DIY Repair of a Telephone Line

Written by jack brooks
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DIY Repair of a Telephone Line
Keep your telephone working. (telephone image by Goran Bogicevic from

Save money and time by troubleshooting your telephone wiring and get your phone line working again. Use your basic electrical skills to locate and repair the problem and avoid the hassle of scheduling an appointment with the phone company and a long wait for the service technician to show up.

Skill level:

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Things you need

  • Phillips and flat blade screwdrivers
  • Digital multimeter
  • Small jump lead with alligator clips
  • Needle-nose pliers
  • Wire cutters
  • Small butane lighter
  • Standard interior telephone wire
  • Vinyl electrical tape
  • 3/8-inch-diameter heat-shrink tubing

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    Examine Interior Connections

  1. 1

    Unplug the phone or other device, such as a fax machine or DSL modem, from the telephone line. Examine any visible telephone cable for breaks or punctures. If visibly damaged wiring is found, follow the procedure in Section 2. Remove the cover or cover plate on the baseboard or wall socket enclosure. Examine the wires coming into the enclosure to be sure they're connected correctly. The red incoming telephone cable conductor should be attached to the terminal for the red wire feeding the socket. The green wire should be attached similarly to the matching colour.

  2. 2

    Check any additional connections at the socket, for example, a two-line phone system. These telephone cable conductors are usually black and yellow for a second line. They should attach to the other socket terminals, matching colours as in Step 1.

  3. 3

    Open any additional interior wall or baseboard sockets and check their connections as noted above. Leave the covers off the enclosures for further testing.

    Repair Damaged Interior Wiring

  1. 1

    Note any breaks or punctures needing repair in the visible telephone wiring and remove enough of the staples or clips securing it to give access for repair. Cut off the torn or punctured portion of the exposed telephone cable. Cut a sufficient length of replacement telephone cable to replace the cut portion.

  2. 2

    Cut two 3-inch pieces of heat-shrink tubing and slide them onto the cut telephone cable. Strip 1 inch of the outer insulation off each end of the existing telephone cable. Strip 1 inch of the outer insulation off each end of the length of repair telephone cable.

  3. 3

    Strip 1/2 inch of insulation off each conductor on the respective cable ends. Use the needle-nose pliers to twist together the bare conductors of each matching coloured wire on the cut and replacement telephone cables. Cover each spliced connection with electrician's tape.

  4. 4

    Slide the pieces of heat-shrink tubing over each joined end of the repaired telephone cable after all the conductors are spliced and taped. Heat the heat-shrink tubing with the butane lighter sufficiently to shrink it tightly onto the wires, being careful not to overheat and melt it. Secure the repaired telephone wiring with staples or clips.

    Test Wiring

  1. 1

    Open the outside telephone interface (demarcation) box by unscrewing the customer access screw on the cover. Locate the red and green wires coming from the interior house wiring and unscrew them from their terminals.

  2. 2

    Clamp one alligator clip on the end of the small jump lead to the red wire in the exterior demarcation box. Clamp the other alligator clip of the jump lead to the green wire to temporarily connect the red and green conductors.

  3. 3

    Locate the interior wall or baseboard socket enclosure closest to the exterior demarcation box. Set the digital multimeter to "Ohms" and measure the resistance between the red and green conductors of the telephone cable in this interior socket box. It should read no more than 10 or 15 Ohms. A high or infinite reading on the digital multimeter indicates a defect in the cable between the outside demarcation box and the interior socket enclosure.

  4. 4

    Replace the defective telephone cable and determine alternative routing along exterior walls or under the house structure, if the existing defective cable is in the walls. Obtain the services of a licensed electrician if it's necessary to pull replacement telephone cable through the walls.

Tips and warnings

  • Plug a standard wired telephone into the telephone jack in the exterior demarcation box to test the phone line from the pole.
  • Use a wireless telephone extender to add an extension phone without running additional telephone cable.

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