Troubleshooting......... Phantom voltage????

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Hi. I am new to this site. I have been reading threads on here for years but never contributed till now. This is the second time I ran into this problem in the past six months. After disconnecting knob and tube wiring from a single pole single throw switch. I am reading 122 volts on (a Sperry 540 multimeter) between the hot wire entering the junction box and the load wire going to the light. these 2 wires are the only 2 wires in the JB. The old switch was working fine but the customer wants to update to a dimmer. When I touch the 2 wires together the fixture lights turn on with no problem. I installed the dimmer and it works fine but obviously no ground. I just don't feel right walking away from that weird voltage reading. I've seen phantom voltage readings before but never so high and never between the line and load of a switch. This happened to me about six months ago but that time I was using a Fluke 325 Multimeter and the 119 volts was at a 3way switch between one of the travelers and the point wire going to the light fixture. None of the fixtures involved had ballasts.......any thoughts...Thank You.
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
I am reading 122 volts on (a Sperry 540 multimeter) between the hot wire entering the junction box and the load wire going to the light. these 2 wires are the only 2 wires in the JB.

Maybe I am misunderstanding, but this sounds absolutely normal to me. You will always read full voltage across any open switch through a load.
 

electricalist

Senior Member
Location
dallas tx
Sometimes the switching is done with the neutral and you are opening the neutral when you turn the switch off.
Be carefull the load may be present and waiting for a path.
 

kwired

Electron manager
Location
NE Nebraska
Hi. I am new to this site. I have been reading threads on here for years but never contributed till now. This is the second time I ran into this problem in the past six months. After disconnecting knob and tube wiring from a single pole single throw switch. I am reading 122 volts on (a Sperry 540 multimeter) between the hot wire entering the junction box and the load wire going to the light. these 2 wires are the only 2 wires in the JB. The old switch was working fine but the customer wants to update to a dimmer. When I touch the 2 wires together the fixture lights turn on with no problem. I installed the dimmer and it works fine but obviously no ground. I just don't feel right walking away from that weird voltage reading. I've seen phantom voltage readings before but never so high and never between the line and load of a switch. This happened to me about six months ago but that time I was using a Fluke 325 Multimeter and the 119 volts was at a 3way switch between one of the travelers and the point wire going to the light fixture. None of the fixtures involved had ballasts.......any thoughts...Thank You.
What do you feel is unusual here? An open point in any otherwise complete circuit will have full source voltage across it. Voltage reading to other grounded objects will depend on whether the conductor being measured is a grounded or ungrounded conductor of a grounded system.

As mentioned K&T systems often switched the neutral or "grounded" conductor. This can give you an illusion of things being "dead" when they are not.
 
I'm so sorry. Feeling a little stupid right now. I'm used to doing industrial electrical work...trouble shooting residential is not my thing. I forgot to mention a major detail last night. I do understand the concept of reading voltage through the load. The only reason I was testing the wires in the first place is because the customer removed the old switch and just left me the wires. Here is what confused me......The bulbs in the fixture are CFLs. Same as last time. I was unaware that you could read voltage through a lighting load if the load wasn't some sort of incandescent bulb. I might be wrong about that... like I said I'm not used to this kind of thing. I'm used to working with 500 kcmil, switchgear, cable tray, and 6" rigid conduit...ha ha.
 
Thanks everyone!! I appreciate your help.
George, I wish I could quit doing side work but unfortunately I've been laid off for 7 months and ran out of unemployment....and it's too late...my hair is already turning gray!!
:(
Thanks again.
 
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