Module, Low Voltage; Relay - Toro 315-8 User Manual

GLOSSARY

Module, Low Voltage

Purpose
The illumination of the battery light on the dash
indicates the battery voltage is too low. This is
controlled by the low voltage module (Figure 15).
How it works
The low voltage module is a voltage comparator,
checking the charge voltage from the engine regulator/
rectifier system. If the charge voltage is less than 11.3
volts D.C., the low voltage module senses this and
activates the indicator lamp on the dash which will light
until the voltage is over 12 volts D.C.
Figure 15
Testing
1. Before replacing the low voltage module, test the
battery to make sure it is fully charged and is in
good shape.
2. Next, check the charging system of the engine;
follow the procedure in the appropriate engine
service manual.
3. If the battery checks out and is in good condition
and the charging system checks out and is
charging properly and the battery light on the dash
is on, replace the low voltage module. Without
specialized test equipment, it is not practical to
test the low voltage module in the field.
3 - 14

Relay

Purpose
The relay is used in a variety of ways to turn circuits on
and off.
How It Works
A relay is an electrically actuated switch.
1. Coil: Terminals 85 and 86 are connected to a coil.
Applying 12 volts to these terminals energizes the
coil turning it into an electromagnet.
2. Switch: Terminals 30, 87, and 87a are actually
part of a single pole, double throw (SPDT) switch.
Terminal 30 is the common lead. The switch is
spring loaded so that 30 and 87a are connected
when the coil is not energized. When the coil is
energized, the switch is "thrown" and 30 and 87
are connected (Figure 16).
mvc-388
Testing
1. Disconnect the relay from the harness.
2. Verify the coil resistance between terminals 85
and 86 with a multimeter (ohms setting).
Resistance should be from 70 to 90 ohms. There
should be continuity between terminals 87a and
30 (Figure 17).
Figure 16
MVC-671
Demystification Glossary