2026-04-07

Powerwall 3 Expansion Harness Replacement

Correction code 8248000858

Overview

Follow this procedure to remove a failed Powerwall 3 Expansion Harness and install a new one.

When performing this procedure in response to an isolation fault, replace ALL harnesses attached to the faulted Powerwall unit to resolve the issue. It is not possible to isolate which harness is faulted in this scenario.

Hazards

Figure 1. Shock

Safety and PPE

  • HRC2/CAT 2 arc-rated long-sleeved shirt (tucked in) and arc-rated pants or arc-rated coveralls
  • Fluke 1587 FC Insulation Multimeter or equivalent (rated for equipment voltage)
  • Proving unit (Fluke PRV240 or equivalent)
  • Lockout/tagout kit (locks, tags, hasps, lock box)
    • Simple LOTOV: One person. One individually controlled lock. One tag with name and contact information, and breaker clamp
    • Complex LOTOV: A complex LOTOV is required for multiple energy sources and multiple disconnecting means.
    • Individually controlled locks & tags
    • Breaker clamps
    • Lock box or tree hasp
      • The LOTOV Lead will be the person designated by the service visit assignment.
      • The LOTOV form linked here is required for Tesla complex LOTOV.
      • All individuals working on equipment are required to be included in the LOTOV.
  • Class 0 insulated electrical gloves with leather protectors or equivalent protectors (ANSI A4 cut-resistant, ANSI A3 abrasion-resistant, ASTM CAT2)
  • Leather 6 in. boots with EH rating and composite toe or safety-rated shoes with leather upper
  • Safety glasses (ANSI Z87.1 or EN 166)

General Equipment

  • N/A

Required Parts and Tools

  • Replacement Powerwall 3 Expansion Harness(es)
    Informational PurposesAn informational icon, calling your attention
    Note
    Use the same length Expansion Harness as the harness being replaced:
    Table 1. Expansion Harness Options
    Expansion Harness Part Number Expansion Harness Length
    Tesla P/N 1875157-05-y 0.5 m (20 in)
    Tesla P/N 1875157-20-y 2 m (6.5 ft)
    Tesla P/N 1875157-40-y 4 m (13 ft)
  • Torx T40 driver

Procedure

  1. Before performing any repairs, ensure the replacement Expansion Harness does not exhibit isolation issues by running a continuity test between each terminal and the attachment bolt:
    1. Set the multimeter to continuity mode, then test the function by touching the probe tips together. An audible beep and a low value on the multimeter screen indicate the multimeter is functioning correctly.
    2. Place one multimeter probe on the Expansion Harness positive terminal. Ensure the probe is touching the metal contact within the plastic housing.
    3. Place the other probe on the screw in the middle of the Expansion Harness. Confirm the multimeter does not beep, and the screen reads OL or a very high resistance reading (> 10 MOhms).
      If the multimeter does beep, a new Expansion Harness is required.
    4. Repeat this step to test continuity between the negative (-) terminal and the center screw.
  2. Update the Tesla One app on your mobile device to version 26.2 or later. See Install / Update Tesla One for instructions to update the app.
  3. Update the Powerwall 3 software version to 26.2 or later. See Update Powerwall 3 Software for instructions to update Powerwall 3 software.

    For Expansion Harnesses exhibiting isolation issues, Powerwall 3 allows a set number of pairing retries. Once the number of retries has been exceeded, Powerwall 3 disables pairing attempts and an alert will be present in Tesla One. The minimum software versions listed above are required to clear the Tesla One alert once the Expansion Harness has been replaced.

  4. Repeat step 1 to confirm continuity on the other connector on the Expansion Harness.
  5. Put on arc flash PPE.
  6. Perform Powerwall 3 Lockout/Tagout.
  7. Remove arc flash PPE.
  8. If present, remove any straps securing the Expansion Harness to the wall. These straps and their locations will be reused, so set them aside for later.
  9. Use a T40 driver to remove the screw from the Expansion Harness currently plugged into the Expansion / Powerwall 3, then pull outward to disconnect the harness from the unit. Repeat to remove the other end of the harness from the Expansion / Powerwall 3.
  10. Visually inspect the Expansion port, as well as the replacement Expansion Harness. Ensure no debris is present in the port or in the harness connectors.
  11. Plug the replacement Expansion Harness into the Expansion port, pressing the connector into the port to seat it. Tighten the screw with a T40 driver to 11 Nm (100 in-lb).
  12. Route the Expansion Harness in the same manner the original harness was routed. Ensure the harness is not twisted. If there were previously straps securing the harness, ensure the harness can be routed through the straps. See the Powerwall 3 Installation Manual for additional guidance on routing Expansion Harnesses.
  13. Plug the other end of the Expansion Harness into the Powerwall 3 / Expansion, pressing the connector into the port to seat it. Tighten the screw with a T40 driver to 11 Nm (100 in-lb).
  14. Ensure both ends of the Expansion Harness are fully seated in their respective ports. No gasket should be visible on either connector.
  15. If applicable, replace the straps to secure the Expansion Harness to the wall.
  16. Repeat the process for any additional harnesses that must be replaced.
  17. Take a photo of the QR code label on the Tesla Asset Controller (TACO) before replacing the Powerwall 3 front cover. The login credentials on this label are required to connect to Powerwall 3.
  18. Clean up the work area and put on arc flash PPE.
  19. Energize Powerwall 3 System. When turning the Powerwall 3 switch on during the energization process:
    1. Turn the Leader Powerwall 3 switch on (this is the unit the Expansion units are connected to).
    2. Within 5 seconds, the logo LED on the front of Powerwall 3 will blink red; while the LED is blinking:
      1. Turn the Powerwall 3 switch off.
      2. Turn the switch back on.

      This sequence resets all electronic control units (ECUs), which allows the Leader Powerwall 3 to reset. After resetting, Powerwall 3 will detect the Expansion unit(s).

  20. Remove arc flash PPE.
  21. In the Tesla One app, connect to the Leader Powerwall 3 and select Start System.
  22. Select System, then select the Powerwall 3 the harness was originally connected to.
  23. If present, select the Clear Alert button to clear the alert for an Expansion Harness fault. Without clearing this alert, Powerwall 3 may not retry pairing with the Expansion unit, which can lead to an additional service visit being required. If no alert is present, confirm both Tesla One and Powerwall 3 have been updated to version 26.2 or later, then wait 5 minutes to see if the alert appears.
  24. Select the Back arrow to return to the Devices tab, then confirm the Expansion unit(s) appear in the device list (indicating they successfully paired).