How To - Turn Off Or Dim License Plate Lights When Camera Is On/In Reverse

micl9

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UPDATED 5/9/21
Well I am at it again. This time getting rid of the night time camera glare coming off the License Plate Lights. Idea started from this thread: Rear cam vs. License Plate Lights and @Venator68 idea to use a module available in Germany that shuts the lights off when vehicle is in reverse.
Some may say we are bitching about and I am solving a problem that does not need to be solved. BUT for me its the thrill of the chase.

The German module is really just a relay in a waterproof box. So I started thinking that I have some marine grade sealed connector relays I could use, tap off the reverse wire at the tail light and splice the relay into the Lic Plate light wire. After taking a look under the bumper I decided that cutting and splicing into this wire in this location was not the ideal solution. I am sure I could make a watertight splice, but....
The next place to do this is at the BCM where both the reverse light and Lic Plate light wires originate. And as I had already tapped into the reverse light for my Cargo Lights as Back Up Lights mod I am 1/2 way there. I poked around and found the Lic Plate wire, a yellow-violet wire, and its got easy access behind the Vent trim piece. And enough slack to cut and splice in wires, more importantly enough room to splice the wire back together in case something goes wrong to bring it back to stock.
I will say that I don't know the laws regarding having your license plate illuminated while in reverse, but I assume it probably reads in motion at night. So I have come up with 2 plans; 1) Shut the lights off in reverse and hope no one ever notices (get your inspections done during the day!), 2)Dim the lights by reducing the voltage supplied while in reverse. I will start with just shutting the lights off and add dimming later.
After some experimenting I don't think dimming is worth the trouble. In fact I wonder if this is a problem in need of a solution! Pictured below is with LED lights and with lights unplugged. You decide
1620603246326.png

I will leave the info below for those that still want to try this. I will probably still do this as I have all the parts and just need to cut the Lic plate line and run wires to the relay <10inches a way.

Wiring will look like this for shutting the lights off.
1619191175746.png

And like this for dimming. Tom_C gave me some great advice to make this less complicated and use just a series resistor. I had some on hand and 4.7k seems to decrease the brightness alot. We shall see how it looks.
I would welcome any additional input on this!
1619203902171.png

Wires come off of these connectors at the BCM. Follow the harness and look for the wire color. Reverse can be found to the left of the BCM and is Green with Brown tracer. Lic Plate wire is Yellow with Violet tracer located above the BCM behind the vent trim piece.
1619191513615.png

1619191625079.png

1619191653949.png

I will add more detail after I do this myself. But the above pretty much covers it.
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Tom_C

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Nice. I didn't really scrutinize your design, but I would probably say having the voltage divider is unnecessary. Just adding a resistor would accomplish the same thing. The voltage isn't going to remain 'divided' once current starts flowing through 1 resistor, so the divider won't be dividing. :)

And you need to add the caveat that resistor size will depend on current draw (LED vs incandescent)
 
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micl9

micl9

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Nice. I didn't really scrutinize your design, but I would probably say having the voltage divider is unnecessary. Just adding a resistor would accomplish the same thing. The voltage isn't going to remain 'divided' once current starts flowing through 1 resistor, so the divider won't be dividing. :)

And you need to add the caveat that resistor size will depend on current draw (LED vs incandescent)
Thanks for the feedback Tom
That was my original thought, but being an ME not an EE I wasn't sure. And when I Googled it everything directed me to go with a divider. I will play around with it using my 12V source.
I forgot to mention incandescent.
 

Tom_C

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Unnecessary options. Add a switch to disable this for inspections (but your dimming feature solves that problem), OR add a light sensor so it only operates at night (again, dimming feature solves that).

You could also regulate the voltage with a zener circuit (junk design) or a voltage regulator, both of which are probably unnecessary.
 
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micl9

micl9

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Unnecessary options. Add a switch to disable this for inspections (but your dimming feature solves that problem), OR add a light sensor so it only operates at night (again, dimming feature solves that).

You could also regulate the voltage with a zener circuit (junk design) or a voltage regulator, both of which are probably unnecessary.
Could do a switch or a quick disconnect on the ground line to the relay. Adding devices will just crowd the under dash area and add complexity,trying to keep it simple.
I guess i was looking at reducing voltage vs current. I tried some resistors I had on hand; 10k, 4.7k, and 1k. 10k is really dim, 1k was very brite and 4.7k may work. Basically like this
1619195876298.png

Of course I will still need to figure out how dim is acceptable to get rid of camera glare.

I am also thinking about dimming vs off for those times when you back out of the bar and a cop sees you w/o a lic plate light before pulling forward! If its dim might not get noticed....
 


Tom_C

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Yep, I get it. Keep it simple, stupid. I have a tendency to add stupid and unnecessary stuff just because I can :)

As for you LED circuit, in your original drawing the bottom resistor in the divider equals the single resistor in your new circuit. The divider is rendered useless once current starts flowing through the bottom resister, and voltage drop across the bottom resistor takes over.
 

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This was a problem when I replaced the license plate bulbs with led's on my F150, so I left the Rangers bulbs stock, plus they are more inset in the bumper on the Ranger than the F150 bulbs were, may be why I really don't notice them when backing up.
 
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micl9

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This was a problem when I replaced the license plate bulbs with led's on my F150, so I left the Rangers bulbs stock, plus they are more inset in the bumper on the Ranger than the F150 bulbs were, may be why I really don't notice them when backing up.
Yeah same thing happens on the Ranger, not that bad with the incandescent bulbs, but annoying with LEDs.
 

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This was a problem when I replaced the license plate bulbs with led's on my F150, so I left the Rangers bulbs stock, plus they are more inset in the bumper on the Ranger than the F150 bulbs were, may be why I really don't notice them when backing up.
Really? I get an awful glare in the camera when backing up. I wonder if it varies by vehicle for some reason? I'm thinking of adding some tint to the lens to cut down the brightness.
 

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Really? I get an awful glare in the camera when backing up. I wonder if it varies by vehicle for some reason? I'm thinking of adding some tint to the lens to cut down the brightness.
I had glare in my personal XLT truck with both incandescent and LED swapped, not much to speak of in a work XLT with incandescent, and massive glare in a rental Lariat, yet minimal glare in another rental Lariat. i think it really depends on the truck and camera maybe? I am interested in doing this to my truck, no inspections here, as it would greatly help at night.
 

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I had glare in my personal XLT truck with both incandescent and LED swapped, not much to speak of in a work XLT with incandescent, and massive glare in a rental Lariat, yet minimal glare in another rental Lariat. i think it really depends on the truck and camera maybe? I am interested in doing this to my truck, no inspections here, as it would greatly help at night.
Now that is interesting... It makes me wonder if the lens does not sit tight in the same predetermined spot during install and can cast a glare if pointed slightly off. I will have to check and see if it can be adjusted.
 

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Yeah same thing happens on the Ranger, not that bad with the incandescent bulbs, but annoying with LEDs.
Hi Mike. Do you have any update on this? Just curious.
 
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micl9

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Hi Mike. Do you have any update on this? Just curious.
I got off to an ambitious start and even built the dimming harness. But got busy and am now enjoying a little vaca in Chicago. So will get back to it next weekend.
But after doing some trials with tape over the lenses and even removing the bulbs I realized that best solution will be completely turning the lights off. So after updating the harness I will install it and report back.
 
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micl9

micl9

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I updated the 1st post with some with and without lic plate light photos. You all decide if its worth it.
When I have time I will install the relay configuration to shut the lights off when in reverse. No dimming as my testing shows its not that effective.

I am really running out of things to do on my truck!
 

Tom_C

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I updated the 1st post with some with and without lic plate light photos. You all decide if its worth it.
When I have time I will install the relay configuration to shut the lights off when in reverse. No dimming as my testing shows its not that effective.

I am really running out of things to do on my truck!
Thanks Mike. Based on your pics with and without lights, unless other people have much worse glare, I personally can't see where this needs to be fixed. To each their own.
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