car wire fire the 12v source
12 Volt Housings

 
12 volt
car stereo
car security
 
 

 

 


12 Volts

Multimeter

A multimeter or a multitester, also known as a volt/ohm meter or VOM, is an electronic measuring instrument that combines several measurement functions in one unit. A typical multimeter may include features such as the ability to measure voltage, current and resistance. The use of a test meter is a VITAL identifying tool for accurate and safe installations.

 

Digital Multimeter

Digital instruments usually display digits, but may display a bar of a length proportional to the quantity measured.

digital-multimeter

 

Analog Multimeter

Analog instruments are usually based on a microammeter whose pointer moves over a scale calibration for all the different measurements that can be made;


analog-meter-12V

 

Testing/Polarity

In car audio and car security systems installations three polarities are most commonly tested, positive, negative, and reverse polarity.

Testing/Negative

Set meter to 12v DC. Connect the black probe to the wire in question. Connect the red probe to (+)12v constant. The meter should indicate "12" volts if the wire in question is ground and should show "0" if not.

Testing/Positive

Set meter to 12v DC. Connect the black probe to (-) ground. Connect the red probe to wire in question. The meter should indicate "12" volts if the wire in question is positive and should show "0" if not.

Testing/Accessory

Set meter to 12v DC. Connect the black probe to (-) ground. Connect the red probe to wire in question. The meter should indicate "12" volts if the wire in question is 12v positive with the key in the accessory and ignition positions only and should show "0" in the off and start position.

Testing/Ignition

Set meter to 12v DC. Connect the black probe to (-) ground. Connect the red probe to wire in question. The meter should indicate "12" volts if the wire in question is 12v positive with the key in acccessory and start positions and should show "0" in the off position.

Testing/Starter

Set meter to 12v DC. Connect the black probe to (-) ground. Connect the red probe to wire in question. The meter should indicate "12" volts if the wire in question is 12v positive with the key in the start position only and should show "0" in all other positions.

Testing/Reverse Polarity

Set meter to 12v DC. Connect the black probe to one lead to the motor. Connect the red probe to 12v constant. Operating the motor will indicate 12 volts in one direction or another.Reposition the black probe lead to (-) ground and the red probe lead the same wire off the motor. Operating the motor in the opposite dirction of the previous the meter should indicate (+)12v positive.

 

 

 

 

 

 

 

 

 

 

 


 

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