Arrangement for fault monitoring an electric consumer in a motor vehicle to detect short circuits and interruptions in the region of the consumer

An arrangement for fault monitoring an electric consumer in a motor vehicle, the electric consumer having a first phase of operation wherein the consumer is not driven and a second phase of operation wherein the consumer is driven, the arrangement comprising:

• first and second terminals connected to said consumer;
• two transmitting lines connected to corresponding ones of said terminals;
• first drive means for driving said consumer via said transmitting lines;
• second drive means for driving said consumer via said terminals;
• computer and storage means for generating a pulse-shaped control signal for said first drive means and said second drive means;
• voltage supply means for supplying a voltage to the consumer at said first and second terminals thereof whereby first and second potentials having potential values are present at said terminals, respectively, which shift when a fault is present and said voltage supply means including a pole defining a polarity thereof;
• detection means for detecting first and second potential values at said first and second terminals in both said non-driven phase and said drive phase thereof, respectively;
• means for supplying said detected potential values to said computer and storage means;
• said computer and storage means being adapted to form an upper limit value and a lower limit value when said consumer is in said driven phase and being further adapted to compare the detected potential values to said limit values to detect a possible fault;
• and,
• said computer and storage means also being adapted to detect a short circuit to said pole when said first potential value drops below said upper limit value and said second potential value exceeds said lower limit value and, said computer and storage means being further adapted to detect a short circuit or a shunt between said transmitting lines when said potential value at said first terminal drops below said upper limit value while at the same time, the potential value at said second terminal exceeds said lower limit value.