Install an LED Light Bar – MG ZS EV

Alert iconPlease Note: The information on this page relates to 2021 models and earlier – the setup described below will not work for 2022 / 2023 MG ZS models with LED headlights. It appears that the LED headlights are setup in such a way that the high beam is activated by a negative switching mechanism – so we are not able to simply use the high beam activation current to switch a relay to activate the light bar. (This is similar to other new vehicles, such as Toyotas – there is a solution, so will post it here when I get it sorted.)

Why a Light Bar?

While our MG ZS EV (2021 model) does have a lot of clever tech stuff embedded, the headlights aren’t fantastic. Replacement headlight bulbs are an option, but don’t really make a great improvement – and cost around $100. (The headlights on later models have been improved with LED bulbs.)

So we have gone down the path of adding an LED Light Bar as shown in the pic below….

Light Bar on numberplate

Scroll to the bottom of the page to see some pics of the light bar in action.

Which Light Bar?

There are plenty of LED Light Bar options available at auto-parts stores. We chose a Kings 12″ Number Plate Light Bar and wiring harness kit.

Kings Light Bar

These are about as cheap as you can get (< $100 here in Australia), reasonable quality for the price, and easy to fit to the existing number plate mounts – no nudge bar or bull bar required. Keep an eye out for the Kings ‘bundle specials’, when the light bar and harness kits are discounted for a day or so.

Normally these light bars are pretty easy to hookup, using a standard “plug ‘n’ play” wiring harness. However, the setup of the high-beam circuitry on the MG headlights isn’t quite ‘standard’, so the connection of the light bar is a bit more fiddly than expected…..

The MG Headlight Setup

Most headlights that I have had any experience with over the years have had either separate high-beam bulbs, or dual-filament single bulbs – one filament for low beam and another filament for high beam. In these scenarios, when the high beam switch is activated in the car, a 12v current flows to the high-beam bulb, or the high-beam filament in a dual-filament light bulb. In a dual-filament bulb, the high-beam filament is slightly offset in relation to the reflector, projecting the beam slightly further than the output from the low-beam filament.

In the MG, there is no high-beam bulb, and only a single filament in the headlight bulbs. When the high-beam switch is activated, the reflector moves a little to throw the beam a longer distance.

Filament and beam setup

Unfortunately this defeats the well-meaning purpose of the plug ‘n’ play headlight bulb adaptors, which use the 12V current to the high-beam bulb/filament as a trigger to illuminate the LED Light Bar. But all is not lost….

Installing the Light Bar

This part of the process is straightforward – remove the number plate, fit the Kings plate holder and mounting bracket, then re-attach the number plate to the Kings plate holder.

I attached the Kings plate holder to the original number plate holes on the car, using the second row (from the top) of pre-drilled slots in the Kings plate holder. This lifts the bar mounting brackets high enough to improve access to the light bar adjustment screws, for later alignment of the beam using the supplied Allen Key. I also added a couple of screws to the bottom of the plate holder. to provide more stability when the light bar is attached.

Refit the number plate (sharing screws with the Kings plate at the top), attach the light bar to the number plate mounting bracket, then feed the attached cable under the bumper and through to the engine bay. (This required temporary removal of the plastic cover plate under the vehicle to provide hand access to pull the cable through.) Neatly attach the cables with cable ties.

Light bar cable

Part 1: Electrics – Preparing the vehicle

Most 3rd party light bars are supplied with a wiring harness that includes a piggy-back connector to attach to the socket on the back of a headlight bulb – either a 3-pin twin-filament bulb or a 2-pin high-beam bulb. Using this connector, the light bar is activated when 12V current is switched to the pin for the high-beam bulb, or the high-beam filament in a single bulb headlight.

As discussed above, the MG has a single headlight bulb, but it is only a single filament bulb with no pin to activate a high-beam filament. There are only two pins on the bulb connector: +ve and earth. The headlights are either ON or OFF – there is no high-beam current available at the bulb to tap into to activate the Light Bar. This rules out being able to use the simple plug ‘n’ lay option of a piggy-back bulb connector.

Important note: Proceed only if you feel confident in tampering with the vehicle wiring, and you are able to competently use a soldering iron and associated tools. If this is not the case, your local auto electrician will be able to complete the procedure outlined below in under an hour.

There is a multi-cable socket on the side of the headlight housing, bringing electrical current to the headlight. One of the wires in that socket connects to the high-beam adjusting mechanism in the housing – and is activated with 12V when the high-beam switch on the column stalk in the car is switched to the high-beam position. We can tap into this circuit to activate our Light Bar….

Disconnect the socket by releasing the white locking clip on the top of the socket. Peel back the split conduit cover to expose the cables running into the connector.

A little bit of multimeter exploration soon identifies the live high-beam cable – in our car (MY 21.5) it is a blue cable with a yellow trace, on the top row of the socket (the side the locking clip is on), second from the end. (This may or may not be the same in every MG – double-check with a multimeter on your car before proceeding!)

Identifying the high beam cable

We need to remove a section of the insulation from this cable, to expose the copper wire. This requires some careful trimming work with a packing knife….

Removing insulation

This exposed copper wire can then be ‘tinned’ with solder.

Now we need to prepare the headlight/relay connecting plug, supplied with the Light Bar wiring harness.

Part 2: Electrics – Preparing the relay connector

The Kings Light Bar wiring harness includes a couple of ‘piggy-back’ connectors, each designed for different vehicles – one with a 3-pin headlight adaptor, the other with a 2-pin headlight adapter.

These adaptors are designed to fit between the headlight bulb and the incoming electric current, to pickup the 12V high-beam current, and use this current to activate the relay (supplied with the wiring harness kit) which will then connect 12V from the battery directly to the LED light bar.

Both adaptors/connectors include a 2-pin power socket with red and black wires. These wires send 12V high-beam current to the relay when activated with current from the high-beam switch. We want to use one of these connectors, but not the headlight socket.

Use side-cutters to separate the connector, and it’s cables, from the headlight socket….

Cable clip after cutting

Strip 15mm of insulation from the red cable, and solder an eye connector to the black cable…

Connectors on cables

The relay connector cable is now ready to be connected to the vehicle wiring harness….

Part 3: Electrics – Connecting to the vehicle

Three parts to this section…

1. Mount the relay

The relay is best mounted close to the battery. I used the wiring terminator on the battery’s negative terminal as a mounting point for the relay, also using this point to connect the -ve cable from the relay and the -ve cable from the headlight activation cable (to which we soldered the eye terminal above)..

Relay connected to battery

This location is close enough for the +ve (red) relay cable to connect to the +ve terminal of the battery – but don’t connect this cable just yet!

2. Relay cable headlight activation connection

Working with the purple headlight plug removed from the socket….. Twist and solder the previously-prepared headlight activation cable to the high-beam activation wire that we prepared on the headlight wiring harness.

Connecting to harness

Insulate the soldered joint, restore the cabling conduit, and re-join the purple connector plug to the headlight socket.

3. Connect the Light Bar

When you are confident that all cabling is in place, connect all the plugs, then attach the red cable from the relay to the +ve terminal of the battery.

The connections should look like this….

Light bar cabling schematic

Neatly cable-tie all the cables to existing tie points, and in neat bundles where the cables are longer than required.

The cabin switch cable can be left loose for now. However, if you turn the rocker switch ON, you should be able to power up the car, activate the high beam and check that the Light Bar works! (The car will need to be turned on for the headlights to operate.)

Part 4: Install cabin switch

  1. Finding a path through the firewall – After a little bit of hunting around I found an oval rubber cover on the driver’s side of the engine bay that provides cable access through the firewall. I removed the cover, drilled a 10mm hole through the bottom left corner, fed the switch cables through the hole, then re-fitted the cover. Tidy up the cable installation with cable ties to existing mounting points.
    Switch cable through firewall
  2. Using an alternate (round) switch – The switch supplied with the Kings wiring harness is a large rectangular switch, which is a pain to mount. The local auto parts store supplies switches with a round barrel that are easier to mount on the dash – just need to drill a round hole!
    Switch - round fitting
  3. Locating the switch in the cabin – I located the switch below and to the left of the steering column. There is an area here that can be drilled, and is accessible from the rear to connect the switch cables.
    Switch on mounted on dashboard

On the Road

Low Beam

High Beam

High Beam plus Light Bar