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voltage problem


On the front porch there is a light switch that has some sort of voltage problem.When you click the switch on the light doesn't come on unless you wiggle the switch,and then it doesn't always come on.Thinking it was the switch,I changed it out to a new one,still same thing.I then took the switch off and checked voltage at the wires.If I touch the wires with a meter it shows 87 vac ?? There are two wires going to the switch (old Rag Insulated wires,no color) I checked at the breaker controling this switch,it shows 120vac,back to the switch wires 85-87 VAC.What do you think is going on here,where am I losing voltage?

some where you have reverse polarity.
check the neutral and hot lead that leads to that switch.

Two wires going to the switch neither are colored coded (old rag wire) from one wire to the other 85-87 VAC.How do you tell netural or hot lead,and what should I be checking?Thank you so much for the reply.


Are you sure this is a single pole switch  -- i.e. the light switches on/off at only one location? If not, there is another 3way switch on the circuit that may be bad.

If you only have a 2 pole switch, one of the wires on the switch is a 'hot' -- i.e. have line voltage on it, and the other goes to the load (a light in this case). You need to check AC Voltage between the hot and a neutral line -- or a ground which should be at similar voltage to neutral.

Having low voltage at the switch may be due to too many other loads on the same circuit -- voltage drops as other things on the same circuit are using current. Try to turn off other loads before you test voltage.

The other thing I would try is a new bulb in the light fixture -- this may be flaky. I've had some really strange behavior out of bulbs before, and changing them did the trick.

If you're confused and still  suspect a problem, call in a pro.  Good luck.

Thank you so much,I'll try as per what you have said.


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