Troubleshooting Ignition Switch/Starter Relay Circuit With Digital Multimeter, Delco 42Mt Starter - Volvo VN 2002 Service Manual

Group 33 Starting and Charging
Troubleshooting Ignition
Switch/Starter Relay Circuit With
Digital Multimeter, Delco 42MT
Starter
When the "start" position is selected at the ignition
switch, 12 volts are supplied to the starter relay coil. If
the starter relay coil is properly grounded, either directly
or through the overcrank protection switch, the starter re-
lay will energize and close the contacts between the
"common" and "normally open" terminals.
This creates a connection between the battery and the
starter solenoid feed. With this connection made, 12
volts are supplied to the starter solenoid, which en-
gages, and the starter motor begins to crank the engine.
The overcrank protection switch is designed to open and
prevent the starter from turning if the starter becomes
excessively hot. It should reset when the starter cools
sufficiently.
24
1 Check for 12.4V at the battery cable terminals to the
starter motor. If 12.4 V is not present or if a weak
battery(s) is suspected, see: "Battery Troubleshoot-
ing" page 15 for battery testing information.
2 Confirm that the cables between batteries are clean,
tight and in proper working order.
3 Remove the engine ECU fuses located in the bat-
tery box to prevent the engine from running during
the tests.
4 Unplug the starter relay from the connector.
Use digital multimeter J-39200 or equivalent tool to per-
form the test in the following table. The measuring points
referenced in the tables as C,D,E etc. correspond to
measuring points that are illustrated in the following
schematic.
For detailed, vehicle-specific schematics refer to the
"VN, VHD VERSION2 Electrical Schematics" in Function
Group 37.
Troubleshooting