Easy step by step guide on how to use a voltmeter, this information pertains
to all car related applications.
Difficulty Level - 2
A voltmeter is usually used in many ways in the automotive repair field, its
most basic function is to check for voltage at a particular component such as a
battery, brake light or switch.
- To check for voltage (12 volts) at a particular accessory switch
the meter to the DC voltage setting.
Step 2 - Grasp both negative and positive leads and hold them against
the desired test point such as a terminal or wire, the meter will instantly give
Voltmeter Set to DC Voltage
Step 3 - Start the engine and watch the meter rise in voltage as the alternator
starts producing voltage. Switching the voltmeter to AC voltage will test the alternator
diodes for leakage which will destroy a battery over time, voltage should be 0 in
Voltmeter Test Leads
Step 4 - Switching the meter over to ohms will test the internal winding
circuit of any electronically controlled device such as a relay, sensor, fuel injector
Voltmeter Alternator Test
Step 5 - If high resistance or an open circuit is present the unit
has failed. Switch the meter to mV to test milli volt generation from a sensor,
such as a crank angle sensor while the engine is cranking over.
Set Meter to Ohms
Step 6 - A voltmeter works great for testing pulse voltage which is needed
for fuel injectors and ignition coils.
Test Fuel Injector
Step 7 - Gently install a paper clip into the connector to aid in testing
when needed. If a sharp probe is used to pierce the wire for testing, use electrical
tape to reseal the area. (Note: Do not damage terminals.)
Testing Ignition Coil Pulse
A digital voltmeter is ideal for home and shop use for troubleshooting
and locating faulty wiring. A digital voltmeter can be used to check for good continuity of an
electrical circuit by using the ohms of resistance feature. To check for power at
a particular electrical circuit, locate a good clean ground before testing begins.
Digital Voltmeter Function Range
Installing Paper Clip
- DC Voltage 200mV to 1000V
- AC Voltage 200mV to 750V
- DC Current 200A to 10A
- Ohms200 to 2M
- Diode Check
- Transistor Check
Article first published 2016-02-05