What Happens During an EV Charger Service? A Step-by-Step Guide
You would not drive a car for three years without a service. An EV charger handles significant electrical current every time it operates, and its components experience wear just as any other electromechanical device does. Yet many charger owners — residential and commercial — have never had their unit serviced since the day it was installed.
This guide walks through exactly what a qualified engineer does during a professional EV charger service, what they test, what they look for, and what happens if they find a problem.
Before the Service: Preparation
A professional service begins before the engineer arrives. For commercial installations with multiple chargers, the service is typically scheduled in advance to minimise disruption. Chargers need to be isolated individually during testing, so a plan is agreed to rotate through the units while keeping as many as possible available for use.
For residential chargers, the engineer will confirm the appointment time, check whether the charger is accessible without moving vehicles, and ask whether the consumer unit (fuse board) is in an accessible location — they will need to access it during testing.
The engineer arrives with calibrated test instruments (insulation resistance tester, loop impedance tester, RCD tester, thermal imaging camera), manufacturer-specific diagnostic tools or software, replacement consumables (cable ties, gaskets, terminal screws) and any pre-ordered parts if a known issue has been reported.
Step 1: Visual Inspection
The service starts with a thorough visual check of the charger and its surrounding installation. The engineer is looking for:
Charger enclosure. Cracks, dents, discolouration, UV degradation of plastic components, water staining inside the enclosure (evidence of ingress), loose or missing fixings, and condition of door seals and gaskets. Any damage that compromises the IP rating of the enclosure is flagged for repair.
Charging cable and connector. Outer sheath condition — looking for cuts, abrasion, kinks or UV cracking. Connector pin condition — worn, bent or corroded pins. Locking mechanism operation — the connector should click securely into a vehicle's charge port. Cable strain relief — ensuring the cable entry point into the charger body is secure and not pulling on internal connections.
Mounting and fixings. Wall-mounted units must be secure with no movement. The wall fixings and bracket must be intact. Pedestal-mounted units must be plumb and firmly anchored to their foundation. Any bollard or impact protection must be in place and undamaged.
Cable containment. The supply cable route from the consumer unit or distribution board to the charger is checked for damage, loose clips, missing containment lids and any signs of physical interference.
Signage and labelling. The charger should have correct safety signage, circuit identification and any required warning labels. Missing or illegible labels are replaced.
Step 2: Electrical Testing
With the visual inspection complete, the engineer moves to electrical testing. The charger is isolated from the supply before any test instrument is connected to internal components.
Insulation resistance. The engineer tests the insulation resistance of the supply cable and the charger's internal wiring. This confirms that the insulation has not degraded to a point where current could leak to earth or between conductors. A reading below 1 megaohm indicates degraded insulation requiring investigation. Typical healthy readings are 50 to 200 megaohms for a modern installation.
Earth continuity. The earth path from the charger's exposed metalwork back to the main earthing terminal is tested. This confirms that if a fault occurs, the earth path has low enough resistance for the protective device to operate quickly and disconnect the supply. The IET Wiring Regulations specify maximum values depending on the protective device rating.
Earth loop impedance. Measured at the charger terminals with the charger energised. This test confirms that the total impedance of the earth fault path is low enough for the circuit's protective device (MCB or fuse) to disconnect within the required time — 0.4 seconds for a socket circuit or 5 seconds for a fixed installation, depending on the circuit type.
RCD testing. The RCD protecting the charger circuit is tested at its rated sensitivity (typically 30mA) and at five times rated sensitivity (150mA) to confirm it trips within the required time. For Type A RCDs, which are required for EV charger circuits to detect DC fault currents, the test also includes a DC ramp test. Any RCD that fails to trip within specification is replaced.
Thermal imaging. With the charger energised and under load (either during a live charge session or using a test load), the engineer takes thermal images of all accessible connections — supply terminals, internal bus bars and contactor connections. Elevated temperatures indicate loose connections or degraded components. This is one of the most effective ways to catch problems before they cause damage.
Step 3: Functional Testing
The engineer now tests the charger through its normal operating cycle.
Pilot signal verification. The EVSE pilot signal is the communication protocol between the charger and the vehicle. The engineer verifies the correct voltage levels on the pilot line at each stage: standby (12V), vehicle connected (9V) and charging (6V). Incorrect pilot voltages indicate a control board fault.
Contactor operation. The charger's internal contactor — the relay that connects and disconnects mains power to the charging cable — is tested for correct engagement and disengagement. The engineer listens for clean switching, checks for contact bounce using an oscilloscope if available, and verifies that the contactor de-energises correctly when the vehicle signals end of charge or when the connector is removed.
Load test. A full-power charge session confirms the charger delivers its rated power. The engineer measures voltage and current at the charger output and compares them to the expected values. A 7kW charger should deliver approximately 32 amps at 230 volts. Significant deviation indicates a fault.
Energy meter verification. If the charger has an internal energy meter (standard on commercial units for billing), the engineer compares the charger's reported energy consumption against a calibrated reference meter over a timed test period. Discrepancies beyond acceptable tolerance are flagged for recalibration or meter replacement.
Safety interlock testing. The engineer tests the charger's safety interlocks — the mechanisms that prevent the connector from being energised while unplugged, that de-energise the cable if the connector is forcibly removed during charging, and that shut down the charger if an internal fault is detected. These are critical safety features and any failure requires immediate repair.
Step 4: Software and Firmware
Modern EV chargers are networked devices running embedded software. The engineer checks:
Current firmware version. Compared against the manufacturer's latest release. Outdated firmware may contain known bugs, security vulnerabilities or compatibility issues with newer vehicle models.
Firmware update. If a newer version is available and approved for the installed hardware revision, the engineer applies the update. This is typically done via a direct connection to the charger's service port or over the network. The charger is restarted and re-tested after the update to confirm normal operation.
Network connectivity. For chargers connected to a back-end management platform (OCPP or proprietary), the engineer verifies that the charger is communicating correctly — reporting status, accepting remote commands and transmitting usage data. Connectivity issues are diagnosed and resolved.
Configuration review. Charger settings — maximum current, scheduled charging windows, load management parameters — are reviewed to confirm they match the site's requirements. Settings can drift after firmware updates or power interruptions.
Step 5: Remedial Work
If the inspection and testing identify any faults, the engineer carries out remedial work where possible during the same visit:
- Loose terminals are cleaned, re-made and torqued to specification
- Degraded cables are replaced with manufacturer-approved assemblies
- Failed RCDs are replaced with the correct type and rating
- Worn connectors are replaced
- Degraded seals and gaskets are replaced to restore IP rating
- Faulty contactors are replaced with manufacturer-specified parts
Step 6: Documentation and Handover
The service concludes with documentation:
- Service report detailing every test carried out, results, findings and actions taken
- Thermal images where relevant, showing before and after remedial work
- Test certificates for any electrical work carried out (Minor Works Certificate or equivalent)
- Firmware version log confirming the software version now running on each unit
- Recommendations for any follow-up work, replacement parts due or next service date
How Long Does a Service Take?
- Single residential charger: 45 minutes to 1.5 hours depending on findings
- Commercial installation (5-10 chargers): One full day
- Large installation (15-30 chargers): Two to three days
- Rapid chargers (50kW+): 1.5 to 2.5 hours per unit due to additional high-voltage testing
How Often Should You Service Your EV Charger?
The IET Code of Practice recommends annual inspection and maintenance as a minimum. For high-usage commercial chargers (more than 5 sessions per day), we recommend:
- Full service: Annually
- Visual inspection: Every six months
- RCD test: Quarterly (can be done by a trained facilities manager using the test button)
- Firmware check: Every six months or when manufacturer bulletins are issued
Manchester Compliance Can Help
Manchester Compliance services EV chargers across Greater Manchester for commercial buildings, residential properties, car parks and apartment complexes. Our NICEIC-registered engineers service all major charger brands and carry calibrated test equipment for comprehensive diagnostics.
Call us on 0161 706 1360 to book your EV charger service, or email hello@manchestercompliance.co.uk.
EV charger maintenance and compliance | Princess House case study | EV charger installation costs