TheSamba.com :: View topic - Do I need a relay for my LED brake/turn/tail/park lights?

Wed Mar 05, 2014 4:27 am

I'm getting geared up for my wiring install journey and I was wondering do the brake lights need a relay? I think I understand the need for one on the turn signals so it flashes...honestly I dont even know if a flasher is considered a relay or not. Do I need a relay for the headlights since they are not LED?

I did get the No-Load Flasher for the LED turn signals. Can I get another one and use it for my emergency flashers? I was thinking I could go from a constant power to the flasher through a switch on the dash and split from there to the 2 turnsignal wires. Would that work?

I'm going to run a 14 Gang Marine Fuse Block and planning to wire from here to the switch to the various components. Am I missing something or is this a bon fire waiting to happen?

Wed Mar 05, 2014 7:37 am

I have never used a relay for the brake lights. Relays help limit the loads on switches. If you are running LED brake lights (really even if you are not) then there is minimal load on the brake light switches.

When you work out your flashers you need to be sure you keep your left & right turn signal circuits seperate. You can't run 1 wire from the flasher, split it in two, and then hook it to the left and right turn signal circuits. If you do this then both sides will flash when you hit the regular blinkers since the circuits are tied together at the emergency flasher. I would run the flasher through a Dual Make SPST Relay (the 87 & 87a contacts are independent of eachother but are both energized) to make it work.

The only issue you will have with that fuse block is that all of your circuits will be either hot all the time or all will be keyed all the time. It has no provision for splitting the circuits for a combination of keyed AND constant. Its one of the other.

Wed Mar 05, 2014 8:17 am

Thank you very much for the information. I was "planning" to make all the fuses keyed because I will be pulling a separate constant 12 for the amp and will tie in the Emergency Flashers to it. My key has 4 positions (off/acc/run/ignition) with 4 wires (2 Blacks/red/gray) so I will have to figure out what goes where. When I figure out which wire to use, I guess ACC will connect to a relay that feeds power to the fuse block? Thats a total guess.

Will I want a relay for the wipers?

Wed Mar 05, 2014 8:42 am

OF you are going to have all fuses controlled by KEY you need relay, power drain through fuse block is massive at times... With out relay you will probable smoke ignition switch... Other issue is some circuits will not operate when key is off like emergency flasher and headlights... Suggest you use two smaller fuse blocks, one powered all the time (for lamps and em flashers), and one controlled by ignition switch....

Relays are not needed on brake lights.....

Only real issues with LEDS as turn signals, and issue is LEDS typically do not draw enough current (amperage) to operate conventional flashers... Solution may be need for electronic flashers or some other circuit to trigger LEDS as turn signals....

Also using single LED element (for incandescent filament ) for shared stop lamps and turn signals needs to be address by having proper turn signal switch or "circuit" that differentiates on how lamp operates for whatever "condition'" its supposed to be in ( STOP or TURN SIGNAL mode) ...

Dale

Wed Mar 05, 2014 8:45 am

TSFR wrote: I was thinking I could go from a constant power to the flasher through a switch on the dash and split from there to the 2 turnsignal wires. Would that work?

You just need one flasher and one DPDT switch. Then you just have to splice into the turn signal wires after the turn signal switch so they essentially get two power feeds. Both inputs of the DPDT switch are powered off the flasher just like the turn signal switch. Each output of the DPDT switch is tapped into one of the light wires coming from the turn signal switch. When the DPDT switch is off, the left and right light wires are separate and get no power from the DPDT switch and they work with the turn signal normally. When the DPDT switch is on, it connects both light wires together so both lights are powered from the flasher regardless of what the turn signal switch does.

The switch you linked will not work, it's an SPST.

Wed Mar 05, 2014 8:48 am

jhoefer wrote: TSFR wrote: I was thinking I could go from a constant power to the flasher through a switch on the dash and split from there to the 2 turnsignal wires. Would that work?

You just need one flasher and one DPDT switch. Then you just have to splice into the turn signal wires after the turn signal switch so they essentially get two power feeds. Both inputs of the DPDT switch are powered off the flasher just like the turn signal switch. Each output of the DPDT switch is tapped into one of the light wires coming from the turn signal switch. When the DPDT switch is off, the left and right light wires are separate and get no power from the DPDT switch and they work with the turn signal normally. When the DPDT switch is on, it connects both light wires together so both lights are powered from the flasher regardless of what the turn signal switch does.

That will work.... Suggest you use "constant" rate flasher designed to operate anywhere from 2 to 8 bulbs though (truck/trailer towing) ..

Dale

Wed Mar 05, 2014 8:53 am

Be sure you fuse that amp. Also will you have a radio with a clock? If so you will need constant power for that.

You will also need a constant power for your windshield auto park. You might also want to consider constant power for your horn. Most cars have constant power for the headlights but thats a personal choice.

If you power you fuse block (via relay or not) via the ACC switch then nothing will work (including the engine) unless the key is in that position. For keyed power you need to run your fuseblock through the "run" position on your key.

Wed Mar 05, 2014 9:27 am

These are the tails with the park lights on. To simplify things the inside is center is the brake and the outside center is the turn signal. The outside halo isnt as obnoxious as in the pic, but the center is very bright. The front is a built in halo ring around the inside of the headlight.

How do I make this switch work? Already paid for it. :-/

I am DEFINITELY fusing the amp, and using my iPhone as the only source. My new switch does have a park mode so that is great to know!

So whats the point of ACC then?

Wed Mar 05, 2014 9:50 am

Those switches for what purpose?

ACC is usually to run things like the radio if you don't want everything powered up you can just turn the key to acc and run the radio.

Wed Mar 05, 2014 9:57 am

it is only 1 switch (red) and it is for the emergency flashers

Wed Mar 05, 2014 10:22 am

Ok...here is how I would do it. And I am sure in moments others will chime in with better ways.

See the dual make SPST relay here:

http://www.the12volt.com/relays/relays.asp

For wiring...
1. Bring a ground to your switch (needed for the light to light)

Now you will have a power in wire and a power out wire on the switch.
2. Connect the output of the flasher to the 30 tab on the relay
3. Connect the power out wire on the switch to the 85 tab on the relay
4. Connect the 87 tab on the relay to your left blinker circuit (after the blinker switch).
5. Connect the 87b tab on the relay to your right blinker circuit (after the blinker switch)
6. Bring a ground to the 86 tab on the relay.

Now if you want the little light on the switch to flash in harmony with the flashers then you can do this:
1. Connect the output of the flasher to the 30 tab on the relay.
2. Bring a non-keyed power source to the 86 tab on the relay
3. Wire the 87 and the 87b tabs as previously directed
4. On the switch you will have the two wires that have continuity when the switched is pressed (lets call them input and output). On the input bring a ground source. On the output bring that wire (will have "-" signal when the button is pressed) to the 85 tab on the relay.
5. The last wire on the switch (which was the ground on my prior instructions) now gets tapped onto the 87 or 87b wire (it doesn't matter which.

Now the switch light will flash when you push it on.

Wed Mar 05, 2014 2:14 pm

Okay if I'm reading this correctly, all I will need for the Emergency lights are 1 Relay, Mini, Dual87 Contact, SPST, 40A, 12VDC
which has 40 amp rating, will that get the job done? I no longer need a 2nd flasher just for the hazard lights?

What amp size should the Keyed (RUN) relay be for the fuse block? It will run the fuel pump, coil, WS Wiper and remote amplifier wire.
The amplifier is a small Rockford (PBR300X4) made for tight spaces which requires a 30Amp fuse off the battery and 10 gauge wire.

The constant fuse block will power lights, horn, 12volt accessory and dual USB outlet and have no relays.

So far so good? I wanted to say a big thanks for being patient with me on this! :wink:

Wed Mar 05, 2014 4:12 pm

Okay if I'm reading this correctly, all I will need for the Emergency lights are 1 Relay, Mini, Dual87 Contact, SPST, 40A, 12VDC
which has 40 amp rating, will that get the job done? - No..that won't work. See how the 87 tabs are connected on the relay? That will mess things up. You need a relay like the one in the picture where the 87 and 87b tabs are isolated at rest. I am trying to find somewhere that sells them.

I no longer need a 2nd flasher just for the hazard lights?- No...see my last post. You need to take a flasher, run power to it, and then run a wire from the output on the flasher to the 30 tab on the relay.

What amp size should the Keyed (RUN) relay be for the fuse block? It will run the fuel pump, coil, WS Wiper and remote amplifier wire.
- Don't forget , brake lights, turn signals gauges, gauge lights, horn and indicator lights? If so I would look for a 40-50 amp relay. I don't know why you would use one though. Just run an 8 gauge wire from the run on the key to the fuseblock.

The amplifier is a small Rockford (PBR300X4) made for tight spaces which requires a 30Amp fuse off the battery and 10 gauge wire.

The constant fuse block will power lights, horn, 12volt accessory and dual USB outlet and have no relays. - so two fuse blocks? Both those 14 circuit ones you referenced or two smaller ones?

So far so good? I wanted to say a big thanks for being patient with me on this! - No problem

Wed Mar 05, 2014 4:56 pm

http://www.thecustomsabershop.com/16mm-Anti-Vandal-Latching-Red-Ring-Switch-P413.aspx

Buying a new DPDT switch (plus the required 680 Ohm, 1/4 watt current limiting resistor for the LED) will be cheaper than a "Dual Make" relay (if you can find one) required to make your existing switch work.

Wed Mar 05, 2014 5:00 pm

My switch and flasher are already on the way :cry:

Wed Mar 05, 2014 5:10 pm

jhoefer wrote: http://www.thecustomsabershop.com/16mm-Anti-Vandal-Latching-Red-Ring-Switch-P413.aspx
Buying a new DPDT switch (plus the required 680 Ohm, 1/4 watt current limiting resistor for the LED) will be cheaper than a "Dual Make" relay required to make your existing switch work.

I appreciate the idea, is the relay built into that switch? At this point I'm having a hard time nailing down the correct relay anyway. Just out of curiousity is this going to blink when on? The Speedhut guage has the signals built into it but they are a little small.

I never thought emergency flashers would be this complicated, jspbtown thanks for the help and if I can find the right relay I will most likely go that route so I can just use the switch and the flasher I've got coming to me.

Wed Mar 05, 2014 5:18 pm

I'm guessing this wont work because its 24V. If it does, please let me know and I will put an end to this.

Wed Mar 05, 2014 6:54 pm

jhoefer wrote: TSFR wrote: I was thinking I could go from a constant power to the flasher through a switch on the dash and split from there to the 2 turnsignal wires. Would that work?

You just need one flasher and one DPDT switch. Then you just have to splice into the turn signal wires after the turn signal switch so they essentially get two power feeds. Both inputs of the DPDT switch are powered off the flasher just like the turn signal switch. Each output of the DPDT switch is tapped into one of the light wires coming from the turn signal switch. When the DPDT switch is off, the left and right light wires are separate and get no power from the DPDT switch and they work with the turn signal normally. When the DPDT switch is on, it connects both light wires together so both lights are powered from the flasher regardless of what the turn signal switch does.

The switch you linked will not work, it's an SPST.

http://www.thecustomsabershop.com/16mm-Anti-Vandal-Latching-Red-Ring-Switch-P413.aspx

What pins would connect from the back of the switch to the turn signal wires? Where does the required 680 Ohm, 1/4 watt current limiting resistor for the LED go in this mix? Does it do the same thing as the no load Flasher? I am understanding why this would be the easier approach. Sorry, I am so overwhelmed right now. See you guys in the morning. :shock:

Wed Mar 05, 2014 8:11 pm

TSFR wrote: jhoefer wrote: TSFR wrote: I was thinking I could go from a constant power to the flasher through a switch on the dash and split from there to the 2 turnsignal wires. Would that work?

You just need one flasher and one DPDT switch. Then you just have to splice into the turn signal wires after the turn signal switch so they essentially get two power feeds. Both inputs of the DPDT switch are powered off the flasher just like the turn signal switch. Each output of the DPDT switch is tapped into one of the light wires coming from the turn signal switch. When the DPDT switch is off, the left and right light wires are separate and get no power from the DPDT switch and they work with the turn signal normally. When the DPDT switch is on, it connects both light wires together so both lights are powered from the flasher regardless of what the turn signal switch does.

The switch you linked will not work, it's an SPST.

http://www.thecustomsabershop.com/16mm-Anti-Vandal-Latching-Red-Ring-Switch-P413.aspx

What pins would connect from the back of the switch to the turn signal wires? Where does the required 680 Ohm, 1/4 watt current limiting resistor for the LED go in this mix? Does it do the same thing as the no load Flasher? I am understanding why this would be the easier approach. Sorry, I am so overwhelmed right now. See you guys in the morning. :shock:

I believe you want to connect C1 & C2 common (to each other) and then to flasher output... Connect NO1 to left side lamp circuit, connect NO2 to right side lamp circuit... IF my understanding of switch is correct, it should do it for you...

Your 680 ohm resistor should be connected one side to the LED + terminal and other side of resistor to 12volt power source...

Dale

Thu Mar 06, 2014 7:42 am

Quote:
I'm guessing this wont work because its 24V. If it does, please let me know and I will put an end to this.

Nope...see in the illustration how the two 87 tabs are connected? You need them seperate. I know these relays are available...I have bought them before. Let me look around.