EV Charger Troubleshooting Wizard — Diagnose Your Fault
EV Charger Troubleshooting Wizard & Complete Diagnostic Guide
Interactive troubleshooting wizard
Answer a few questions about exactly what your charger is doing, and we'll walk you through the same diagnostic process an installer would use.
Quick reference — don't want to click through?
If you already have a good idea what's happening, here are the most common symptoms and their likely fix at a glance.
Stage 1 — Gather information
Before touching anything, pin down exactly what's happening. This single step is what separates a 30-second fix from an hour of guessing — most of the diagnosis below depends on these details being accurate.
Pick the category that matches: no lights at all, lights on but won't start, starts then trips or stops, or a clicking/buzzing noise. These lead to genuinely different causes.
New car, new cable, a power cut, or a change to your home wifi/router. Note anything, even if it seems unrelated.
If it trips, roughly how long after starting? If it won't start, does the light change colour at all when you plug in, even briefly? If there's a message on the app, what does it actually say?
Stage 2 — Basic troubleshooting
These checks are safe for anyone to carry out — no tools, no opening anything up, just observation and using the switches as they're designed to be used.
Look at the switch for your charger circuit — does it sit in a different position to the others (often somewhere in the middle rather than fully up)?
Turn it fully off, then fully back on with a firm motion. It should click into place and hold.
Most RCBOs have a small test button, usually yellow, marked "T". Press it — it should trip the device instantly.
If there's a separate isolator near the charger, confirm the handle points straight down (the normal "on" position).
Look for the cable sticking out very slightly (1-2mm) rather than sitting flush. If so, power cycle the charger and push it firmly in again right after.
On a tethered cable, look at the top two pins in the vehicle-end connector for blue/green residue. Turn the charger off first, then clean gently with a soft toothbrush if found.
Check the vehicle's own settings, not just the charger's app, for any charging schedule or smart tariff (like Octopus Intelligent) that could be restricting when it charges.
If schedules aren't the cause, temporarily disable load balancing in the app and retry. Still nothing? Try a different cable if you can. Still nothing? Try a different vehicle if you can.
Stage 3 — Advanced diagnosis (interpreting patterns)
These checks don't need tools either, but they involve reading a pattern rather than a single yes/no answer — this is where you start narrowing down why, not just what.
| Pattern observed | What it likely means |
|---|---|
| Trips within about a minute of starting | Genuine earth fault, faulty cable, or a faulty RCBO — test the RCBO on its own (unplugged) to check which |
| Trips after roughly 20-40 minutes | Heat build-up — likely a 32A RCBO working close to its rated capacity during sustained charging |
| Speed fluctuates before it stops/pauses | Dynamic load balancing responding to household usage — normal, not a fault |
| Steady, then stops cleanly ("charging complete") | Vehicle's own daily charge limit reached, or a scheduled window ending |
| Mentions a "PEN fault" — happens once | Charger correctly protecting against a brief voltage spike on the supply — power cycle to clear |
| Mentions a "PEN fault" — happens repeatedly / same time of day | Points to a genuine local supply issue, not just a spike — worth an electrician investigating |
| Repeated clean click, ~once a second | Contactor repeatedly trying to engage — almost always load balancing |
| Repeated grinding/straining noise | Motor-lock mechanism struggling to engage, possibly obstructed |
Stage 4 — When you need a qualified electrician
These signs mean the fault is inside the electrical installation or the charger's internals — not something to open up or work around yourself.
Stage 5 — When to contact the manufacturer, installer, or DNO
Some issues aren't really "broken" in the electrical sense — they need a different kind of follow-up.
Frequently Asked Questions
How can I tell if my RCBO has failed rather than just tripped normally?
A healthy RCBO resets with a firm, positive click and holds in place. If it feels loose or spongy, or springs back to the tripped position shortly after you reset it, that indicates the device itself has failed and needs replacing by an electrician.
How long after starting a charge should it trip before I suspect a specific cause?
A trip within about a minute of starting usually points to a genuine earth fault, a faulty RCBO, or a cable fault. A trip after 20 to 40 minutes typically points to heat build-up, often meaning a 32A RCBO is operating close to its rated capacity during a sustained session, which may indicate a 40A upgrade is worth assessing, subject to the cable and circuit also supporting it.
What does it mean if my charger mentions a PEN fault?
A PEN fault means the charger has detected the supply voltage falling outside regulated limits and has stopped charging as a protective measure. A one-off occurrence is usually a brief supply spike, cleared by power cycling the isolator. If it happens repeatedly or at a consistent time of day, it suggests a local supply issue worth having an electrician investigate, potentially involving the Distribution Network Operator (DNO).
How do I work out whether a charging fault is caused by the cable, the car, or the charger?
Strip the situation back to basics: disable any charging schedules and smart tariffs on the vehicle, disable load balancing if possible, then try charging. If that resolves it, the cause was scheduling. If not, try a different cable, then a different vehicle if possible. Whichever swap resolves the fault identifies the faulty component; if nothing resolves it, the charger itself likely needs professional inspection.
Is it safe to press the RCBO's yellow test button myself?
Yes — this is a normal, designed-for-use function of the device, not something that requires an electrician. It should trip the device instantly. If it doesn't trip after a couple of attempts, that's a sign the RCBO has failed and needs replacing.
What's the difference between basic troubleshooting and something that needs an electrician?
Basic troubleshooting covers anything you can check by observing or using switches and buttons as they're designed to be used — resetting a breaker, pressing a test button, checking a cable is seated properly. Anything that involves opening an enclosure, working on internal wiring, or replacing a protection device crosses into work that must be carried out by a qualified, registered electrician.
Prefer the full written guides?
Why won't my EV charge? · Why does my charger keep tripping? · Why is my EV charging slowly?
This guide provides general troubleshooting information based on common installer practice. Any work involving your consumer unit, wiring, or a charger's internal components must be carried out by a qualified, registered electrician. EcoHarmony is a retailer of EV charging and electrical protection equipment, not a repair or technical support provider — for issues this guide doesn't resolve, please contact your charger's manufacturer or a qualified electrician directly.
