Fuel Fired Heater
A small burner running on the vehicle's own fuel, fitted to warm coolant and cabin on engines too efficient to do it themselves — a modern diesel converts so little fuel into waste heat that on a cold day it may never heat the cabin properly. Its fault codes frequently record correct behaviour rather than a defect: the module declines to run it when fuel is low, at high altitude, or when battery voltage is marginal. Where it genuinely underperforms, soot is the usual reason, and it accumulates from short bursts rather than long runs — every start and stop passes through a cool, rich phase that leaves deposits, so the vehicles that need the heater most are the ones that clog it.
Also known as: auxiliary heater, webasto, eberspacher, fuel burning heater, ffh, parking heater, coolant heater
Referenced by 5 codes
Codes involving this component (5)
Other components in Cooling
- Electric Coolant Pump 149
- Engine Coolant Temperature Sensor 105
- Engine Coolant Flow Control Valve 82
- Radiator 61
- Active Grille Shutter Module 53
- Engine Coolant Bypass Valve 42
- Thermostat 40
- Cooling Fan 40
- Engine Coolant Level Sensor 15
- Water Pump 12
- Radiator Coolant Temperature Sensor 11
- Coolant Expansion Tank 8
- Coolant Degassing Valve 3
- Oil Cooler 1
Information, not instruction
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