| Fig. 1: Checking the resistance of a coolant temperature
sensor with an ohmmeter. Reading is 1.04 kilohms
|
| Fig. 2: Spark plug wires can be checked for excessive
resistance using an ohmmeter
|
WARNING
Never use an ohmmeter with power applied to the circuit. The ohmmeter is designed
to operate on its own power supply. The normal 12 volt automotive electrical
system current could damage the meter!
- Isolate the circuit from the vehicle's power source.
- Ensure that the ignition key is OFF when disconnecting
any components or the battery.
- Where necessary, also isolate at least one side of the circuit to be checked,
in order to avoid reading parallel resistances. Parallel circuit resistances
will always give a lower reading than the actual resistance of either of
the branches.
- Connect the meter leads to both sides of the circuit (wire or component)
and read the actual measured ohms on the meter scale. Make sure the selector
switch is set to the proper ohm scale for the circuit being tested, to avoid
misreading the ohmmeter test value.
