Voltage through reverse light when braking

Hey Guys

After some assistance.

Ive installed my reversing camera, all is good except for one thing. When I was braking the reverse camera would activate. So put on the multimeter to find that when reverse engaged i get the 12ish volts. But I also get a 1.7v when not in reverse and the brake is applied.

Does that sound normal?

If so, then can I just add resistors or diodes in series to cancel out that small voltage but will let say more then 2v flow so that when reverse is selected it will activate that way

You've got a dodgy earth somewhere that is making the brake light voltage find it's way to earth via the reversing lamps

Try popping out the tail light assy's and giving everything a good clean, check for corrosion around the brake light bulb holders.
The trailer plug can cause some weird issues as well however that is a longshot but doesn't hurt to check unless you have reverse wired to the Trailer plug then I would head there first

Thanks evil twin. I have the lights that replace the dummy lights and also run reverse and brake lights in my custom rear bar too so its going to be a headache going through checking it all but I will get to that over the coming weeks when I go on holidays.

In the mean time I ran a 3v zener diode reverse polarity so its working great now and only activates with reverse not with braking.

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Originally Posted by meh

Thanks evil twin. I have the lights that replace the dummy lights and also run reverse and brake lights in my custom rear bar too so its going to be a headache going through checking it all but I will get to that over the coming weeks when I go on holidays.

In the mean time I ran a 3v zener diode reverse polarity so its working great now and only activates with reverse not with braking.

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I almost asked if you had modd'd the rear lights in my reply but thought 'Nah, I'll just check on the Trailer Reverse'

Not telling you to suck eggs and if you twigged to using a Zener then you will already know... but.. the Zener is treating the symptom not the problem and it will get worse.
I'd check that rear bar earthing first and when sufficient beers are on hand get into the other light assys

Do you have LED lights/replacement bulbs fitted?

I understand its just a bandaid for now but that's all i had time to do until next week.

Yep I have LED's as reverse brake and indicators in the bar and just normal lights in the dummy replacements.

There is also an electronic brake controller that was on the car when I bought it so im going to have to check it's wiring as well I suppose!

LED's can cause some strange stray voltage issues. Are you still running the incandescent reverse light bulb in the dummy body light? or is it only LEDs in the rear bar now?

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Originally Posted by meh

snip...
There is also an electronic brake controller that was on the car when I bought it so im going to have to check it's wiring as well I suppose!

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Aaaaah, you didn't mention that before either :biggrin:

Brake Controllers and After Market Cruise like Autron are renowned for issues with stray voltages on brake wiring albeit their symptoms are usually opposite to what you are seeing IE the LED's will stop them working correctly.

Anyway I note Dr. Rodney is on the case now so I'll leave you to it as he has a tad more experience than I with these type problems.

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Originally Posted by Yendor

LED's can cause some strange stray voltage issues. Are you still running the incandescent reverse light bulb in the dummy body light? or is it only LEDs in the rear bar now?

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I have fully functional lights that replace the dummy lights and they have normal bulbs. In the rear bar are all LEDs

turns out both of my rear bumber LED's are shorting out - one is working as brake with LED's flickering and the other only as parker. Ordered a new set today so fingers crossed that is the cause :)