Posted 20 hours ago

HONEYWELL ST9400C Thermostat Programmer. 7, 2-Channel, 3 on/Off per Day, 24 V, White, 1

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Setting times for central heating and hot water to switch on and off can help reduce your home's energy consumption. Power Supply Examination: Without a detailed circuit diagram for the ST9400C, another expert suspected that the problem might lie in the power supply section of the device. The 48-volt supply, which typically involves a capacitor and diode, might be malfunctioning due to capacitor failures. Certain capacitors can lose their functionality when they remain un-polarised, leading to the deterioration of the dielectric surface. Replacing the capacitors may be a potential solution.

Can’t turn heating off | DIYnot Forums

The user sought advice on potential next steps, wondering if the issue lay with the programmer or another component in the system. Replacement: A straightforward solution proposed by several experts is simply to replace the malfunctioning programmer. Given the age of the device and the persistent issues, sometimes, it’s more efficient to replace rather than repair. Routine Maintenance: It’s essential to consider the health of the entire system. Even if the programmer is replaced or repaired, ensure that the boiler undergoes routine servicing as indicated in its manual. Neglecting regular maintenance can lead to a cascade of issues in the future.


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