BoilerFaultCodesRavenheat E42 Fault Code
The Ravenheat E42 fault code means: your boiler has detected that heat is not moving through the system correctly, usually meaning the water is hotter in one part of the machine than another.. It appears on 9 Ravenheat models in our database.
Technical description: Different temperature error
What causes the Ravenheat E42 fault?
This fault occurs when the boiler detects a significant temperature difference between the flow and return pipes, meaning heat isn't leaving the unit fast enough. The most common reason is a lack of water circulation caused by a failing pump, a blockage in the internal pipework, or air trapped within the system.
This issue is more common in autumn when heating systems are first turned on after a long summer break, as pumps can seize during periods of inactivity.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Ravenheat models that show the E42 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ravenheat E42 fault code information on this page is sourced and cross-checked against the official Ravenheat service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026