CHECK A 12-VOLT SWITCHED BATTERY B(+) CIRCUIT FOR VOLTAGE
Theory of Operation
The purpose of the following procedure is to demonstrate how to
check the voltage of a 12-Volt switched battery B(+) circuit with
a test light or voltmeter.
NOTE:
The circuit shown
is an example, and is intended for demonstrational purpose only.
The following are circuit tests covered in this procedure:
Testing 12-Volt
Switched Battery B(+) Circuit Voltage With A Test Light
Testing 12-Volt
Switched Battery B(+) Circuit Voltage With A Voltmeter
NOTE:
Perform the
following test using a known good test light or functioning multimeter.
Below is a list of possible causes that could be related to a No
Voltage condition.
Possible Causes
OPEN CIRCUIT (CHAFED, PIERCED, PINCHED OR BROKEN WIRES)
OPEN FUSE
OPEN IN-LINE CONNECTOR
(BENT, PUSHED OUT OR CORRODED TERMINALS)
1.
TESTING 12-VOLT
SWITCHED BATTERY B(+) CIRCUIT VOLTAGE WITH A TEST LIGHT
NOTE:
Before testing any
circuits, first verify the 12-volt test light is operating properly.
Connect the 12-volt test light to battery ground or to any other known
good ground. Touch the lead of the test light to Battery(+). If the
test light is operational, it should illuminate brightly.
1.
Turn the ignition
off.
2.
Disconnect the
wire harness connector from the component that is being tested.
NOTE:
Check connectors -
Clean/repair as necessary.
3.
At this time, leave
all in-line connectors connected.
4.
Connect the 12-volt
test light to a known good ground.
5.
Use the test light
lead to carefully probe the Battery or Ignition voltage circuit in
the harness connector.
6.
First check with
the ignition off, next check with the ignition on, and lastly check
while cranking the engine.
Does
the test light illuminate brightly?
Yes
The circuit is not
open at this time or the condition that originally caused the open
may not be present at this time. Continue to monitor the test light
and wiggle the wire harness and connectors to check for an intermittent
open or excessive resistance condition.
Use the wiring diagram
as a guide to trace the circuits and look for any in-line connectors
where the open could occur intermittently.
Look for any chafed,
pierced, pinched, or partially broken wires.
Look for broken, bent,
pushed out or corroded terminals. Verify that there is good pin to
terminal contact in the related wire harness connectors.
Perform any Technical
Service Bulletins (TSBs) that may apply.
No
Repair the open in
the circuit. Use the wiring diagram as a guide to trace the circuit
and look for any in-line connectors where the open could occur.
One method to help
isolate the open is to disconnect any in-line connectors and measure
the resistance from one side of the in-line connector to the matching
component harness connector. If the open goes away, the open is on
the other side of the in-line connector.
If this is a fused
circuit, make sure to inspect the fuse. If the fuse is open, check
the circuit for a short to ground before installing a new fuse. The
circuit may have a short to ground causing the fuse to open. This
short to ground could be in the wire harness or in one of the components
the circuit is supplying voltage to.
2.
TESTING 12-VOLT
SWITCHED BATTERY B(+) CIRCUIT VOLTAGE WITH A VOLTMETER
NOTE:
The connector displayed
in the graphics are only an example.
1.
Turn the ignition
off.
2.
Disconnect the
wire harness connector from the component that is being tested.
NOTE:
Check connectors -
Clean/repair as necessary.
3.
At this time leave
all in-line connectors connected.
4.
Use a multimeter
set to measure DC voltage.
5.
Connect the ground
lead of the meter to a known good ground.
6.
Use the positive
lead of the multimeter and probe the circuit that is being checked
for voltage.
7.
Ignition on, engine
not running.
Is the
voltage within specifications for this circuit?
Yes
The circuit is functioning
properly or the condition that originally caused the open or short
may not be present at this time. Continue to measure the voltage and
wiggle the wire harness and connectors while checking for an intermittent
open or short.
Use the wiring diagram
as a guide to trace the circuits and look for any in-line connectors
where the short could occur intermittently.
Look for any chafed,
pierced, pinched, or partially broken wires.
Look for broken, bent,
pushed out or corroded terminals. Verify that there is good pin to
terminal contact in the related wire harness connectors.
Perform any Technical
Service Bulletins (TSBs) that may apply.
No
Repair the open or
short to ground in the circuit. Use the wiring diagram as a guide
to trace the circuits and look for any in-line connectors where the
short could occur.
One method to help
isolate the open or short is to disconnect any in-line connectors
that the circuit being checked runs through and check for the voltage
again. If the voltage is present, the open or short is on the other
side of the in-line connector.
