Fault 50 Codes 121, 126, or 140 — Solar pump jammed or air in system

What does Fault 50 121-140 mean?

The Worcester Bosch Greenstar CDi Boiler displays Fault 50 with codes 121, 126, or 140, indicating that the solar pump is either physically jammed (sticking) or there is air present in the solar thermal system.

• Solar pump (SP) sticking due to a physical blockage
• Air trapped within the solar thermal system

Click steps to track your progress.

1. 1

   Turn off power to the solar system.

2. 2

   Locate the solar pump, unscrew the slotted screw on the pump head, and gently use a screwdriver to release the pump shaft. Do NOT strike the pump shaft.

3. 3

   Bleed the solar system to remove any trapped air and top up the heat transfer fluid if necessary.

4. 4

   Restart the system and check for the fault. If it persists, contact a qualified heating engineer.