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What's a Wiggy?

This is!

This is an excerpt from one of my advanced electrical courses for home and commercial building inspectors.  I have modified it slightly for this tutorial.   

George wells, BSEE, MBA, CMI, Licensed Master Electrician
©1992-2007

The venerable Wiggy^® is perhaps the most versatile electrical tester in the Electrician's, Home Inspector's, or electrical Technician's arsenal.   Almost any routine test you need to perform can be performed with a Wiggy.  The Wiggy can do the work of a multitude of other testers and it can usually do them better!

When using the Wiggy, you will quickly learn the feel of 120VAC, 240VAC, 480VAC, and DC Voltages.  AC Voltages will vibrate slightly and DC will have a distinctive SNAP of the plunger with no lingering vibration.  You will rarely need to look at the gauge once you learn the feel of each voltage.

You will need to look at the indicator under the bezel at the top of the Wiggy to determine the Polarity of a DC Voltage.  The Polarity indicator flips to Red or Black depending on the Polarity.  The Polarity indicator will tell you that the direction of flow is from Red To Black or from Black to Red.

Here are instructions for performing some common tests:

Receptacle Initial wiring check

BLACK in the SHORT slot RED in the LONG slot
 - should read 120V.  If it reads 0V, we already know that we have a problem.  It is probably a disconnected wire.  Plunger actuation should feel strong and solid
- If it reads 240V, the Grounded (a.k.a. Neutral) conductor has been lost and the receptacle is on a multi-wire circuit.  This is  a VERY DANGEROUS condition!  You will be able to feel the 240V in the plunger actuation.

Note: As an electrical contractor I never installed shared neutral circuits for this reason!  They are legal but when they fail - Watch out!

Receptacle Reverse Polarity check

BLACK in the SHORT slot and RED in the Grounding hole
 - should read 120V.  If not, the Polarity is Reversed.

BLACK in the LONG slot and RED in the Grounding hole
 - should read 0V.  If not, the Polarity is Reversed.

Receptacle Open Ground check

BLACK in the SHORT slot and RED in the Grounding hole
 - should read 120V.  If 0V, the GROUND is OPEN.

BLACK in the LONG slot and RED in the Grounding hole
 - should read 0V.  If not, the Polarity is Reversed.

GFCI Receptacle test

BLACK in the SHORT slot and in RED Grounding hole
 - should TRIP.   If it doesn't trip, there is a PROBLEM with the GFCI.

BLACK in the LONG slot and in RED Grounding hole
 - should read 0V and should NOT TRIP.  If it does TRIP, there is a PROBLEM with the GFCI.

Videos

Electrical Meters - An Introduction

Electrical Voltage, Current and Resistance

How To Use A Multimeter

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The Home Inspection Store