CHECK THE RESISTANCE OF A CIRCUIT USING AN OHMMETER
Theory of Operation
The purpose of the following procedure is to demonstrate how to
check the resistance of a circuit with an ohmmeter.
NOTE:
The circuit shown
is an example, and is intended for demonstrational purpose only.
The following are circuit tests covered in this procedure:
Testing For An
Open Circuit Using An Ohmmeter
NOTE:
Perform the
following test using a known good multimeter.
Below is a list of possible causes that could be related to an
Open Circuit condition.
Possible Causes
OPEN CIRCUIT (CHAFED, PIERCED, PINCHED OR BROKEN WIRES)
OPEN IN-LINE CONNECTOR
(BENT, PUSHED OUT OR CORRODED TERMINALS)
TESTING FOR
AN OPEN CIRCUIT USING AN OHMMETER
NOTE:
Before measuring the
resistance of any circuit, first measure the resistance between the
two leads of the multimeter. Take this value and subtract it from
the value recorded when measuring the resistance of the circuit being
checked (The meter leads can add 0.5 ohm or more of total resistance).
1.
Turn the ignition
off.
2.
Disconnect the
wire harness connectors of the components that contain the circuit
suspected of being open.
NOTE:
Check connectors -
Clean/repair as necessary.
3.
At this time leave
all in-line connectors connected.
4.
With the component
wire harness connectors disconnected, use a multimeter set to Ohms
(Ω), and measure the resistance of the circuit.
5.
Use one lead of
the meter and probe the circuit in one harness connector.
6.
Use the other lead
of the meter and probe the same circuit in the other harness connector.
Is the
resistance in the circuit below 10k ohms?
Yes
The circuit does not
contain any excessive resistance or the condition that originally
caused the excessive resistance may not be present at this time. Continue
to measure the resistance of the circuit, wiggle the wire harness
and connectors to check for an intermittent open or poor connection.
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 excessive
resistance in the circuit between the two wire harness connectors.
Using the wiring diagram as a guide, trace the circuit and check for
any in-line connectors where the open or excessive resistance 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 or excessive resistance is
not present, the open or excessive resistance is on the other side
of the in-line connector.
