Your solar heating pump has stopped moving because something is physically blocking it from spinning internally.
This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.
Technical description: Solar pump (SP) sticking due to physical blockage.
What causes this fault?
This fault occurs when the pump responsible for moving heated fluid from your solar panels to your cylinder becomes physically jammed. The most common reason is a buildup of debris within the solar fluid or the fluid itself degrading over time, which creates a sticky residue that prevents the internal parts from spinning. If the pump cannot rotate, the system cannot transfer solar energy to your hot water.
This issue is often more noticeable during the spring and summer months when high solar gain puts the pump under constant demand after periods of winter inactivity.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
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A boiler cover plan would cover faults like Fault 50 121 — no call-out fees, no surprises.
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