There is disclosed a vehicle air conditioner which is capable of achieving protection of an air flow passage without hindrance, even when a temperature sensor which detects a temperature of an electric heater fails. When a detected value of an electric heater temperature sensor detecting the highest temperature among a plurality of electric heater temperature sensors 61 to 64 is in excess of a predetermined threshold value, a controller executes a protecting operation of limiting energization to the electric heater or stopping the energization. The controller calculates an estimated value Thtrest of the temperature which is calculated back from a consumed power of the electric heater, and when one of the electric heater temperature sensors fails, the controller executes the protecting operation on the basis of the highest value among the detected values of the temperature sensors other than the electric heater temperature sensor and the estimated value.

A heater device includes a heat generating body and a surface layer portion. The heat generating body includes a heating surface and radiates heat from the heating surface. The surface layer portion is stacked over the heating surface and is heated by the heat generating body. Furthermore, the surface layer portion changes color according to a temperature of the surface layer portion.

A heating apparatus for generating a hot air flow comprises a single fan, a burner heating element and a resistance heating element. In this respect, an air passage that conducts air to be heated and a combustion air passage that leads to a burner adjoin the fan downstream, wherein a combustion air flow in the combustion air passage can be controlled by a control element associated with the combustion air passage.

The on-state malfunction detection device detects an on-state malfunction, for instance, in an IGBT that is provided to correspond to a PTC element whose electrical resistance value varies according to temperature and that controls the electrification of the PTC element. In a state in which a turn-off instruction has been outputted from a control device to the IGBT, the on-state malfunction detection device determines through calculation an electric potential difference following voltage division of the voltage between the both ends of the PTC element, and detects an on-state malfunction of the IGBT when this electric potential difference is equal to or greater than a predetermined threshold value. This allows for the detection of an on-state malfunction in a switching element that performs an electrical conduction control for an element whose electrical resistance value varies according to temperature.

A device for determining a temperature of a resistance heating device, the device includes: a temperature sensor configured to detect the temperature of the resistance heating device; and an electronic data processing and/or control device configured to calculate a temperature change of the resistance heating device on a basis of a change in a resistance value of the resistance heating device and a relationship between the resistance value and the temperature of the resistance heating device, the electronic data processing and/or control device configured to validate the temperature of the resistance heating device detected by the temperature sensor, taking into account the calculated temperature change of the resistance heating device.