The procedure will describe what you need to do, but you can learn more about
what a multimeter is and how to use one in the Science Buddies resource How to Use a Multimeter.
Not exact matches
Some vehicles have refrigerant pressure sensors which you can backprobe with a
multimeter to see
what the pressure is together with a lookup table.
Standard digital
multimeters can measure current and help you identify
what in your vehicle is consuming your battery's juice.
Here's
what you'll need to build your own MightyMintyBoost: Tools: Soldering iron Scissors Wire cutters Pliers (or muiltitool)
Multimeter Metal shears Clear packing tape Materials: MintyBoost kit Lithium polymer battery charger (the original one specified was discontinued) For better performance use the Adafruit Solar Lithium charger (connections are similar but it's slightly larger - see update below) 3.7 v 2000mAh Lithium Polymer battery JST connector / wire Small solar cell 2» x 3» adhesive backed Velcro Small double sided adhesive squares Altoids tin 7/10/10 UPDATE: Adafruit now also sells all the parts you need to make this a bit more mighty.
While for serious stuff a Fluke is worth more than a billion cheap Chinese
multimeters, having 3 or 4 of the latter will be immensely more useful than a single top brand one because seeing in real time the battery voltage and
what develops around a voltage divider when you change the resistors ratio has no price.
Same for instrumentation: an oscilloscope is worth the information you get by using it, so you have first to know
what it does measure, otherwise it's not even worth a 5 bucks Chinese
multimeter.