Worcester Bosch Wiring Harness Mk3 No On/Off Button 87186841510

This is a Mk3 wiring harness supplied by Worcester Bosch for its Greenstar i System boiler range. It carries the internal low-voltage connections between the control components, so the appliance's electronics and switches communicate correctly. The Mk3 variant is specified for units built after the FD986 production point, where the on/off button is not present on the fascia.

• The boiler fails to respond to the fascia controls or the on/off function is inoperative
• Intermittent faults or lockouts that clear when the wiring loom is disturbed
• Visible damage to the harness: chafed insulation, scorched or brittle connectors, or a broken plug latch
• Error codes relating to control or communication faults that persist after other components are checked
• Loose or corroded pins at the harness plugs, causing unstable readings during a service

• Check the appliance GC number and serial number against the compatibility list to confirm the correct harness variant
• Confirm the boiler was built after FD986, as the Mk3 harness is the version without an on/off button
• Note the alternative part number 1022706 when cross-referencing older documentation
• This part is fitted to a gas appliance; installation must be carried out by a Gas Safe registered engineer.