BoilerFaultCodesWorcester Bosch No CH function (DHW OK) Fault Code
Also written as NOCHFUNCTIONDHWOK — same fault.
The Worcester Bosch No CH function (DHW OK) fault code means: your boiler is providing hot water normally, but is not receiving the signal to turn on the central heating due to a control or wiring issue.. It appears on 1 Worcester Bosch model in our database.
Technical description: No link at ST2 Ls to Lr, or failed external control input to Lr. Failed programmer. Board fault.
What causes the Worcester Bosch No CH function (DHW OK) fault?
This issue occurs when the boiler is ready to provide heat but is waiting for a command from your thermostat or timer that never arrives. The most common reason is a faulty room thermostat or a broken internal programmer that can no longer send an electrical signal to 'call' for heat. Because the boiler is working fine for hot water, the problem is almost always located in the external controls or the wiring that connects them to the main circuit board.
This fault often comes to light during the first cold spell of autumn when homeowners try to turn their heating on for the first time after the summer break.
DIY fix possible
Ensure your wall thermostat is turned up higher than the current room temperature.Check that your heating programmer or timer is set to 'ON' or 'AUTO'.Replace the batteries in your wireless room thermostat if it has them.
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Gas Safe Register →Worcester Bosch models that show the No CH function (DHW OK) fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch No CH function (DHW OK) fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026