testing light circuits exterior lights?

Question

I have recently replaced blown bulbs on the two front exterior lights in the lantern on the front of my house. The lights still do not work, and there is no problem with the circuit breaker. how can i test the wiring (visual inspection looks okay) - I have a multimeter but im not an electrician so not sure exactly where to test.

Answer 1

"im not an electrician" ... then for your own safety, get an electrician in.

Answer 2

I think there may be something more going on.

Case A: You Never Saw Light There Before

First, two bulbs don't die together. Have you ever seen light on these bulbs? If you recently moved in or have only found time to replace light bulbs which never worked since you moved in, let's suspect the simplest explanations:

1. Maybe these light bulbs are connected to motion-detector and/or day/light sensor. Many security lights are. If they are, you may have to wait for night, move around motion detector (whereever it may be), and see if they come on.

2. There is probably an internal switch to turn on (and off) these lights which may be off.

By the way, did you test the light bulbs you took out (that you suspect are dead). Are they really dead?


Case B: Light Bulbs Died One By One

If you had the lights on, and saw one die, and the other die after a long time, then here's what you can do:

Multimeter:
Make sure you have the probes at the correct place

(red plug on V, possibly VAC, possibly 200 V / 300 V / 600 V if there is a separate place for AC or high-voltage measurements)

Use maximum AC voltage setting (200/300/600; make sure it's higher than your city voltage).

Know that if you let the probe slip and touch two sides at the same time a spark will fly, an arc will form and char the metal, may melt things around it, and scare you. Yes, I have done this many times before. Be very steady when you touch the connections. Look at multimeter screen but look right back at your connections (don't look away for too long because you'll forget to focus on the probes).

Now: Take out the light bulb and check the AC voltage in the socket (between inner side and back bottom point). It should be your city voltage (120 V in the US, 230 V in the UK).

1. If the voltage is OK: The light bulb does not go in all the way to touch the bottom of the socket. Tighten it (without breaking). If it just doesn't work, maybe your light bulb has too short a tip.

Maybe you can try the light bulb elsewhere (on an indoor socket that can handle this much power): Does it work? If you can't try it elsewhere, just use ohmmeter (at low, 100 ohm or 200 ohm setting) in multimeter, and connect the probes to the light bulb (not socket!); the multimeter should show some resistance (a light bulb may have 5 ohms, 10 ohms, much less or much more; actual resistance doesn't matter for us) rather than OL (which means open circuit).

Now, turn the multimeter back to volt measurement before you forget. If you use ohmmeter and connect probes to city voltage, you'll fry your multimeter (rather, fry the fuse inside it; more recent non-$15 multimeters have harder-to-get fuses for which you may have to wait till it is shipped to you).

2. If the voltage is significantly less but not 0: This shouldn't happen unless you have a half-dimmed dimmer connected to this external socket (which would be a weird thing to do).

3. If the voltage is 0: Back to square 1. The circuit breaker, any line, any switch along that line, any motion detector or day/light sensor could be to blame.


Some Bad Ideas:

As you don't yet have much experience with electricity and multimeters, let me remind you that it is not safe for you to try to:
Cut the line at any point: you can die
Push things inside the wire to find out the voltage/current/continuity: You can die!
Attach patch wires to your wires: STOP! YOU CAN DIE! HELLOO?

I'm sure you heard me loud and clear right there.

If simple tests don't help you, ask a friend who has experience to come help (and teach you in the process), or call an electrician.

Answer 3

Sometimes a bulb will go short-circuit just before it blows. This can damage other circuit components like switches and lampholders.

Remove each bulb and check that you have 230v at the pins of the socket.
If the volts are not there then it's possible that the switch is faulty.

If this simple check doesn't find your fault then you should call in an electrician. Exterior circuits are one of the restricted items under the new part P of the Building Regulations and their management is described in the Wiring Regs.

NOTE.
Unless you're in the USA (in which case you shouldn't be on the UK&I site) please ignore the emdog answer. American wiring specifications are very different from ours and trying to follow that advice could be lethal.

Answer 4

Well I'm assuming here that this light is mounted to the house and not a pole light where there would be underground wiring .
Take the light apart and test the wiring to the light first Just uncap the wires,turn the switch on and touch one probe each to the white and black wires.If there is power then you know 2 things The light is ok and the switch is ok No power could indicate a problem with the switch.
P.S.My answer assumed you are working with 120V If you are in the UK Don't listen to me.Although why anybody would want to put 230V to a simple light is beyond me.Of course I've only been doing home remodeling for 15 years so i guess I haven't seen everything yet....lol

Answer 5

USA answer only. Ignore if you are not in the US.

Set the meter for 120 or more AC volts. Pull out the light switch from the wall and turn it on. Test from the bottom screw to ground or neutral. Test from the top screw to ground or neutral. 120 volts on one and not the other means the switch is bad. No voltage on either screw means you need to look ahead of the switch to where it is fed from. Keep checking power back to the circuit breaker. Or continue on to check the light fixture. Measure voltage from the center contact to the shell. Be careful. Wear safety glasses when testing with the power on. Email if you need more help.

Answer 6

A multimeter usually comes with instructions, best to follow the guidance contained therein, If replacement proven bulbs do not light sounds like no power to the fitting.

Answer 7

Erndogs advice is dangerous, I'm sure he said it as a joke, but unfortunately someone like you who has no idea about electricity could follow his advise and end up dead, not what you want I'm sure. Best advice i can give you is forget about the multi meter and buy a power tracer, this will tell you where you have a live feed without touching any wires, if this fails to trace the fault, then i would suggest you call an electrician in, for everyone safety.

Answer 8

I wouldn't use a multimeter, but a voltage tester would be more suited. If these are halogen floodlights, and the lamp had def. failed then you have probably not put the new lamps in correctly. Go back and make sure that it is sitting straight and is seated on BOTH the button contacts. If ES lamps, make sure they are screwed down properly.
Did both lamps stop working together, are they controlled by one or two switches or a photocell or PIR?????

Answer 9

If the lamps are halogen make sure they are in the lampholders properly at both ends as its easy to put them in wrong. Did you touch the glass of the lamps? If you did this can damage halogen lamps. For your own sake forget the multimeter.

Answer 10

if you dont have a good insight into electricity i surpose you call an expert.
that person will find out if any of these happened: 1 burnt cablles. 2 inline cable bridging etc