Somerset Regal L4-151 2.5L (1985)
Speedometer Module: Description and Operation
Voltage is applied to the speed sensor buffer from the gauges fuse, with the ignition switch in RUN, BULB TEST, or START. Sensor input voltage is
applied to the buffer from a generator mounted in the transaxle. The number of pulses per second from the buffer varies with the speed of rotation of the
shaft.