A vehicle heater includes a burner assembly unit (12) with a combustion chamber (18) to be fed with combustion air (V) and fuel (B) and a flame tube (24). A heat exchanger assembly unit (14) includes an inner heat exchanger housing (28) with an inner circumferential wall (30) and an outer heat exchanger housing (34) with an outer circumferential wall (36). A heat transfer medium flow space (40) is between the inner and outer heat exchanger housings, which are elongated in a longitudinal axis (L) direction. A waste gas backflow space (44), between the inner circumferential wall (30) and the flame tube, opens towards an exhaust gas outlet. A catalytic converter device (52) is provided in the waste gas backflow space associated with an energizable heating unit (58), or/and insulation material (64) is provided on an outer side (62) facing away from the heat transfer medium flow space.

A heater comprises a combustion chamber and a jacket extending about the combustion chamber. There is a fan having an output which communicates with the combustion chamber to provide combustion air. There is also a fuel delivery system having a variable delivery rate. A burner assembly is connected to the combustion chamber. The burner assembly has a burner mounted thereon adjacent the combustion chamber. The burner receives fuel from the fuel delivery system. There is an exhaust system extending from the combustion chamber. An oxygen sensor is positioned in the exhaust system to detect oxygen content of exhaust gases. There is a control system operatively coupled to the oxygen sensor and the fuel delivery system. The control system controls the delivery rate of the fuel delivery system according to the oxygen content of the exhaust gases.

A forced-draft pre-mix burner device has a housing that conveys air from an upstream cool air inlet to a downstream warm air outlet. A heat exchanger warms the air prior to discharge via the warm air outlet. A gas burner burns an air-gas mixture to thereby warm the heat exchanger. A fan mixes the air-gas mixture and forces the air-gas mixture into the gas burner. The fan has a plurality of blades having sinusoidal-modulated blade spacing.

A combustion chamber assembly unit for a fuel-operated vehicle heater includes a combustion chamber housing, a combustion chamber formed in the combustion chamber housing, an evaporator medium for the absorption of liquid fuel and for the discharge of fuel vapor into the combustion chamber, and a heating/ignition device for heating the evaporator medium or/and for igniting a mixture of fuel and combustion air formed in the combustion chamber. The heating/ignition device includes at least one radiation source for the emission of electromagnetic radiation into the combustion chamber and at least one absorption body for the absorption of electromagnetic radiation emitted into the combustion chamber.

A method to operate a fuel-operated vehicle heater comprising the lowering of a combustion air ratio λ between supplied combustion air and supplied fuel to a combustion chamber of the fuel-operated vehicle heater from a starting value λ.sub.start>1 to a range λ<λ.sub.start for a time period Δt.

A method is provided for operating a fuel-operated vehicle heater (10) during a start phase of combustion operation. The heater includes a combustion air feed device (26) feeding air and a fuel feed device (22) feeding fuel (B) to a burner area (12) with a combustion chamber (16). An electrically energizable ignition element (32) ignites a fuel/air mixture formed. The method includes energizing the ignition element (32) in a preheating phase prior to the fuel feed, at a time of entry into an ignition phase, detecting electrical resistance of the ignition element (32) and determining a desired resistance based on the electrical resistance of the ignition element (32) detected and operating the ignition element (32) in a resistance-regulating operating mode during the ignition phase such that an actual resistance of the ignition element (32) is in the range of the determined desired resistance of the ignition element (32).

A combustion air blower, especially side channel blower, for a fuel-operated vehicle heater, includes a blower housing (38). An air flow space (44), through which combustion air being fed can flow, is formed in the blower housing (38). Air flowing over an inlet area (55) into the air flow space (44) flows to a feed area enclosing a feed wheel (48). At least one hydrocarbon storage element (70, 88) is formed in the air flow space (44), for storing gaseous hydrocarbon present in the air flow space (44).

A combustion chamber assembly unit for a fuel-operated vehicle heater includes a combustion chamber housing (14) elongated in a direction of a housing longitudinal axis (L), with a combustion chamber (16) radially outwardly bounded by a circumferential wall (18), and with a combustion chamber bottom (20) axially delimiting the combustion chamber (16). A combustion air feed volume (36) is provided that is open to the combustion chamber (16) via a plurality of passage openings (38). A cooling medium feed device (46) is provided for feeding a liquid cooling medium to the combustion air feed volume (36).

A vehicle heater combustion chamber assembly includes a housing area (14) with an ignition element mount (36) supporting an ignition element (34) and another housing area (16) defining a fluid flow space (26) with an access opening (32). The ignition element or/and an electric ignition element line (76) is moveable through the access opening. An elastically deformable closing element (40) closes the access opening and includes a meshing area (48), interacting with a housing area wall (42) surrounding the ignition element access opening and including an inner meshing area supported relative to an inner surface of the wall, which faces the fluid flow space. The closing element includes a closing element bottom (44) with an outer bottom surface (94) oriented outwardly, in the direction away from the fluid flow space. The outer bottom surface is offset in a direction of a closing element longitudinal axis towards the fluid flow space.

A vehicle heater housing (46) has an inlet area (49), an outlet area (51) and an air flow space (47) for air to be heated with a burner chamber assembly unit (30), to be fed with combustion air and fuel. A heat exchanger area (11), including a heat exchanger housing (12), is elongated in the direction of a housing longitudinal axis (L) with an outer side (24) around which air flowing in the air flow space flows. Heat transfer ribs are on a side of the heat exchanger housing. The heater housing has a housing circumferential wall (56) and an outlet front wall area (58). The heat transfer ribs have a longitudinal edge (64) extending along the housing circumferential wall and a radial edge extending along the outlet front wall area. A distance of the radial edge from the outlet front wall area changes from radially outwards to radially inwards.