Testing a power point with a basic plug-in socket tester is one of the few electrical checks a NZ homeowner can safely carry out themselves. The tester does all the work — you simply plug it in and read the indicator lights. It won't tell you everything about a circuit, but it can quickly flag common wiring faults that need a licensed electrician's attention.
What Is a Plug-In Socket Tester?
A plug-in socket tester (sometimes called a mains tester or outlet tester) is a small device with a standard three-pin plug on one end and a row of indicator lights on the other. When plugged into a power point, it checks the basic wiring configuration and shows a light pattern that corresponds to a fault code printed on the device or its packaging.
These testers are widely available at Bunnings and Mitre 10 for a modest cost — as a rough guide, expect to pay somewhere in the range of $20–$50. Make sure you buy one designed for the New Zealand/Australian 230 V, 50 Hz standard with a three-flat-pin plug (AS/NZS 3112 format).
Safety First
Before you start, keep these points in mind:
- Never open the power point or touch any wiring. That is restricted electrical work under the Electricity Act 1992 and must only be done by a registered electrician or other authorised person.
- Make sure your hands are dry and you are standing on a dry surface.
- If you see scorch marks, smell burning, or the outlet is physically damaged, do not plug anything into it — call a licensed electrician immediately.
- Keep children away from the area while you are testing.
For general electrical safety guidance, refer to WorkSafe NZ.
Step-by-Step: Using the Tester
Step 1 — Read the fault code chart first
Every socket tester comes with a small chart showing what each combination of indicator lights means. Familiarise yourself with it before you start so you can read results quickly.
Step 2 — Plug the tester in firmly
Insert the tester into the power point with a firm, straight push until it seats fully. A loose connection can give a misleading reading.
Step 3 — Read the indicator lights
The lights will illuminate within a second or two. Common results include:
| Light Pattern | Typical Meaning |
|---|---|
| All correct lights on | Socket is correctly wired ✓ |
| No lights at all | No power — check the circuit breaker |
| "Earth fault" indicated | Earth wire missing or not connected |
| "Live/Neutral reversed" | Active and neutral wires swapped |
| "Live earth reversed" | Dangerous — active and earth swapped |
Step 4 — Test every power point you are concerned about
Work through each outlet methodically. Note which ones show faults so you can report them accurately to your electrician.
Step 5 — Check the RCD (safety switch) if your tester has that function
Some plug-in testers include an RCD test button. Pressing it should trip your RCD (residual current device / safety switch) within milliseconds. If it does not trip, your RCD may be faulty — this is a serious safety issue and requires a licensed electrician. Note that this function only works on circuits protected by an RCD.
What the Results Mean for You
- Correct wiring result: The outlet is functioning as expected. This does not guarantee the circuit is fault-free, but it is a good sign.
- No power: Check your switchboard for a tripped breaker or blown fuse. Reset the breaker once. If it trips again immediately, stop and call an electrician.
- Any wiring fault indicated: Stop using that outlet and arrange for a registered electrician to investigate. Reversed or missing earth connections are genuine safety hazards.
Limitations of a Plug-In Tester
A basic socket tester is a useful first step, but it has real limitations:
- It cannot detect high resistance connections (loose terminals that can cause overheating).
- It cannot test the condition of the wiring behind the wall.
- It cannot verify the full RCD response time or loop impedance — tests that a licensed electrician performs with professional equipment.
- It will not detect a fault if both active and neutral are swapped together in a way that still allows current to flow.
For a thorough check — especially in older NZ homes with wiring that may pre-date modern standards — a full electrical warrant of fitness or inspection by a registered electrician is the only reliable option.
When to Call a Professional
Always contact a registered electrician (registered with the Electrical Workers Registration Board) if:
- Your tester shows any wiring fault.
- An RCD fails to trip during testing.
- Breakers trip repeatedly.
- You notice flickering lights, warm outlets, or a burning smell.
- Your home is older and has not had a recent electrical inspection.
- You are a landlord — under the Healthy Homes Standards, rental properties must have working RCDs and smoke alarms, and electrical systems must be safe.
All wiring work, replacing outlets, and any work inside a switchboard is restricted electrical work in New Zealand and is illegal for unlicensed people to carry out. You can find qualified local electricians on tradedirectory.co.nz.
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