that normally goes to the power outlet at the wall. Some fixtures present a wider or fatter prong, that should be the one.  If the meter does not show very close to ZERO reading, change the lead to the other prong at the end of the wire.   One prong SHOULD present very close to ZERO ohms of reading.  That part of the lamp socket is the "neutral" side of the power, it should have a direct connection to the fatter pin on the connector at the end of the wire.  

Well, if it presents ZERO ohms, at least 50% of the connection is ok.

Second, move the first multimeter lead to the center pole at the lamp socket, and the second lead to the other pin of the power plug.  If it does not show ZERO ohms, turn the lamp switch, now it must show ZERO ohms, if not, something is bad between the two points you are measuring.

If both measurements shows ZERO ohms, then measure the resistance of the lamp (if incandescent), probably you will need to switch the multimeter k**b to 2000 (2k) ohms or so, a 40W lamps should present something around 100 ohms or so when cold, around 300 ohms hot (you will not want to measure it hot).  

If everything goes ok, and the lamp still not turning on, there may be some bad contact inside the lamp socket.

You can clean it up, but do it with power cord removed, and make sure to clean any metallic debris that may end up inside the socket before you try to power it up again.

Answer 3

What do you mean when you say that the "fixture detects electricity"?  Are you using a voltmeter to check across the center contact and the outer threaded shell and get a reading of 115-120 V.  AC? If, that is so, then there HAS to be something that is causing the bulbs you have certified to be good, not to be able to being screwed in far enough for the center contact points to meet.

Answer 4

Simple, the neutral (Return) leg of the light is open. Look for a broken wire in the fixture, the outlet or the power cord.  Otherwise, call a qualified professional electrician.

   Are you using a digital meter?  They will read voltage when it is not present.  Get an analog device that will tell the truth.

Answer 5

Hmm that's a tuffy.  The others seem to have covered the likely culprits.

The threaded socket shell is attached to the base with two rivets.  One of these rivets is the connection to the neutral wire in the socket.  Maybe the rivet is pulled loose or the shell is damaged and when a lamp is screwed in it pulls the shell away enough to lose contact but restores the connection when the lamp is removed.

Just another 2 cents...

Answer 6

I have encountered this with outside Christmas lights.  Not sure if it will help you but here it is.

In the socket at the bottom there is a tab, sometimes it can be pressed down enough not to spring back up.  In this case I use a plastic tool similar to what a dentist uses to scrape teeth with to pull it up about an 1/8 of an inch.

Other times, depending on the socket, the side instead of being metal all the way around will have only a metal strip and it may not be making good contact.  I use the same tool to pull it out enough to touch the threaded portion of the bulb.

Also, compare the bulb you are putting in to another bulb currently in use and make sure the threaded parts are the same length.  I suppose that part could be too short.

Answer 7

sounds like a bad transformer.