Reverse Light Issue

[DougM55]

Just thinking out loud... I think I'd power the aux leds with a direct connection to the battery (maybe though 7-pin 12v). Then I'd use a relay powered by the stock reverse lights and switch where the relay closes the ground to the aux leds. I'd put diodes on the trigger wires that feed the relay from the stock reverse lights and switch so as to not activate the stock reverse lights when flipping the switch for the aux leds.

I'm not very familiar with 12v wiring but I'm pretty sure using a relay would fix most of your issues.

If you're using an ON/OFF/ON switch then you'd do something similar but one branch of the switch would receive power from the stock reverse lights to feed the relay trigger. With this setup you could prevent the aux leds from coming on in the event that you only wanted your stock reverse lights to come on while backing.


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[jgruberman]

Thank you. Makes sense. Do you happen to know which wire that is in the harness? If not, no biggie... I'm sure I can find out, just thought I'd ask

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[jgruberman]

Just thinking out loud... I think I'd power the aux leds with a direct connection to the battery (maybe though 7-pin 12v). Then I'd use a relay powered by the stock reverse lights and switch where the relay closes the ground to the aux leds. I'd put diodes on the trigger wires that feed the relay from the stock reverse lights and switch so as to not activate the stock reverse lights when flipping the switch for the aux leds.

I'm not very familiar with 12v wiring but I'm pretty sure using a relay would fix most of your issues.

If you're using an ON/OFF/ON switch then you'd do something similar but one branch of the switch would receive power from the stock reverse lights to feed the relay trigger. With this setup you could prevent the aux leds from coming on in the event that you only wanted your stock reverse lights to come on while backing.


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This makes sense too busy but where would I put the relay if they need to be close to the battery but also tap into the reverse harness?

Do you have any additional details about the diodes? Not too familiar with them and their purpose. Thanks!

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[catch 22]

If your using the factory reverse taillights to power the LEDs in the bumper. Try using the reverse wire(center pin) from the 7 pin trailer brake connector instead. The added load might be messing with the CANbus monitoring.

ding ding ding, we have a winner!

This is what I did........no problems, no errors.

 

[jgruberman]

ding ding ding, we have a winner!

This is what I did........no problems, no errors.

What do I do with the factory harness since I replaced that location and dont actually have bulbs there anymore? Resistor?

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[sbarron]

You lost me at "connections together that were just with electrical tape"
and "cheapy meter"...

Where did you "cut off" your factory reverse harness? Were there only two, or more, wires at that point?

Reading your symptoms, I'm leaning towards a bad ground for the LED's themselves. It's the place closest to the initial symptom, (the LED's not coming on", and the only thing that would be common to both the factory reverse circuit and your independent switched circuit. Start by checking your ground connection here " I just connected the negative from the LEDS to the negative that was running to the reverse bulb"

If you can, check continuity (not resistance) downstream (towards the LEDs) of the ground wire to a good chassis ground point.

 

[jgruberman]

You lost me at "connections together that were just with electrical tape"
and "cheapy meter"...

Where did you "cut off" your factory reverse harness? Were there only two or more wires at that point?

Reading your symptoms, I'm leaning towards a bad ground for the LED's themselves. It's the place closest to the initial symptom, (the LED's not coming on", and the only thing that would be common to both the factory reverse circuit and your independent switched circuit. Start by checking your ground connection here " I just connected the negative from the LEDS to the negative that was running to the reverse bulb"

If you can, check continuity (not resistance) downstream (towards the LEDs) of the ground wire to a good chassis ground point.

I cut off the factory harness and wired the factory negative and positive to the negative and positive from the LED.

They are coming on now in reverse but not working at the switch(which I diagnosed as a bad switch and need to replace today.

The current problem is the bulb out and if I wire the LEDs to the trailer reverse and ground them... What do I do now with the factory harnesses? (even if I splice them back in)

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[crash68]

The current problem is the bulb out and if I wire the LEDs to the trailer reverse and ground them... What do I do now with the factory harnesses? (even if I splice them back in)

Either put the factory back in with either regular bulbs(or CANbus LEDs) or use resistors in place of the factory lights.
The factory locations is where the CANbus monitors for bulb out, the trailer plug doesn't care if anything is hooked up or how much it draws(up to when the fuse blows)

 

[jgruberman]

Either put the factory back in with either regular bulbs(or CANbus LEDs) or use resistors in place of the factory lights.
The factory locations is where the CANbus monitors for bulb out, the trailer plug doesn't care if anything is hooked up or how much it draws(up to when the fuse blows)

Any certain kind of resistors? Like any specific rating?(if such a specification exists)

I have a set left over from my HID headlight install

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[crash68]

Any certain kind of resistors? Like any specific rating?(if such a specification exists)

I believe they make ones sized for the reverse light bulbs. The resistor needs to be sized to mimic the current draw of the standard incandescent bulbs. The ones for headlights might be "too big" (meaning they pass too much current)

 

[jgruberman]

I believe they make ones sized for the reverse light bulbs. The resistor needs to be sized to mimic the current draw of the standard incandescent bulbs. The ones for headlights might be "too big" (meaning they pass too much current)

Is there a specific draw or amperage or current that I need to get the resistors to match in terms of an actual number?
Any certain watts or ohms?

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[crash68]

The reverse bulb I think is a 921 draws 1.4 Amps @12v an equivalent resistor is 8.5 ohms rated for no less that 17 watts(probably more like a minimum of 20-25 ohms)

or there is this from the Ram Body builder:
https://www.google.com/url?sa=t&sou...1aAElPdeWRBzb3sMg&sig2=p1cbFT4EbGI3H2dqNZZ1jg

 

[jgruberman]

So based on what this is saying... I wire the positive and negative from the harness to the positive and negative of the LED and also run one side of the resistor to the positive connection point, and another side of the resistor to the negative connection point. Right?

Or do I just wire the LEDs to the trailer harness and install the resistor in place of the factory harness?

Or at this point, does it really come down to trial and error?

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[Rzrman328]

I have my LEDs positive wired into trailer harness and negative grounded to frame.

Are you trying to install resistors on the LED pods themselves? Shouldn't need to.

Have you already installed resistors on the led's in your oem reverse or is this what your trying to figure out?

 

[crash68]

do I just wire the LEDs to the trailer harness and install the resistor in place of the factory harness

^^^ this ^^^
You'll need a resistor for both sides (left & right) The factory locations need to be separate, don't use the factory grounds for the bumper LEDs, attach straight to the frame.

 

[Rzrman328]

^^^ this ^^^
You'll need a resistor for both sides (left & right) The factory locations need to be separate, don't use the factory grounds for the bumper LEDs, attach straight to the frame.

Exactly.

 

[jgruberman]

^^^ this ^^^
You'll need a resistor for both sides (left & right) The factory locations need to be separate, don't use the factory grounds for the bumper LEDs, attach straight to the frame.

Got it. To clarify:

LEDs
Connect positive from both LEDs to trailer reverse. Ground both LED negatives to the body somewhere close.

Reverse Wiring
Connect one side of resistor to factory positive and other side of resistor to factory negative. Repeat this for both sides.

Right?? Think I'm finally set.


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[crash68]

Right?? Think I'm finally set.

Yeap!!

 

[blackbetty14]

Stop doing it the half ass'd way. Real connections require watertight splices/solder with heat shrink. Stop everything your doing, ditch the resistors and crap. Run a 14 gauge or 12 gauge wire from a 12v battery source (trailer hitch plug works too) to a 4 or 5 pin relay (waterproof if you want it to last) use a short ground for the relay and use the backup lights to trigger/energize the relay this providing the 12v for your LeD cubes. Then use the rocker switch to activate the relay as well by sending a low amp 12v to the relay. You will prob need a double throw relay but the total cost should be less than $20 for everything waterproof. You should run a 10-15amp fuse in the 12v main power source.

That way no resistors are needed and no canbus related issues. Tapping into the light wiring on these trucks is a nightmare as they are also finiky. The relay energizing power would be mili amps to trigger the relay so the headlight wiring canbus system wouldn't even know.

Do it the right way and do it one time and save your self the headache of all this. It should be very easy since you already ran the wiring for the rocker switch which would be the most annoying part.

 

[jgruberman]

This has been fixed. Resistors to the factor harness location, led running from reverse wire in trailer connector

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