How to Test a Powerpoint Safely with a Plug-In Tester
I went out to a rental in Norwood last spring to replace a melted oven isolator and ended up doing a quick lap of the house with my Megger and a plug-in tester. Twenty-three powerpoints. Six faults. Two reverse-polarity GPOs in the kitchen — the same kitchen where the tenant had been running her toddler’s sterilising kettle for two years. One open earth in the bathroom. One open earth in the second bedroom. And a textbook active-to-earth reverse in the garage that would have killed anyone touching a metal lawnmower while standing on damp concrete. The tenants had been living there four years. The landlord didn’t know. None of it was their fault — someone had been DIY-ing behind face plates two owners ago. I get this question alot at parties: “Is there a way to check the wiring in my house without paying a sparky?” Yes. There is. For $25. And every renter, every new-home buyer, every parent should own one.
What you’ll need
- An AS/NZS-rated plug-in socket tester with 230V Aussie three-pin plug (Jaycar MS6860D at $24.95, Arlec PT250 at Bunnings around $19, or Fluke ST120 at a wholesaler for $50)
- A torch for powerpoints hidden behind furniture
- A pen and notepad to record results room-by-room
- A roll of red electrical tape and a Sharpie for marking faulty outlets
- About five minutes per room — quicker once you find a rhythm
Step 1: Buy the RIGHT tester — Aussie-spec only
This matters. Most cheap testers on Amazon and Temu are 110V American models. They either won’t work on Aussie 230V or they’ll fry on insertion, sometimes with a satisfying flash. Stick to AS/NZS-marked models with a moulded Australian three-pin plug — active right, neutral left, earth bottom when looking at the front. Jaycar’s MS6860D is reliable; the Fluke ST120 is the pro-grade option. Don’t bother with the “GFCI test” button on US-spec testers — Aussie RCDs sit at the switchboard, not the GPO, and the button does nothing useful here.
Step 2: Calibrate on a known-good powerpoint
Before you trust any reading, plug into a powerpoint you’ve been using daily — the kitchen bench, the one running your toaster. If the lights show “correct wiring” (usually two yellow plus one red, but read YOUR tester’s legend — brands differ), you’re good. If the calibration outlet shows a fault, either that GPO is wired wrong or your tester is faulty. Try a second known-good outlet to confirm before you walk the rest of the house thinking everything’s broken.
Step 3: Walk every room systematically
Start at one end of the house and work your way through. Bedrooms, lounge, hallway, kitchen, laundry, garage, sheds. Every powerpoint, every gang on a double. If a switched outlet is off, flick it on first — the tester needs power to read. Note results on the pad: “Lounge GPO behind couch — correct” or “Bedroom 2 — open earth”. Don’t skip the awkward ones behind the wardrobe; those are often the ones where someone did dodgy work and hid it.
Step 4: Read the patterns honestly
Common results and what they mean:
- Correct wiring: active, neutral, earth all present and in the right pins. Move on.
- Open earth: no earth wire, or earth disconnected. Common in pre-1980 homes never upgraded. Appliances with metal cases (kettle, washing machine) have no earth fault path. Get a sparky.
- Open neutral / open active: dead point. Won’t even run a lamp. Definately needs a sparky.
- Reverse polarity (active/neutral swapped): appliance still runs, but switching the appliance off interrupts neutral instead of active — internals stay live. Kills people who open “off” appliances.
- Active/earth reverse: rare but lethal. The earth wire is now live. Touching the metal case of any earthed appliance completes the circuit through your body. Don’t use that point, ring a sparky immediately.
Step 5: Pay special attention to outdoor and shed GPOs
Outdoor GPOs and shed circuits are the most likely to be dodgy — they’re usually retrofits done by previous owners in the 1990s when “her brother who does electrical” was a common phrase. Pop the weatherproof flap, plug in, read. If your shed was wired by anyone other than a licensed contractor, expect at least one fault. Garden GPOs in particular often have buried Cordtech with slug-eaten insulation feeding them.
Step 6: Test every wet-area GPO and confirm RCD coverage
Bathroom shaver outlets, laundry GPOs near the trough, kitchen splashback points — all of these should show correct wiring AND should be on an RCD-protected circuit. Test the RCD coverage by tripping the relevant RCD at the switchboard and checking the wet-area GPO is dead. AS/NZS 3000 has required RCDs on these circuits since 1991, but plenty of older bathrooms have never been touched. See also how to reset a tripped safety switch for understanding RCD behaviour.
Step 7: Test USB-A and USB-C ports separately
Modern Aussie GPOs often have integrated USB charging ports — Clipsal Iconic, HPM Excel, Legrand Excel Life all do versions. The plug-in tester only checks the 240V pins, not the USB output. To check USB output, plug a USB voltmeter (Klein USB-A/C tester, $25) and verify a clean 5V is coming out. Faulty USB modules don’t trip RCDs because they’re isolated low-voltage, but they will cook your phone battery over time.
Step 8: Document the results and stick the sheet in the switchboard
Write the date, tester model, and a list of any faults on a single sheet. Stick it inside the switchboard cupboard with a thumbtack or magnet. When you sell the house, that document is gold for the building inspection. When the next tenant moves in, you hand it over. AS/NZS 3760 calls this a “test record” and its the kind of thing a real contractor would do anyway.
Step 9: Mark faulty outlets so no one uses them
Stick a strip of red electrical tape over any faulty GPO with “DO NOT USE — FAULT” written in marker. Tell everyone in the house. A reverse-polarity outlet is most dangerous when nobody knows; once it’s marked off, the danger is contained until the sparky arrives. A typical fix for a single point is $90–$140 in Adelaide. If you’ve found three or four faults in one circuit, ask the sparky to quote the lot together — they’ll discount the labour.
Step 10: Re-test after ANY electrical work
Whether the work was a sparky fitting a new oven, a renovation, or a full rewire, plug your tester into every affected GPO AFTER the sparky leaves. They should do this themselves and give you a CoES, but a 10-second double-check has caught at least three jobs in my career — including one of mine — where someone refit a face plate with the wires on the wrong terminals. Trust but verify.
When to call a tradie
Plug-in testing is yours. Everything else — diagnosing the cause, removing the cover plate, reterminating active/neutral/earth, replacing a faulty GPO, anything inside the switchboard — is licensed-only work in every Australian state under AS/NZS 3000 and the state Electrical Safety Acts. Don’t try to “just swap the two wires back” if you find a reverse polarity. The moment you remove the cover plate, you’ve performed illegal electrical work that voids your house insurance. The sparky charges $90–$140 to do it legally with paperwork; cheaper than a fire claim being denied.
Common screw-ups
- Buying a US-spec tester from an overseas seller — it’ll either not work or explode on insertion.
- Skipping the calibration step and assuming a “fault” reading is real when actually the tester is the problem.
- Testing only the visible outlets and missing the ones behind furniture — those are often the dodgy ones.
- Trying to fix a fault yourself by removing the face plate — instantly illegal, voids insurance.
- Forgetting to test both sides of a double GPO independently — they have separate actives and only one side may be faulty.
Cost & time
$25 for the tester, free for the labour. About an hour for an average 3-bedroom Aussie home. Repair costs: $90–$140 per faulty point if separate, or bulk discount if multiple faults on one circuit. Full circuit replacement (cabling + GPOs on one section) is $1,500–$3,000. Full house rewire on pre-1970 stock is $8,000–$25,000+ but adds significant value and 50 years of safe wiring.
You can’t legally rewire a powerpoint in Australia, but you absolutely can test one — and the test is what matters. The number of “she’ll be right” wiring jobs hidden behind innocent-looking face plates in Aussie rentals would shock you. A $25 plug-in tester is the only legal, reliable way for a non-sparky to know what’s actually behind a GPO. Here’s the safe play: buy one this weekend, walk the house in an hour, document what you find, mark the duds, and hand the sparky a one-visit fix-list. Lend the tester to the kids when they move into their first share house. Best electrical investment you’ll ever make.
