Car blower controlling resistor protection - includes short-circuiting conductor contacted by overheating resistor

摘要

The protection of metal resistor controlling the speed of blower in the air conditioner of passenger space of cars eliminates overheating of the resistor which presents a hazard of fire for the dashboard. The protection is based on a short-circuiting conductor of the resistor (2) by a bar or a cylinder (5) separated from the resistor by air or a thin plastic layer. This avoids the unreliable safety switching since the resistor (2) tends to overheat and, therefore thermally dilate near the infeed terminal (6). If the resistor (2) is in the form of a wire spiral then the first turn of the latter expands more than the other turns and melts away the insulation to contact the short circuiting cylinder (5). As a result, the resistor would not carry a current and cool off to operate in normal conditions. Fast blower speed can be selected by operating switch (13) to connect cylinder (5) to the source (3).