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How to Test Your Campervan's Electrical System (British Standards)

Updated: Apr 13

Wiring up a campervan isn’t finished until it’s tested. Whether you’ve installed a full 230V hookup system or a 12V battery setup, testing ensures your van is safe, compliant, and reliable. In this guide, you’ll get step-by-step instructions to perform essential tests for both AC and DC systems, aligned with UK standards: BS 7671 Section 721 for 230V systems and BS EN 1648-2 for 12V DC. This guide is written specifically for DIY van builders — clear, practical, and to the point.


Testing isn’t just about passing an inspection. It’s about ensuring that your electrics function properly and safely over the long haul — from campsite to remote forest trail.

This guide will ensure that your van passes its electrical inspection first time round, and that you get your EIC (Electrical Installation Certificate).

How to Test Your Campervan's Electrical System (British Standards)

 

Shane, the founder of The Van Conversion, is a campervan professional dedicated to helping people transform ordinary vans into homes on wheels. He has authored Roaming Home, and teaches The Van Conversion Course, guiding many people through their van builds. Shane also writes The Van Conversion Newsletter, where he shares practical tips and insights. After completing two van builds and living on the road full-time since 2020, he is passionate about sharing his expertise with others.


This post contains affiliate links, which means that if you click a product link and buy anything from the merchant (Amazon, eBay, etc.) we will receive a commission fee. The price you pay remains the same, affiliate link or not. By using these links, you are helping me to continue writing free educational content! To understand our policies on content, affiliate commissions, and liability, please review our Terms of Use.


Did you know you can get a free electrical wiring diagram by signing up for The Van Conversion Newsletter?

 

Index


Testers You'll Want

Having the right tools makes a huge difference when testing.


Here's your must-have list:

  • Multimeter – For continuity, voltage, and resistance (a DIY staple)

multimeter
Fluke 117 is an excellent multimeter
  • Socket Tester – Fast polarity and wiring check for 230V outlets

Socket Tester
Kewtech KEWCHECK103 socket tester
  • Clamp Meter (AC & DC capable) – Detect current draw on your DC system and diagnose phantom loads

Fluke 325 Clamp Multimeter AC-DC
Fluke 325 Clamp Multimeter AC-DC
  • Battery tester (lead-acid & lithium capable) - For testing battery health

Topdon TB6000Pro
Topdon TB6000Pro is one of the few battery testers that also work with lithium
  • Multifunction Tester (MFT) – For testing cable insulation, loop impedance, RCDs

    • or, purchase individually: Insulation Resistance Tester, RCD Tester

fluke multifunction tester
Fluke 1662 multifunction tester

If you don’t have a multifunction tester (MFT), you can often rent one for a day or two from a tool hire shop. At minimum, you should have a decent multimeter and a socket tester.


Pro Tip: Always test your tools before use. Confirm your multimeter reads ~230V on a known mains socket, and test continuity across a known conductor. A broken test lead or flat battery in your tester is worse than no tester at all — it gives false confidence.


Want to understand the electrical regulations behind the testing?

Before diving into how to test your campervan’s electrical system, it’s helpful to understand why these tests matter — and how different standards apply depending on where you live or travel.


We’ve written an in-depth guide comparing the three major campervan electrical standards:

  • BS 7671 (UK wiring regulations)

  • EN 1648-2 (European DC system spec for leisure vehicles)

  • NEC (the US National Electrical Code)


Whether you're installing solar, shore power, or a full off-grid system, understanding the differences and overlaps between these standards will help you build a safe, reliable, and legal electrical system.



AC System Testing (230V)

Before we hop into the AC testing techniques, a quick note: if your van has both shore power and an inverter, you'll need to test each system separately to ensure they’re both safe and correctly configured. In other words, you need to test both systems.


Testing Both Shore Power and Inverter Inputs

If your van has both a shore power hookup and a 230V inverter, you should repeat the AC testing procedures, described in this article for each input source.


Do the full sequence once while powered by shore hookup and again while powered by your inverter. This ensures both systems are correctly wired and properly protected.


Note: For the Ze (external earth loop impedance) value, you only measure this on shore power. Inverters don’t have a true external supply earth, so Ze is not relevant in that case.


Neutral-earth bonding in inverters

Many RCDs rely on the inverter correctly simulating an earth reference — some inverters do this with built-in neutral–earth bonding relays, while others do not. That’s why it’s critical to verify RCDs still trip correctly under inverter power, especially if your RCD is located upstream of the inverter output.


Some high-quality inverters (like the Victron Multiplus) include a built-in relay that bonds neutral to earth automatically when running. Others — especially cheaper or standalone inverters — do not bond neutral to earth, which means your RCD won’t work unless you install a separate bonding relay (which closes the circuit between Neutral and Earth when the inverter is ON).


Quick test: With the inverter powering the system (no hookup connected), use a multimeter to measure resistance between Neutral and Earth at a socket.

~0Ω? You have a bond — good.

Open loop (OL) or high resistance? No bond — your RCD won’t function properly under inverter power.


Key rule: You should have one N–E bond active at a time —

  • One for shore power (at the hookup supply),

  • One for inverter power (via the inverter or bonding relay).


Never both at once.


Always perform your RCD tests under inverter power as well as shore power to confirm your protection works as expected.


With that behind us, let's jump into the five key AC system safety tests outlined by BS 7671 Section 721:


1. Continuity Testing


Note: This is a dead test — power must be completely turned off and all appliances disconnected. You're checking for low resistance across all cables (earth, live, and neutral), ensuring they're intact, connected, and not compromised along the way.


Why it matters:

Continuity testing is essential because it verifies the integrity of every conductor. Not just the earth. If any cable is damaged, loose, or poorly crimped, you may get flickering lights, intermittent faults, or worse — heat buildup and potential fires.


For example, during my own testing, an earth bolt had rusted so badly that it created a huge resistance until the connection stopped working entirely. That’s not just a nuisance — that’s a critical safety hazard and could cause a fire.


What you’re testing:

  • Protective Earth (PE) – Ensures fault current can flow freely back to the RCD/MCB

  • Line (Live) – Confirms circuit connectivity from distribution board to the device

  • Neutral – Completes the return path; needs continuity for proper operation


Continuity testing with a multimeter

Steps:

  1. Turn off all power and disconnect devices.

  2. On your multimeter or MFT, select continuity mode.

  3. For earth continuity:

    • Attach one probe to the van’s chassis or your main earth bonding point.

    • Use the other to test:

      • Each outlet’s earth pin

      • Any metal appliance cases

      • Metal pipework or bonded surfaces

    • Acceptable reading: <0.5Ω

  4. For line and neutral continuity:

    • Clip one lead at the MCB/RCBO output or fuseboard terminal.

    • Clip the other at the device end (switch, socket, appliance connection).

    • Acceptable result: typically a very low resistance (e.g., 0.1–0.3Ω for short van runs)

    • Use wire identification or tone probes if unsure which conductor is which.


Using a multimeter: Insert the black probe into the COM port and the red probe into the VΩ port. The multimeter will beep if it detects continuity (a complete path). If the circuit is open—such as when a switch is OFF—there will be no beep.

fluke multimeter
Fluke 117 True RMS Multimeter

According to the EIC certificate, you only need to test (The "first socket" is the one furthest from the consumer unit):

  • First socket earthing & chassis

  • First socket & gas pipe


However, that's bare bones. It is good practice to continuity test all your cables to ensure there is no resistance. Especially in a campervan where:

  • Wires are often run behind walls, around corners, and through insulation

  • Crimps, wagos, and screw terminals are common

  • Vibration from driving can loosen connections over time


Common problems this catches:

  • Crushed cables during wall cladding or cabinetry installation

  • Loose crimps or terminal screws not torqued properly

  • Breaks in ring final circuits (if used — though not allowed under BS 7671 Section 721)

  • Wrong gauge wire — long runs in thin cable might look fine but test with higher resistance


Troubleshooting Continuity Failures

If continuity is failing at a particular point, use the steps below to identify and fix the issue:

  • No reading on one outlet’s earth:

    • Check that the outlet’s earth wire is correctly terminated — it might be loose, popped out, or clamped on insulation instead of copper.

    • Verify that the cable between this outlet and the previous one isn’t damaged or disconnected.

    • To rule out cable failure, disconnect both ends and test the earth conductor alone for continuity end-to-end.

  • High resistance (e.g., 1–2Ω):

    • Could indicate a loose terminal or corrosion on an earth bond or screw.

    • Check all screw terminals are properly tightened.

    • Inspect the main earth bolt to the chassis — it should be on bare, clean metal (not painted or rusted).

    • Clean the surface and apply a corrosion inhibitor grease after tightening to ensure a long-term low-resistance connection.

  • Polarity issues (unexpected continuity between live and neutral):

    • If you detect continuity between the live output of your distribution board and a neutral terminal (with all switches off), this may indicate a wiring error.

    • Possible causes include cross-connections, stray copper strands, or mislabelling.

    • Cross-check your wiring against your diagram and visually inspect the terminals for unintentional bridges.


Bonus tip:

Continuity testing is also how you locate “mystery faults.” If your light turns on and off intermittently, or a device fails to power, trace the cable with a continuity test end to end — you'd be surprised how often it's a dodgy crimp or hidden splice.


Note: Before testing the continuity with a MFT, you should "Null" the tester, as your testing probes will have some resistance in them already and we want to cancel this out - much like we would zero a kitchen weighing scales.


2. Insulation Resistance Test

Note: This is a dead test — power must be completely turned off and all appliances disconnected. This test Detects faults in cable insulation that might cause leakage current, short circuits, or fires.


Safety: During this test 500V of power will flow through your system Take adequete precautions. Do not touch anything and wear rubber gloves.


What to look for:

  • Pinched wires

  • Screw-damaged insulation

  • Moisture or condensation between conductors

Insulation resistance (IR) test with a multifunction tester

Steps:

  • Disconnect all sensitive electronics: chargers, inverters, control panels

  • Ensure that your RCD is in the OFF position

  • Use an MFT set to 500V DC insulation test mode

  • Test between:

    • Live to Earth (L-E)

    • Neutral to Earth (N-E)

    • Live to Neutral (L-N)

  • Each result should be >1 MΩ, though many new installs measure in the hundreds of MΩ


Important: Turn the RCD to the OFF position before performing insulation resistance tests. This prevents the 500V DC test voltage from travelling upstream toward the shore inlet or connected AC chargers. While turning the RCD off does not fully isolate it internally, it limits the test path to only the fixed wiring on the load side of your system. For best results, keep all wall and appliance switches ON, disconnect any sensitive electronics, and test between Live–Earth, Neutral–Earth, and Live–Neutral.

fluke multifuction tester
Fluke Multifunction tester

Tips:

  • Do these tests with all switches ON so that the tester probes the full circuit

  • If your system includes surge protection devices or neon indicators, they can skew readings. Isolate them where needed


Troubleshooting Continuity Failures

If your continuity tests return strange or unexpected readings, here’s how to diagnose the problem:


  • No reading at an outlet’s earth (open circuit):

    • Check that the earth wire is properly terminated at the outlet.

    • Ensure it’s not clamped on insulation instead of copper.

    • Confirm the cable between the previous and current outlet is intact.

    • To test the cable alone: disconnect both ends and measure resistance between its conductors. Infinite resistance? You’ve got a break.

  • High resistance (e.g., 1–2Ω):

    • Look for partially loose terminal screws.

    • Check the main chassis bond — is it on clean bare metal?

    • A corroded or painted surface can cause a poor connection.

    • Clean the bond, tighten securely, and consider using corrosion inhibitor grease for long-term protection.

  • Unexpected continuity (e.g., between live and neutral):

    • With all switches off, there should be no continuity between live and neutral.

    • If you find some, double-check your wiring: a stray strand or misconnection could be bridging them.

    • Also check that no appliance was accidentally left connected during the test.



3. Socket Polarity Test

Note: This is a "Live test", ie. the system is turned ON.


Why it matters: Ensures Live, Neutral, and Earth are not crossed. A reversed polarity could leave metal casings live when the device is off.


Socket Tester

Steps:

  • Power on the system

  • Plug a socket tester into each outlet in turn

  • Check the lights. The tester will display a "correct" pattern or warn of:

    • Live/Neutral reversal

    • Missing Earth

    • No Neutral


Bonus test with a multimeter:

  • Live to Neutral: should read 230V

  • Live to Earth: should read 230V

  • Neutral to Earth: should read near 0V


Any deviation indicates wiring error. Miswiring isn’t always obvious — devices often still work with Live/Neutral reversed, but it leaves appliances and people vulnerable during faults.


Here is a handy table of fault combinations with socket testers:

Plug Pins

Status

LED1

LED2

LED3

Buzzer

N E L

Correct

GREEN

GREEN

OFF

ON

N E L

Correct

GREEN

GREEN

OFF

ON

E N L

E/N Swap

GREEN

GREEN

OFF

ON

X E L

Missing N

OFF

GREEN

OFF

PULSE

X L E

Missing N

OFF

GREEN

OFF

PULSE

X N L

Missing N

OFF

GREEN

OFF

PULSE

X L N

Missing N

OFF

GREEN

OFF

PULSE

N X L

Missing Earth

GREEN

OFF

OFF

PULSE

L X N

Missing Earth

GREEN

OFF

OFF

PULSE

E X L

Missing Earth

GREEN

OFF

OFF

PULSE

E L X

Missing Earth

GREEN

OFF

OFF

PULSE

L E X

L Fault

GREEN

GREEN

RED

PULSE

N L X

L Fault

GREEN

GREEN

RED

PULSE

L N X

L Fault

GREEN

GREEN

RED

PULSE

N L E

LE reverse

OFF

GREEN

RED

PULSE

E L N

LE reverse

OFF

GREEN

RED

PULSE

L E N

LE reverse

GREEN

OFF

RED

PULSE

L N E

LE reverse

GREEN

OFF

RED

PULSE


RCD test using socket tester: If your tester has a button labeled “T” or “RCD Test”, you can press it. It should trip the van’s RCD just like our RCD test earlier. This is a convenient way to test the RCD regularly (for example, it’s good practice to press the RCD’s built-in button every few months – you can also use the socket tester button if it’s easier to reach a socket). In our thorough test above, we already exercised the RCD, so this is optional now.


4. Earth Loop Impedance Test (Zs and Ze)

Note: This is a "Live test", ie. the system is turned ON.


Why it matters: This test confirms that your circuit can carry fault current back to earth quickly enough to trip a breaker or RCD. If Zs is too high, the protection might not activate.


Before we hop into the Z tests, I want to quickly cover the formula:

Zs = Ze + R1 + R2 (R1 = Live conductor resistance, R2 = Earth conductor resistance)


Ze is the measured earth fault loop impedance at the origin of the installation, typically taken between the incoming live (line) conductor and the main earth terminal, and represents the impedance of the external supply (DNO side) including the service cable and earth path. Or in simple terms: this is the earth loop impedance of the campsite you are on, or workshop you are building in. We only need this, because it helps us calculate our Zs, which is the earth loop impedance INCLUDING our van.


Steps for Zs (at the farthest socket):

  • Power ON

  • Set your MFT to "Loop" or "Zs" (use the no-trip setting if protected by an RCD)

  • Set your MFT to the correct trip time: 0.4s (per BS7671 regulations)

  • Set the multimeter settings to match your MCB (eg. Type C, 10A)

  • Plug into a socket (or use test leads at the terminal)

  • Run the test and record the impedance

Earth loop impedance test

Targets:

  • For a 32A MCB (Type B): Zs < 1.73Ω

  • For a 16A MCB (Type B): Zs < 2.73Ω


Steps for Ze (at the van’s inlet):

  • Isolate all downstream circuits

  • Measure between Live and Earth at the hookup inlet

  • Expect ~0.3–0.8Ω for a TN supply


Troubleshooting High Loop Impedance


If your Zs reading is too high, check:


  • Poor earth connection

    • Check screw terminals in your hookup plug and socket

    • Make sure the earth pin has solid contact

    • Inspect the chassis earth bond — it should be tight and on bare metal (not over paint)

  • Long or thin extension cable

    • Avoid lightweight or excessively long cables

    • Use a proper 2.5mm² hookup lead, ideally no more than 25 metres

    • Longer cables increase resistance and Zs

  • Site supply issue

    • Garage or garden outlets may have high Ze

    • Small generators often have high internal impedance

    • Measure loop impedance at the source outlet to confirm

    • If the supply is the issue, note it and rely on RCD protection

  • Chassis as bonding point

    • The earth wire in the hookup cable is the main protective conductor

    • Chassis should be bonded, but it's a backup reference — not the primary return path

    • Earth rods are sometimes used off-grid but aren’t necessary on-grid

    • If testing via inverter with no earth reference, loop tests may show open circuit


5. RCD Trip Test (and Ramp Test)

Note: This is a "Live test", ie. the system is turned ON. This is our second set of RCD checks after the Z checks.


Why it matters: Your RCD must trip quickly if there’s a fault. These tests check trip speed and leakage sensitivity.


Steps:

  • Power ON

  • Set your MFT to 30mA RCD test mode

  • Perform each test at both 0° and 180° (your tester should switch this automatically or give you a manual option)

  • Results:

    • ½ × test: Should NOT trip

    • 1 × test: Trip within 300ms

    • 5 × test: Trip within 40ms

  • You should then turn your MFT to "Ramp" and perform a ramp test. RCD should trip at a current between 15mA and 30mA. This test should be carried out at both 0° and 180° phase angle


If it fails: Replace the RCD immediately. RCDs degrade over time, especially in mobile environments where vibration is common.

Test

Current

Angle

1

½ times 30mA (15mA)

2

½ times 30mA (15mA)

180°

3

1 times 30mA (30mA)

4

1 times 30mA (30mA)

180°

5

5 times 30mA (150mA)

6

5 times 30mA (150mA)

180°

Troubleshooting RCD Issues


  • RCD doesn’t trip at 1× or 5× test:

    • Stop using the system — this is dangerous

    • Confirm your test method was correct (e.g. tester injecting current?)

    • Try a different outlet to rule out local neutral/earth issues

    • If still no trip, the RCD is likely faulty and must be replaced

    • Neutral-to-earth faults downstream can mask RCDs — disconnect outgoing circuits and retest at the RCD only

    • Do not reconnect to mains until resolved

  • RCD trips when it shouldn’t (e.g. at ½× test or randomly):

    • Possible background leakage from appliances or wiring

    • Disconnect all loads and retest

    • Inverters may cause DC offsets — this can confuse Type AC RCDs

    • If it still trips at ½× with no loads, the RCD may be overly sensitive and should be replaced

  • Ramp test trips very early (e.g. 10 mA):

    • Cumulative leakage may be present

    • Ensure time between tests for any capacitive charge to bleed off

    • Most testers auto-discharge after IR tests — but RCD tests don’t charge the circuit

  • Trip times are borderline (e.g. 250 ms at 1×):

    • Technically a pass (limit is 300 ms), but keep an eye on it

    • Ageing RCDs may begin to slow down over time

    • Some testers give a warning if the trip time is approaching failure


DC System Testing (12V)

While DC won’t shock you the same way AC can, fires caused by poor connections or excessive voltage drop are a real risk. These tests make sure your 12V system runs safely and efficiently.


1. Continuity & Polarity Check

Why it matters: Ensures your wires run where they should and polarity isn’t reversed.


The steps here are the same/similar to our AC side.


Steps:

  • Power OFF your system

  • Use continuity mode on your multimeter

  • From the fusebox to each device: confirm continuity on both positive and negative wires

  • Also check from each device’s – terminal back to chassis or battery –

  • Check no continuity between + and – unless a device is connected


Tip: You can use a long test lead to buzz out long circuits across the van.


2. Voltage Check & Drop Test (Live Test)

Why it matters:


Verifies that your DC system is delivering expected voltage under load. Excessive voltage drop means poor performance, heat buildup, or hidden resistance in the wiring.


BS EN 1648-2 recommends a max voltage drop of 0.8V under load.


Tools needed:

  • Multimeter (e.g. Fluke 117)

  • Clamp meter (e.g. UNI-T UT210E) — measures DC current without disconnecting wires


Steps:

1. Check base voltage

  • Power ON

  • Measure at battery terminals:

    • 12.0–12.8V resting (lead acid)

    • Up to 14.4V when charging


2. Measure at the load

  • Turn ON a device (e.g. water pump, fridge)

  • Measure voltage at device input terminals

  • Compare with battery reading

    • If device voltage is > 0.8V lower, you’ve got excessive drop


The first two checks can be carried out with a simple multimeter

fluke multimeter
Fluke 117 True RMS Multimeter

3. Use clamp meter to measure current

  • Clip around one conductor only (positive or negative)

  • Read the current flowing during operation (e.g. 8A)

  • Use Ohm’s Law to calculate total circuit resistance:

    R = V / I

    • Example: 0.9V drop ÷ 8A = 0.1125 Ω (anything less than 0.5Ω is acceptable)


A clamp meter is incredibly useful here — no need to disconnect wires or break circuits. You can quickly test any circuit in the van in seconds.

Fluke 325 Clamp Multimeter AC-DC
Fluke 325 Clamp Multimeter AC-DC

4. Check for polarity issues

  • Measure voltage between positive cable and van chassis

    • A negative reading means polarity is reversed


Fixes for high voltage drop:

  • Use thicker cable (e.g. upgrade to 4mm²)

  • Shorten overly long cable runs

  • Clean or replace corroded terminals and connectors


3. Battery Health Test


Why it matters:While multimeters and BMS apps can give you voltage and current, they don’t tell you much about internal resistance, health, or cold cranking performance — which matters for lead-acid systems. For lithium batteries, some testers (like the Topdon TB6000Pro) provide actual State of Health (SOH) percentages. Make sure you don't use a lead-acid tester with lithium battery.


Topdon TB6000Pro
Topdon TB6000Pro is one of the few battery testers that also work with lithium

Steps:

  1. Fully charge the battery to 100%.

  2. Disconnect all loads to get a clean test.

  3. Connect tester clamps directly to battery terminals.

  4. Select battery type (e.g., AGM, LiFePO4).

  5. Run test — the tester will return:

    • State of Health (SOH)

    • State of Charge (SOC)

    • Internal resistance

    • Estimated remaining capacity


Interpretation Tips:

  • For lead-acid: Internal resistance >10 mΩ usually means ageing or sulfation.

  • For lithium: Look for SOH >90%. Anything under 80% might need replacing soon.

  • If a lithium battery fails the test: double-check with BMS before assuming it's toast. Some testers can be inconsistent with lithium.


Shunts & BMS: Many lithium systems already include a smart BMS or a Victron SmartShunt, which also display SoC, voltage, current, and even cumulative capacity estimates. For ongoing monitoring, these tools are excellent.


However, they rely on manual configuration and don’t test internal resistance — so they can miss underlying battery degradation. For a full picture, it’s worth running a standalone tester once in a while.


Fault-Finding & Bonus Tests


Thermal camera sweep:

  • Run your system under full load

  • Use a thermal cam to find hot spots

  • Heat at terminals = resistance = energy loss = danger

flir thermal camera electrical faults
FLIR Thermal Camera

Fuse pull test:

  • Pull one fuse at a time and observe what shuts off

  • Good for verifying wiring diagrams

  • To ensure your MCBs are working, you can also manually flick down the switch. This is by no means a full MCB test, but at least it lets you know the basic functionality is working.


Parasitic draw test:

  • With system "off," use a clamp meter around battery negative

  • Draw should be <0.1A

  • Higher? Something's quietly draining power — track it down


Clamp meter current test:

  • Useful for checking inverter idle draw, fridge consumption, solar input, etc.

  • A must-have tool for diagnosing erratic behaviour


Troubleshooting and Fault-Finding Techniques


Even good installs can fail tests — and that’s the point: better to find issues now than on the road. Here’s how to track them down quickly:


  • Continuity test failures

    • Work backward: check the outlet, then previous junctions

    • Try the half-split method: test halfway along the circuit

    • A poorly attached wire is often the culprit

  • Insulation resistance failures

    • Very low reading = likely a short (e.g. live to earth wiring error)

    • Moderately low = possible moisture or nicked cable

    • Isolate branches to locate the issue; check around holes and sharp edges

    • If L–E is low but N–E is fine, fault is likely on the live conductor

  • High loop impedance (Zs)

    • Double-check with another test or meter

    • Inspect earth connections: plug, cord, inlet, chassis bond

    • Poor chassis bond can add resistance

  • RCD trips immediately

    • Likely a neutral-to-earth fault

    • Turn off all MCBs, reset RCD, turn on circuits one at a time

    • Faulty appliance or crushed cable is common

    • Unplug everything to rule out earth-leakage devices

  • RCD won’t reset

    • Check for reversed neutral/earth at inlet

    • Also check if you're plugged into a supply that already has an upstream RCD

  • MCB trips when something turns on

    • Instant trip = short between live and neutral or earth

    • Delayed trip = overload (too many devices on the circuit)

  • 12V fuse blows

    • Same logic as MCBs — look for a short or gross overload

    • Disconnect loads one by one to isolate the cause

  • 12V device not working / dim

    • Measure voltage at the device vs. at the battery

    • Big voltage drop? Check each section for resistance or bad connections

  • Weird readings or inconsistency

    • Check meter batteries, lead calibration, and test source

    • Inverters can confuse testers — try a pure mains supply if needed


Safety Best Practices

  • Always isolate power when testing with a multimeter or touching wiring

  • Never perform live AC tests unless you're confident, competent, and equipped

  • Disconnect sensitive electronics before high-voltage tests

  • Wear gloves, use insulated tools, and work methodically

  • Use proper cable crimps and torque settings

  • Record test results for each circuit — great for future maintenance


Label everything: Label your fuse box, switches, battery monitor shunts, and wire terminations. It will make testing faster next time — and troubleshooting during breakdowns much easier.


Certified Testing & Documentation

All electrical systems in a leisure vehicle should be tested and signed off by a NCC Certified Electrical Installer for Leisure Vehicles. This ensures the installation meets the safety and performance standards of BS 7671 (Section 721) and EN 1648-2.


As part of this process, the installer will carry out all required tests, including:

  • Continuity

  • Insulation resistance

  • Earth loop impedance (Zs)

  • RCD trip times

  • Polarity and checks


Interestingly, to get your system signed off and approved, installers will only check the AC side of your system, as this is where the real risks lie. This does not mean you should not check your DC side yourself.


Upon successful completion, you’ll receive a formal Electrical Installation Certificate (EIC) confirming the system is compliant and safe. This is a vital document for insurance, resale, and peace of mind.


You can view a sample of the EIC issued under BS 7671 here: Model Forms (IET)


Wrapping Up

This guide doesn’t just show you how to test — it teaches you why each test matters, how to fix common issues, and how to work safely. Even if you plan to get a pro to issue your EIC, running these tests yourself will save time, money, and give you serious peace of mind.


Testing your van electrics properly is one of the best things you can do to avoid fires, shocks, or breakdowns. So grab your meter, double-check your leads, and get started. Your future self will thank you.


 
van conversion electrics guide

Don't forget to subscribe to The Van Conversion Newsletter for everything you need to get started with your own van conversion (we'll send you a free wiring diagram when you join).


If you're looking for some guidance with your van conversion, you might be interested in our book Roaming Home, or in our online course The Van Conversion Mastery Course. You'll learn directly from our founder Shane how to convert a van into your dream home - no prior experience needed. Shane also offers one-to-one consultations, where he'll help you with any aspect of your build in a face-to-face video call. All consultations come with a free copy of Roaming Home and our Diagram Pack.


Finally, our Van Conversion Ultimate Guide lays out the whole van conversion process in easy-to-follow sections with tools, materials, and step-by-step instructions. It's the perfect companion for your van build.


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Until next time.

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