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Four Brake lights and turn signals

redheadedrod

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I would make a couple suggestions for this mod...

You may want to do it with LED's to insure you don't overload anything...  Will probably work fine but LEDs take next to no power and are brighter than factory lighting.

I would leave the wiring as the original poster has it but add a fuse and diode inline from the trailer.

If the fuse blows then your factory setup will still work as designed and you are just loosing the brake lights on the turn signals.
The diode would be there to prevent the stock system from feeding a trailer if it is connected.

I would NOT disconnect the turn signal from the normal feed because if the truck is ever used to tow and you blow the trailer fuses under the hood you lose your turn signals. Diodes and fuses are cheap... Make use of them.. ;)

Rodney
 

Avalanche2003SS

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Hi all! First time posting, long time follower... Would you be able to just use 2 diodes per side and just cross over the turns and brakes with out problems? I have LEDs so there would be less draw. I was thinking of trying this tonight. ??? Thanks!
 

redheadedrod

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You COULD do it with just 2 per side but I strongly suggest the method I mentioned because if you lose your trailer lights you lose your turn signals while braking.

The top light is normally the brake light (2002-2006). You can put a diode between the normal brake light feed and the brake light and then hook the normal turn signal feed to the Brake light as well.

Then the bottom light just gets connected directly to the trailer lights but if you lose your trailer lights you lose your bottom lights as already mentioned. The top will still show turn signal but when the brake light is on it won't show the turn signal on that side anymore.

 

Avalanche2003SS

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I meant taking a diode from the brake to the turn and another diode from the turn to the brake. I can't post pictures of the layout yet, but it would make an X pattern to the original layout and not use the trailer harness at all. I will pick up some diodes tomorrow and try it.
 

redheadedrod

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Won't work... Depending on how you do it you will lose your turn signals when your brakes are on or you will have turn signals that flash both sides.
 

Avalanche2003SS

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So there really isn't a way to have have all 4 lights used for brakes and turns and have the turns override the brakes like the 07+?
 

wyotonka

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Avalanche2003SS said:
So there really isn't a way to have have all 4 lights used for brakes and turns and have the turns override the brakes like the 07+?
Taggin this, I have been wanting to do this so (in theory) both vertical lines of leds on my truck light up.
 

TheAtheistReverend

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There is always a way. The question is is it a good way?

I am thinking I will try LEDs and just wiring them in from the trailer lights. The trailer lights are set up to control a dual filament-single bulb setup. With LEDs, there will be more than enough room to run both lights per side. Just have to make sure I am not over loading the circuit if and when I hook up a trailer.

Someday... :p
 

redheadedrod

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Avalanche2003SS said:
So there really isn't a way to have have all 4 lights used for brakes and turns and have the turns override the brakes like the 07+?

Not without using the trailer lights...

I have the verticle LED lights in my truck and did this mod the way I suggest...

I used 4 diodes and a fuse on each side of my install... Original posting calls for 3..

You COULD do this mod with just 2 Diodes... But I STRONGLY suggest not.. I used 3 amp Diodes in my install. I would not go lower. Since I am using LED's the 3amp diodes are over kill. (I put my Load resistor for the brake lights upstream from the diode so the diode would not have to carry the current. Without the load resistor on the passenger side brake light the cruise control won't work.)

3amp x 12 volts = good for 36 watts...

The Mandatory Diode would be placed between the normal Brake light feed and the top (Brake) light high filiment. This prevents the turn signals from backfeeding through the brake system and flashing both lights. You attach the line from your turn signals at the outlet of the diode to the top light. (Line on diode pointed towards light)

The first optional Diode would be on the output of the normal turn signal lines. Since you cut the line for the normal turn signals to the bottom (turn signal) light you still should use the diode between the turn signal supply feed and the top (brake) light. This will prevent the brake lights from back feeding into the turn signal system. I call this optional because the system may already be protected against backfeeding but it still is a good idea to use it and the original instructions call for it and don't call it optional.

The second optional diode is the one from the turn signal feed to the bottom (turn signal) light. Since you will be feeding this from your trailer light system you don't need to feed from the normal feed line. HOWEVER, if you ever have an issue with the trailer lighting you will lose your bottom lights... I STRONGLY suggest installing this diode so if you DO lose the trailer lighting you still have your OEM turn signals...  The previously mentioned optional diode then becomes mandatory from the turn signal feed to the top (brake) lights.

The 3rd optional diode and the optional fuse I used from the trailer lights to the bottom light. The fuse will blow if there is an issue and is a good idea regardless since you are tying two systems together. You can also then pull the fuse if you decide not to attach the trailer light to your bottom light. (Because an issue with trailer or something.)  The diode is placed to prevent any sort of back feed from the OEM lighting to the trailer lights. This is in case you are pulling a trailer and you have an issue with the trailer lighting that blows a fuse on the trailer. You won't feed from the tail light system to the trailer system which will protect the tail light system. (Of course if you don't use the second optional diode then this diode is not going to do anything.)

On my system I have LED tail lights... I feel confident this system will be durable and will work. If I ever have an issue with trailer lighting the failsafe is for my turn signals to work as they always did and the brakes will as well. I just have the added turn signals when the brakes are not applied...  I would not want to do this on an OEM system with standard bulbs. The power requirement of pulling twice the power through the same harness may eventually cause harness failure that will be hard to diagnose.

As it is the LED's are MUCH less power hungry than standard bulbs and should not see any issues...

 

qreaigh

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Is it necessary to have a wire going to the trailer harness from the brake wire like the diagram shows? I don't see the need for that wire.
 

redheadedrod

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qreaigh said:
Is it necessary to have a wire going to the trailer harness from the brake wire like the diagram shows? I don't see the need for that wire.

The top light should be fed from both the normal top light feed and the normal bottom light feed with Diodes to prevent backfeeding the lines. No other lines go to the top lines.

The bottom light CAN just feed directly from the trailer lights but I suggest combining with the normal bottom feed with diodes preventing back feed in case the trailer feed gets a blown fuse so you still have lighting.  If the trailer feed blows a fuse you lose the brake light function on the bottom but still maintain the turn signal.

There should be no other lines going anywhere else. Without looking at the original drawing I am not sure what you mean. Should not be any trailer lines going to the top light at all.

Rodney
 

qreaigh

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Link to drawing  http://www.chevyavalanchefanclub.com/cafcna/index.php?action=dlattach;topic=16152.0;attach=7421;image

The way I see it once you link the top brake wire to the bottom light (with diodes)  you shouldn't have to run a wire to the trailer harness.
 

redheadedrod

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That drawing is correct and is the proper way to do it. You can also put a diode and fuse from the trailer line with the line facing away from the trailer harness.


The hookup in that drawing will allow the top light to flash when turn signals are on and no brakes.

The bottom turn signal will feed both of the lights. 

By hooking up the trailer lights you are allowing your normal turn signals to also act as brake lights when not turning.

Yes this configuration does also feed the trailer light to the top light but that is fine. You COULD have the normal turn signal light feed the top light only and then hook the trailer light directly to the bottom light without the normal turn signal feed but you would loose your bottom light all together if the trailer harness blows a fuse.

Rodney
 
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