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How to Use a Multi Meter For Car Alarm Installation

Using your Digital Multi Meter for Car Alarm or Remote Start Installation

There are two ways to test wires in your automobile, you can either use a digital multi meter, or a test light. I recommend using a Digital Multi Meter (DMM) to test all wires before connecting anything to them. Although using a “test light” may seem easier, it is not safe, and honestly it’s not any easier. Test lights have been known to damage vital computer components, as they add resistance and pull power from the wire you are testing. Another reason you may want to use a DMM is because it is much more accurate, and gives you much more information. “Seeing” what a wire is actually doing is much better than a light turning on or off. To test a wire, simply poke the wire with the lead of your multi meter. The leads are pointy, and give you the ability to pierce the insulation of the wire just enough to make contact with the inner winding, without damaging or stripping the wire back. If you find difficulty in this, or to avoid accidentally slipping and poking your finger, companies sell EZ hook probes. They will plug directly into your meter, and allow you to safely test wires using a spring loaded pin.

Above: EZ hook test probes use a spring loaded button on the bottom of the probe to safely and easily puncture through the insulation of wires. Right: Standard test probe leads
In vehicle electronics, you are looking for voltages between 0 and 14.4 volts. (usually around 12.5) For this reason, you will want to set your DMM to a range of >20DVC. This means that the meter is looking for voltages under 20 volts. The image below will give a visual understanding on what I mean.

Above is a general picture of a Digital Multi Meter. These devices are capable of testing an assortment of electronic circuits. For our alarm/remote start/ or keyless install, we will only be using a few features. The V~ is AC voltage, and is NOT used in our application. We want to set our meter to “VDC” or “V—“. The numbers on the dial are listing the range. Because we are testing for voltages less than 20 volts, we will set the meter to VDC or V-20.
To test for a “positive trigger” wire,
A positive trigger wire will have no voltage when not active. When activated, the wire will power to +12 volts.
1. Secure the black lead of your DMM to a good ground(bare metal).
2. Probe the wire you wish to test with the red lead of your DMM.
3. Note if the switch or trigger directly affects the voltage your meter reads.
To test for a “negative trigger” wire,
A negative trigger wire has +12 volts or no voltage when inactive. When activated, the wire will represent a ground (-).
1. Secure the red lead of your DMM to a +12 volt source.
2. Probe the wire you wish to test with the black lead of your DMM.
3. Note if the switch or trigger directly affects the voltage your meter reads.

Check Out Vehicle Wiring Diagrams

Check Out the Car Alarm Installation Guide

Check Out the Remote Start Installation Guide

Article Source: http://www.articleslash.net

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