Electrical Testers

Basic test equipment used in today’s shops may include an analog type meter, a VAT (Volt-Amp-Tester), DMM (Digital Multimeter), logic probe

Solid state circuitry & components are very sensitive to excess voltage & amperage flow. This includes static electricity. Make sure you remove the static charge before touching solid state circuitry or components. Metal will remove charge, but not other materials. Touching metal body parts removes static charge

 Jumper wire size should be equal to or larger than circuit under test with inline fuse or circuit breaker installed  Never use jumper wires to bypass a load in circuit

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 Use jumper wire only for “temporary’ bypassing  Never use self-powered test light to check circuit with power applied  Never use Ohmmeter with power applied to circuit ◦ May damage meter

  Circuit breakers can be used in place of fuses to temporally test short circuits   High current amp probe are used to test current draw on motors and solenoids   Low current amp probes can be used to test current ramping of relays and solenoids

 Testing of circuits that include solid state devices requires a high impedance multimeter (10 mega ohms or greater)  Never use test lights on solid state circuits

 Recommended “not” to touch printed circuit boards  Static electricity from yourself or soldering iron may destroy solid state components

 Connections must be clean and have good contact “critical” for circuit operation  Disconnect battery during welding with arc welder  Do not disconnect any coil or solenoid with power applied unless “instructed” to do so

 When testing circuits on air bag equipped vehicles - follow OEM instructions  Most air bag systems have back-up power supply

 Proper jump starting procedures must be followed ◦ Ignition must be “OFF” when disconnecting or connecting cables ◦ All accessories should be turned “OFF” ◦ Cable polarity must be correct + to + and - to - ◦ OEM may recommend battery replacement vs jump starting  Remove battery or disconnect cables when using battery charger

This test equipment is used to test for voltage presence, voltage level, voltage drops, current, resistance and temperature. Special adapters may be required to perform some of these tests

 Other tests if meter is equipped ◦ Frequency - measured in MHz ◦ RPM ◦ Duty cycle measured in % ◦ Pulse width (PW) measured in ms

 Voltage testing ◦ Connect leads parallel to circuit being tested ◦ “OL”, “OFL” or “1” indicates overload

 Voltage drop testing ◦ Connect leads parallel to portion of circuit being tested

 Current testing ◦ Connect leads in series to circuit being tested or use amprobe CAUTION: DO NOT OVERLOAD METER DAMAGE MAY OCCUR 20 amp max

 Resistance testing ◦ Remove power from circuit ◦ Isolate component from circuit ◦ Connect meter in series with component ◦ “OL”, “OFL”, or “1”indicates overload

 Temperature testing ◦ Use proper adapters for meter ◦ Probe must match temperature and substance being tested

 Frequency testing ◦ Attach leads parallel to circuit under test  RPM test ◦ Place clamp-on probe around number one spark plug wire ◦ Select two or four cycle engine

 Duty cycle and pulse width (PW) testing ◦ Attach leads parallel to component under test ◦ Compare readings to OEM specs ◦ Test parasitic current draw by disconnecting battery ground and putting meter in series with cable and battery post/ testing amps

The logic probe is an electronic test light( is used to replace test light for digital testing). It provides real time measurement. The logic probe has a high internal resistance (approximately 100K ohms resistance) so it will not load the circuit

 General procedures ◦ Connect power leads to battery CAUTION: DO NOT CONNECT TO VOLTAGES THAT EXCEED MANUFACTURERS SPECIFICATIONS. IT WILL DESTROY LOGIC PROBE

 LED’s indicate voltage range and voltage change ◦ Red ◦ Red = high voltage 10V to 16V ◦ Green ◦ Green = low voltage 0V to 4V ◦ Yellow ◦ Yellow = pulse voltage changes trigger LED