Fuel Pump Coupling

Plug-in coupling connecting the fan motor shaft to the fuel pump. Transfers rotary drive between the two units.

Application

The coupling transfers rotary motion from the motor driving the fan directly to the fuel pump, allowing both components to be driven by a single motor. The flexible connection compensates for minor misalignment between the motor shaft and the pump shaft.

Symptoms – when to replace

• No fuel flow or uneven fuel delivery despite a sound fan motor and sound fuel pump.
• Audible knocking or rattling at the connection between the motor and the pump during burner operation.
• The coupling is visibly cracked, chipped, or excessively worn when disassembled.
• The fan motor runs correctly but the fuel pump doesn't turn at all – may indicate a completely failed coupling.

How to choose the right part

Selection is based on reference number 448522 – the same part fits the therm CA and the therm-RP Starlet 3 in the version produced from October 2021. For older therm-RP units, it's worth verifying whether an earlier, different coupling variant is required instead.

When replacing the coupling, also assess the condition of the fan motor and fuel pump at the mounting point – uneven coupling wear may indicate misalignment between these two components.