Wiring question

[167]

I want to use some rear facing red LED’s as brake/warning lights.

If I set the flash pattern to steady and use an external flasher, I’m pretty sure I can just wire the hot wire to the brake wire and the ground to the flasher (pretty sure the one I have pulses the ground and not the hot). My question is do I need to do anything to prevent it from backfeeding in either setup?

Thanks.

 

[C17LVFD]

Unless the light is specifically made as a brake/turn signal... you’ll need diodes to isolate how the power flows into the light so you don’t get backfeeding.

If the external flasher is negative, you’ll also need a steady positive wire to the light head when the flasher is active. Diodes are your friend for this.

Good luck,
Seth

 

[167]

Unless the light is specifically made as a brake/turn signal... you’ll need diodes to isolate how the power flows into the light so you don’t get backfeeding.

If the external flasher is negative, you’ll also need a steady positive wire to the light head when the flasher is active. Diodes are your friend for this.

Good luck,
Seth

Okay thanks. I've never messed with diodes, but I'll see what I can figure out.

 

[Evtech161]

are you sure your vehicle switches on the ground? i would use a volt/ohm meter to check the circut. what type of vehicle is it?

 

[167]

are you sure your vehicle switches on the ground? i would use a volt/ohm meter to check the circut. what type of vehicle is it?

Not the vehicle, the LED flasher utilizes the ground wire to flash.

 

[buddek09]

You need to verify that the light will see ground with the flasher off. More than likely the flasher only switches to ground when activated instead of breaking the ground connection. If this is the case you will need a relay to switch between ground and the flasher so the brake lights will work. At that point it might be easier to just get a positive flasher, like the Feniex Flasher, or a taillight flasher, like ERM's Programmable Taillight Flasher.

 

[167]

You need to verify that the light will see ground with the flasher off. More than likely the flasher only switches to ground when activated instead of breaking the ground connection. If this is the case you will need a relay to switch between ground and the flasher so the brake lights will work. At that point it might be easier to just get a positive flasher, like the Feniex Flasher, or a taillight flasher, like ERM's Programmable Taillight Flasher.

Okay, I see what you're saying. Thanks for the heads up. I can handle and have done several straight forward easy wiring setups, but I start getting lost in relays and diodes.....

 

[167]

For the record, I'm not interested in them working as tail lights, just brake/warning.

It's an 06 Dodge 2500 Mega Cab, 5.9L

 

[buddek09]

Yes I know that but they refer to the flashers for the brake lights as taillight flashers.

 

[167]

Yes I know that but they refer to the flashers for the brake lights as taillight flashers.

So let me ask you this, or any other installer, evidently 2006 is when Dodge stopped using traditional fuses and relays and started controlling wires through the ECM. Will a headlight flasher work, or no?

 

[buddek09]

So let me ask you this, or any other installer, evidently 2006 is when Dodge stopped using traditional fuses and relays and started controlling wires through the ECM. Will a headlight flasher work, or no?

Yes, a headlight flasher will work, just make sure to get an isolated flasher. It eliminates the need to use diodes and ensures you won't have feedback on the factory wiring, potentially frying the ECM. The only time a headlight flasher will not work is if the vehicle has the bulb out warning system, or HIDs.

 

[167]

Yes, a headlight flasher will work, just make sure to get an isolated flasher. It eliminates the need to use diodes and ensures you won't have feedback on the factory wiring, potentially frying the ECM. The only time a headlight flasher will not work is if the vehicle has the bulb out warning system, or HIDs.

What I currently have is a Whelen ULF2150A. Will that work? If not, I am familiar with "isolation" models from Sound Off.

Thanks.

 

[buddek09]

What I currently have is a Whelen ULF2150A. Will that work? If not, I am familiar with "isolation" models from Sound Off.

Thanks.

I couldn't find any info on the ULF2150A. I think you meant UHF2150A, if so then yes that will work because it's an isolated model.

 

[firemedic10584]

I didn't read too far into your thread - but I'm just throwing this out there. I use 2 Feniex Fusions to accomplish what you're wanting to do. They have 2 modes. I have mode 1 set up to flash in warning mode and mode 2 set to steady burn which is tied into my brake lights. So, when my emergency lights are activated, they flash then when I apply the breaks, it overrides and goes to steady burn red until I let off the brake again. No diodes, no relays. Not sure if this is what you're trying to do but maybe it'll help.