It's a common thing to see LEAF headlights upgraded from Halogen to LED ones. Also sometimes people do the opposite thing for couple reasons. First, if vehicle has been involved in an accident and headlights need replacing, sometimes LED ones are hard to source or way to expensive compared to new Halogen. In my case after moving to live in Germany I had to register my RHD vehicle here, so the headlights had to be changed before I could pass the road worthiness test. I was unable to source used LED headlights and new ones were way to overpriced. So I ended up by downgrading them to Halogen. Physically it's a straight forward job to swap different type headlights, but connectors have to be swapped and wiring modified. Easiest way is to pull terminals out of headlight plug and swap the plug itself on new headlight with the old plug.
Please note that this information is only valid for ZE0 vehicles sold in Europe. US models use different bulbs and probably different wire configurations.
So first lets have a look what every wire does on these two different type headlights:
As you see plugs and wire colors differ. Also switching of high and low beam differs between those two types. Vehicle, which had LED lights fitted from factory, leaves LED low beam on even when high beam is switched on. And the opposite way for LED headlights fitted to non LED model.
So the next picture shown what you need to modify to fit LED headlights to LEAF that came with the Halogen headlights. As you see in order to have LED low beam always on you will have to use relay and make a new power feed from battery to the relay for low beam while high beam is on. IT IS VERY IMPORTANT that you use 15A fuse as close as possible to the battery or where you taking this power feed from. Also each headlight MUST have separate fuse. This is legal requirement. So if one side fails the other would not be affected. Green and Orange wires coming from LED control module must be left disconnected.
Next picture shows how to wire the Halogen headlight to the vehicle which had LED headlights fitted. As LED models leave low beam on while high is switched on, wiring needs to be modified. If you won't do this modification halogen bulbs will keep failing and headlight reflector will get damaged eventually by excessive heat. Also you will need 220Ohm resistor to be fitted as shown in this picture. This needs to be done so no headlight fault light is displayed on instrument cluster.
Another difference between these two types is how headlight leveling is handled by vehicle. In Europe almost all vehicles with Halogen headlights have manual height adjustment, while LED ones got automatic adjustment. But the plugs on headlights are exactly same. So it's only up to inspector who will be checking your vehicle on the next MOT if he likes that leveling is not up to standards. Strangely enough German strict inspectors turned a blind eye on mine upgrade without properly sorted headlight leveling.
