Your boiler's solar heating sensor has detected an issue, likely meaning your solar panels aren't assisting with your hot water production as they should.
This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.
Technical description: Collector temperature sensor (T1) fitted on collector array inlet.
What causes this fault?
This fault occurs when the boiler loses communication with the sensor located on your solar thermal panels. The most common reason is that the sensor itself has failed due to extreme outdoor temperatures or the wiring connecting the panels to your boiler has become damaged or loose.
This fault is more frequently detected during peak summer months when high collector temperatures can stress an aging sensor or cause it to fail.
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.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like Fault 53 125 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.