track light issues

Discussion in 'Electrical Forum discussion & Blog' started by timbo2000, Mar 9, 2012.

  1. timbo2000

    timbo2000 New Member

    Messages:
    1
    Location:
    Florida
    I'm trying to fix a problem with a track light installment over the a bar I've just put in. I've done it before. never had issues. but this particular problem is driving me nuts. It just defies logic. The electrician who actually installed the associated dimmer switches with this dining room area was called as it seems it may be a flaw with his wiring, but he's blown us off and I have to try and solve this myself.

    This is how it's all set up. I've been rehabbing our home from top to bottom, and converted our old kitchen into a dining area. Within this dining area are four sets of lights, all controlled from one box containing four dimmer switches. I set up all the new wiring and installation of the lights in the ceiling, and we paid an electrician to come in, check everything out, set up the multiple switches, and connect it all to the board. It's all new copper wiring from beginning to end, as I didn't want to connect or splice in to the old aluminum wiring that was in place. All the new wiring and lights are on a dedicated 15 amp breaker. Three of the sets of lights were set up to be available from the day the electrician came around. The fourth, for the track light over the bar, was left hanging from the ceiling capped off and with the switch off, as I still had work to do installing an overhead wine rack, under which the track was going to be set.

    Two days ago I finally got around to putting the track up, but after setting it in place and connecting the power up the lights wouldn't work. I took the lights to out kitchen, where I installed another track light system some time ago, plugged one of the lights in, and it worked just fine. I then went back to the bar area and used a spare track, then a spare connector, to see if I could isolate the fault, yet neither of the items provided a solution. Now here's the weird bit - every time I tried checking the system out, I'd get 120 volts showing from the wiring and from the track when I'd test with the multimeter. But the second I'd put a light into the track, the multimeter would drop to zero on the voltage reading on either the wiring or the track. Take the light fixture back out, and the voltage would pop back up. Inserting the light was thus completing some kind of odd loop. It wasn't just one light - I double checked by grabbing working lights from the kitchen track and inserting them into the other track - the same problem would pop up. Finally, having come to the conclusion that there was nothing wrong with the track at all, I took the whole assembly over to a nearby wall outlet, used some spare electric cable to connect up to the appropriate slots - presto, the light came on! I even double checked all this by grabbing another light fixture destined for our bathroom, and tried connecting it to the wiring over the bar. Nothing. Yet as with the track light, the minute I took it over to the wall outlet and connected it, the light worked.

    So everything logically points to the fact it has to be something to do with this individual circuit, right, because a) the light fixtures work when plugged into another circuit and b) the other three dimmers and lights hooked up in the same box work fine and draw power from the same wire cable/breaker combination. The only things left that I can think of is that the electrician has either wired the dimmer switch up incorrectly or that there's some kind of flaw inside the switch itself. Does this make sense?

    A friend also told me to double-check to make sure that the black wire feeding power to the light was indeed the hot wire, and it is. If I touch it with the black test lead from the multimeter and put the red one to the neutral I show 120 volts. If I keep the black test lead on the black wire and put the red test lead to the ground - I also show 120 volts.

    A final point. I know I'm not overloading the circuit - not even close. With all four dimmers maxed and every light on - including the test light on the track - I'd only be drawing 8 amps on a 15 amp breaker, besides which I'm only using one set of lights while I'm working on this problem anyway. This is a dedicated circuit, so there's no additional power being drawn away from something else.

    So how am I getting 120 volts from this wiring, according to my multimeter, yet it won't light up ANYTHING and keeps giving off the indication that some kind of loop or short is being created every time I actually plug a light into the track? It's got me totally stumped.

    Anyone have any ideas?
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,129
    Location:
    New England
    On a multimeter, the black lead is generally neutral/ground; red is hot/positive, depending on whether it is being used for ac or dc.

    A typical multimeter has a very high input impedance - i.e., it will complete a curcuit, but the impedance or ability to pass current is VERY low, so if you then put a real load on the circuit, where there was high voltage before, now is zero - this is very common, and needs to be taken into consideration when electronic (your dimmer) devices are in the circuit along with the multimeter. IOW, the dimmer may have 120vac on it's hot output when 'off', but it's incapable of providing any current. A light bulb may be in the 10-ohm range depending on it's voltage/wattage rating. Through a multimeter, it may be in the 100,000,000-ohm range or higher, partly so it doesn't unduely load the circuit you are trying to measure, but since it looks sort of like an open circuit, it can 'look' like there's decent voltage/current there when there isn't.

    This is where understanding the tool can be confusing and it can lead to false diagnosis.
  3. drick

    drick In the Trades

    Messages:
    392
    As has already been pointed out, a multimeter is really not a good tool to test 120vac household circuits. Multimeters need a good ground to function properly, and if your problem is with the neutral/ground wire the multimeter has no frame of reference to start reading voltage from (it needs to know what 0 volts is). The voltage displayed will be wrong and you can get all kinds of strange readings. You can also have 120 volts and have no or very limited ability to pass current which sounds like your case.

    It could very well be a bad dimmer or it could be a bad splice such as when you have several neutral wires under one wire nut (such as when you have a group of switches in one box all on the same circuit). In the bad splice case you could have a neutral wire that is barely making contact - and because it is under a wire nut with several other wires it tends to go unnoticed during installation. It can pass a miniscule amount of current - enough current to give you an accurate reading on your multimeter -but the second you put a load on the wire it is pulled down to 0 volts.

    -rick
  4. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    I don't agree with that at all. Multimeters are the PROPER tool to test with. Simple test lights or beepers are much less limited in scope. I don't know how a multimeter requires a ground.

    The key point was pointed out by jad.....you have to understand the circuit in order to understand how the multimeter interacts with the circuit, in order to interpret the readings. EVERY reading tells you something. Reading 120 tells you something. Reading 60 or 0 also tell you something. But no reading helps unless you understand the circuit. Every reading will be a clue to what is right, or what might be wrong.....
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,815
    Location:
    Cave Creek, Arizona
    If it is all new wiring, the problem has to be the dimmer connection to hot, the light's connection to the dimmer, or the neutral wire. Connect the light, turn on the switch, which apparently gives you zero voltage across the wires, then test from the light 'hot' to a ground source. If it is 120v then the problem is the neutral, if it is stll zero then it is the hot connection that is bad.
  6. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    We haven't mentioned this: are you trying to dim either fluorescent or led bulbs???? Trouble in river city.
  7. ActionDave

    ActionDave Electrician

    Messages:
    351
    Location:
    Colorado
    I didn't read all of the OP. I tried but I could't get through it, but based on some of the comments the problem could a weak connection.

    I would check with an analogue meter or a wiggy.
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