Alternator Controller         Back to Projects

The Balmar MC-612 is a fully automatic alternator regulator that has served VALHALLA well for many years.  There are times, however, when I find it desirable to either turn the alternator off or reduce the output power, in this case to reduce wear on bearings and belts when powering for extended periods and do not need a quick initial charge.  Typically, when weighing anchor with the windlass, its one horsepower motor will draw the batteries down considerably and this puts a large load on the engine while maneuvering to get underway.  This is an ideal time to reduce the charging load.

The regulator uses a field wire (brown) to energize the alternator when connected to battery voltage.  A switch in this wire controls when the alternator is operating.

The alternator temperature sensor (an optional item) switches the regulator into the 'small engine' mode when heating causes the temperature sensor to short out and reduces alternator output by approximately 50%.  Manually shorting this input simulates the overheated condition regardless of whether a sensor is connected or not.

This is the schematic of the project.

This project involved wiring two switches, two LEDs and two resistors into a small plastic box.


  I used small switches which required a 6 mm hole for the switch and a 2 mm hole for the retaining washer.


The LEDs require a 5 mm hole for a snug fit.













Before installing wiring the box was assembled and drilled for wiring entry.












The underside of the box is shown here.  Not yet connected are the field wires which go to the switch in the upper left hand corner and which come through the upper access hole.













With completion of the wiring I tested the switches using a direct connection to the temperature sensor terminals.

This was to ensure that there was no interference from the sensor.











Satisfied that things were working properly I completed the wiring with connectors to permit double connection to the temperature sensor terminals.


Now to find a label maker . . .!