Numberplate mounted lightbar - does anyone have experience with them?

Mines not like that at all, over 6000km since I put it on its still as solid as when I mounted it.
Australian laws make it easier to install too, it's counted as a high beam here so it's got a built in relay, it's wired to the battery for power and has a plug and play harness that just connects to the headlight connector.

I don't know if that's allowed over there, but it makes life easy here when connecting them up. You can put a switch on it too if its needed, but lights are easy to set up, and the right mounting set up makes that easy and solid too.

I've got a cheap small light bar mounted on a diy roof bar on my gen3. I think it's 24 inch and provides a lot more light than the standard lights, although I'm not sure about distance as I've not used it in the road, just in wooded tracks.

I didn't bother connecting it to the car lights, just power from the battery and mounted the switch it comes with on the dash

Ok guys, I'm back and this time I'm cutting the nonsense about getting a garage to do it I have bought the numberplate mount and I'm going to try to do the whole thing properly, tapping into the headlight main beam, altering the harness I bought online and using rivnuts for a secure bumper mount.

I might draw a diagram and ask for it to be checked but I think I've got it figured out. Basically we take our negative switched headlight line and put it into one side of the relay (the one that is usually earth but not for this setup). The other side gets its positive input from the switch in the cab which is in turn given power by any ignition live.

The other connections to the relay are just power in from a fused battery connection and then our power out to the lightbar. Earths where required. My switch also has a backlight which can use the same ignition power in from the cabin.

This should mean that that relay is only "on" when the switch in the cabin is closed, the ignition is on and the main beam has been turned on (making the line negative instead of positive).

Two questions to check:

• I am thinking I tap that "ignition live" off the front fog light button ( per skywalker65 in this thread ). If I understand correctly, it goes live with any of sidelights / dipped / full beams - any problems with this or a better way of doing it? This would mean I could run the ligthbar with no keys in so long as I put it on main beams & turn the switch on?
• When the car is totally off, no engine running, headlights off, does the main beam line stay positive? I believe it shouldn't matter in my setup either way(?) so long as the cabin switch is closed or headlight stalk is set to nothing.

Ok, decided to do a quick diagram .

30 - power in from battery
87 - power out to lightbar
86 - control line from negative switched headlight (would usually be earth on normal setups with positive switched main beams)
85 - control line from cabin switch (only +ve when "ignition" / tapped foglight wire is on)

I arrived at a 30A fuse simply because when I did a test wiring up exercise to check the lightbar worked (with the original, unmodified "dumb" harness) it blew out 15A and that's all I had, may try 20A / 25A to see if it can go lower.

(Having issues uploading image, something funny going on with the forum maybe?)
[img]i.imgur.com/TUZUVjt.jpeg[/img]

Found this diagram (from www.narva.com.au/resources/switch-wiring-diagram ) that looks to be identical to my circuit with the exception of a diode being added on the cabin switch control line. Anyone know why that might be? Like I get that it's to force unidirectional current flow (only from the positive switch to the negative high beam) but I wouldn't have thought that necessary.

Edit: A little more thought and I imagine it's a flyback diode to stop voltage spikes when the polarity changes reaching the switch. Really dusting off my old electronics knowledge here...

Job done! Wired everything up as described and to me this is a near perfect job in terms of function. The lightbar only comes on with the high beams ON and the switch in the cabin ON. This means I can safely use the high beam stalk to avoid blinding people at night instead of faffing with a switch.

I did end up going with the numberplate lightbar mount and used rivnuts to secure in the bumper. Here's a random bullet point list of things I did / encountered:

• I did need the above mentioned diode! When not in high beam the wire is live (negative switching) which was causing a "backflow" of current into the illuminated switch. That in turn was causing the unexpected behaviour of making the switch backlight glow when it shouldn't (not good, must have been grounding inside the switch somehow). I ended up buying a pack of schottky diodes off Amazon for £5 (15SQ045, rated for 15A / 45V) and stuck one in series near the switch which prevented the reverse flow. This was only a problem because I have a nice backlit vanity switch which matches the foglight buttons style - the "dumb" switch which came with my wiring loom was fine.
• I ended up using a fuse piggyback off the IG2/SIG for my switch power input (required grinding out a route for the wire in the plastic cabin fuse box). It would've been better to tap into the cabin fog light wire that goes live when side/headlights are on because then my switch would only illuminate with the rest of the dash. The problem is the wire is so thin, short and delicate I didn't want to mess with it. I also didn't have small enough spade terminals to extend it. Tbh the backlight glow is barely visible during the day and any time it would be visible you'd have the lights on anyway - main thing is it turns off when the key is out.
• I put my relay between the driverside headlight and the air filter box. There's a small unused hole that I put a rivnut into. I then ran the cabin switch wire under the air box and battery and through beside the main wiring loom (piercing a hole through the grommet with a skewer). I ran the wire for the lightbar power through the metal headlight surround and down to the bumper, which means it avoids the radiator entirely which is good / important so it doesn't melt!
• The numberplate mounting solution is actually fine and has been stable enough when driving.
• The lightbar beam / intensity is huge and it's just a 20inch cheapo one from Amazon. If it breaks I will not be upside given the price but wow does it light up the road.

Any questions I'll try to answer. The only things I don't like about my setup are 1) I would've preferred the switch to illuminate exactly as the fog light switches do (only when sidelight/headlights are on) and 2) I don't like having a diode in the cabin because they can get warm during use. The diode is well rated for 15A / 45V (and the IG2/SIG is fused at 10A) but still. Regardless, happy to answer any questions!