Patent ID: 7667164

Claim:
An auxiliary electric heater for a motor vehicle, comprising: a plurality of heat stages with at least one PTC heating element each, all of the PTC heating elements having the same, first rated heating power, and a plurality of radiator elements for dissipating the generated heat to a medium flowing through the radiator elements, wherein at least one of the heat stages contains a tolerance PTC heating element with a second rated heating power for correcting departures of the heating power of the at least one PTC heating element from the first rated heating power due to differences in manufacture, the second rated heating power being lower than the first rated heating power, wherein the PTC heating elements are arranged in levels in a layered structure of PTC heating elements and radiator elements, and wherein, in each of the levels, a pre-determined number of spaces for PTC heating elements is provided, and in one level for PTC heating elements with the first and the second rated heating powers not required, spaces are filled with dummy elements.