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Discussion Starter #1
I got a LED light bar to be mounted below the tailgate. It is advertised as having a running/parking light function (all red LEDs lit at low brightness), a brake light function (all red LEDs lit at full brightness), sequential amber turn signal function, and amber hazard signal function. It has a 4-pin connector to plug into the trailer hitch connector or can be hard-wired into the taillight wiring.
I first plugged the light bar into the trailer hitch connector and could only get the running and brake light functions, no turn signals or hazard lights.
I spliced the light bar wiring into the truck wiring and got the same results. Tried it with and without resistors.
During this process I tested the wiring at the back of the truck and I have correct voltage to running, brake, turn and hazard lights (intermittent voltage to turns and hazards).
The vendor told me to connect the light bar directly to the battery to determine if the bar was defective. I connected the ground lead to the negative post with a jumper and then connected each of the other leads one at a time with another jumper. Running and brake lights worked as they had when connected at the rear of the truck. When I connected each of the turn signals I got a brief amber signal that immediately changed to all red at full brightness. Same result on hazards. If I touched the jumper briefly to the positive post I got amber lights.
The vendor then said I needed to change my flasher to an electronic flasher to make the light bar work. Since our trucks do not have flasher relays (controlled by the BCM) that is not an option.
Looks like I’ll be returning this light bar.
 

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That sucks. That was going to be a fun mod. I think the light bars are cool. I also like the LED tail lamps I have seen. I have the LED high mount stop lamp and the tail lamps are in my Truck Stuff list on Amazon. But $150 to replace perfectly good lamps isnt making the most sense these days.
 

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Discussion Starter #3
The LED light bar and a LED high mount stop light we’re both Christmas presents (from my shared Amazon wish list). The stop light works great except for that one white LED in the bed light portion that is dead (should have powered it up before I stuck it on the truck).
The light bar guy said the flasher has to discharge all the voltage between flashes (0 voltage) for the LEDs to work. I think it may have something to do with the sequential function. I have LED “bulbs” in my tail, brake and turn lights (with resistors) and they work great. Also put LEDs in the back-up lights and they really make a difference in visibility. Total was about $45.00 including the 5watt resistors from Amazon. The white ones were rated higher lumens than the reds but all of them are a lot brighter than the incandescent bulbs they replaced. I had already replaced the taillight housings because one was cracked (also got them on Amazon).
Since I can’t get it to work, the light bar will be returned.
 

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Before returning the light bar you could check with a local shop that installs remote starters for some help . Some places like that can be very helpful in situations like yours . They may advise you for free or they can install for you . As always , this is a cost versus reward thing based on how badly you want those lights to work .
 

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Discussion Starter #5
“Before returning the light bar you could check with a local shop that installs remote starters for some help . Some places like that can be very helpful in situations like yours . They may advise you for free or they can install for you . As always , this is a cost versus reward thing based on how badly you want those lights to work .”

Old Time - we have a very capable shop nearby that does alarm, remote start and audio upgrades for dealers in the area. We used them to install remote start and a back-up camera in my wife’s car and I wouldn’t hesitate to use them again if I thought they could correct the problem.
However, I don’t believe this is an install issue as the vendor did not indicate there was anything wrong with use of the trailer wiring connection or with splicing directly into the wiring harness. He indicated that the problem is with the flasher (in the case of our trucks, the BCM) “signal”. The way he explained it, the voltage must drop to zero between flashes to turn the LEDs off as the voltage required to light the LEDs varies more widely than that required for incandescent bulbs. I checked the voltage on the turn signal leads with both digital and analog voltmeters and found that the voltage does not appear to drop completely to zero. If we had conventional flasher relays in our trucks I could install an electronic flasher relay and solve the problem, but that’s not an option.
And there is the cost/benefit ratio as you noted. I like the look of these light bars but I have more time invested trying to get this thing to work than it‘s worth to me at this point.
 
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You can "add" relays into the turn/brake wiring that would be fired by the BCM's turn/brake signal and then voltage at the bulb would be at zero between flashs from the new relays.
 

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Discussion Starter #8
You can "add" relays into the turn/brake wiring that would be fired by the BCM's turn/brake signal and then voltage at the bulb would be at zero between flashs from the new relays.
Thanks for the idea, but at this point I’m burnt out (pun intended) on the light bar. Got too many other projects on the list for the truck to get bogged down on one that was primarily aesthetic.
it just hacked me a little that it was advertised as plug & play and didn’t work that way.
But, I could add it to the bottom of the list if I can find the right relays.
 

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Discussion Starter #9
You can "add" relays into the turn/brake wiring that would be fired by the BCM's turn/brake signal and then voltage at the bulb would be at zero between flashs from the new relays.
Even though I returned the light bar I’ve been thinking about the relay idea. Not being good at electrical schematics and relays, I’m wondering if you had something specific in mind (like maybe a rough layout/schematic) or were just throwing an idea out.
I understand that the BCM signal would be used to energize the coil and close the contact In the relay. So the turn signal wire would go to relay coil and then to ground.
I’m assuming I would need a separate constant 12 volt power supply run to the back of the truck to one side of the contacts in each relay and a wire from the other side of the relay to the corresponding connection on the light bar . I’ll have to look at a relay to see which posts would be connected to which wire, but I might actually be able to do this.
 

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Discussion Starter #11
A relay is just a switch in a circuit to make it simple.
I think I finally wrapped my head around relays after reading "Relay 101 Basics for Auxiliary Loads" in the tutorials.
I believe using relays on the light bar will require a fused 12V power supply (that is "hot" when the ignition switch is on) run to the back of the truck (have to determine where to tap the power and how to route the wire). That wire would be connected to pin 87 on a relay for each turn signal and pin 30 on the relay would be connected to the turn signal wire on the light bar.
The turn signal wire from the trailer hitch harness would be connected to pin 86 on the appropriate relay for each side and pin 85 would go to ground. The turn signal "pulse" from the BCM would close and open the relay contact which should take voltage to the light bar back to zero (when the contact is opened). That should make the LEDs in the light bar work correctly (flash amber for turn/hazard). I'm planning on wiring up some relays to test the voltage output to see if I actually get 0 voltage between flashes.
Does that sound like it would work?
 

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Not sure how a relay would work with the flasher circuit. May not "switch" the relay slowly enough. Thinking a hyperflash would happen. Not sure though.
 

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Discussion Starter #13
I rigged a relay up on the trailer hitch wiring as I outlined by running the BCM flasher “pulse” on the left turn signal yellow wire to 85 and connecting 86 to to the white ground wire to close the contact when it flashes. I checked the relay operation with an meter and the voltage cut-off looked a lot sharper than the BCM “pulse“ voltage. For a trial, I connected the brown tail light lead (with the parking lights on to supply power) to 30 and connected 87 to one side of a light socket and the other side back to the white ground wire and got a sharp flash on an incandescent bulb.
I‘m going to contact the light bar supplier to see if he can loan one to me to test how the setup will work with the LED stris. If it works, I’ll run a 12 volt power supply to the rear of the truck, wire up a pair of relays and hook that sucker up.
 

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I was able to use a trio of relays(40 amp bosche relays) to intercept the right, left and stop signals from the bcm and the relays had enough resistance to prevent hiperblinking.

If you do not want to run all new wires clear back to the rear lights and the new relays, you could intercept the wiring at the front of the truck, place the relays up front and use the existing wires that go back to the rear lights as they currently exist.
 

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Discussion Starter #15
I already have 3157 LEDs in my rear turn signals (with resistors), brake lights and back-up lights so I don’t need relays in those positions. The LED light bar has a 4 pin connector that plugs into the trailer hitch but connected that way the amber turn signals and the hazard flashers on the light bar don’t work. I tried adding resistors to the light bar turn signal wiring but that didn’t work either. The light bar supplier says the voltage between flashes must go back to zero for the LEDs in the light bar to function properly and suggested changing to an electronic flasher. I can’t use an electronic flasher because our trucks don’t have flashers. The flash function is provided by the BCM. When you look at the flash “pulse” from the BCM on a meter it doesn’t appear to go completely back to zero voltage. By adding a relay as described, the voltage ”cut-off“ appears much sharper on the meter (doesn’t go all the way to zero but I think that is due to the time it takes the digital meter to react). Now I need to get a light bar to test. I sent the Christmas gift back when I couldn’t get it to work initially so I’ll either try to get the supplier to loan me one to test or buy it on Amazon and return it if the relays don’t do the trick.
You’re probably right that I could tap into the wiring up front to add the relays (and possibly/probably eliminate the resistors at the rear) but I need to confirm that the voltage from the relays will drive the LED light strips correctly and it’s easier at this point to do the trials at the rear of the truck.
 
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