A method for monitoring a the contact resistance (Rs) of the wiper of a sensor for a variable quantity, with a potentiometer (2), in which the position of the center tap (3) determines the value of the quantity, is improved in such a way that, first, when the sensor is used in an automatic control circuit, no control deviations occur and, second, the contact resistance of the wiper can be monitored with precision. This is achieved by the cyclic switching-on of a load (RLast), so that the contact resistance (Rs) of the wiper can be determined on the basis of the change in the voltage divider ratio.