With the wires from that jack disconnected entirely at the source end, and with no telephone instrument plugged in, use a meter and take a look at all the combinations of wires, one pair at a time.

Use the ohms scale and see if you have a dead cross or a resistance from the white/blue lead to all others. Then from the blue/white lead to all the others, etc, until you have looked at all the combinations.

If you see anything that is not a clear open (infinity), then disconnect the jack itself, and see if the meter reading goes to infinity.

You might have two leads shorted in the jack, or along the way where a staple has made a boo-boo. If you short a working lead with a spare, you actually add the capacitances of the two leads, and create an unbalance.


Arthur P. Bloom
"30 years of faithful service...15 years on hold"