I have a '86 K5 Blazer, and I'd like to know how to wire in a 3rd brake light. The problem is this. The turn signal and brake lights use the same circuit (one on left and one on right side). It would be nice to just wire in the 3rd brake light to the existing brake circuits, but it'll blink every time the blinker is turned on. So, how do you wire a 3rd brake light to only come on when the brake lights are on without blinking too. I'd assume a person could get fancy with a relay, but I can't figure that part out yet. I'd appreciate any suggestions.
CK5
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Is It Possible to Add a 3rd Brake Light to Square Body Truck???
- Thread starter PWagon
- Start date
If you connected the center light to both sides with diodes, it would always light steady whenever you're on the brake pedal. Unfortunately, it would flash if you have a blinker on and are not an the brake pedal. To get a brake only signal, I think you have to go to the cab of the truck. The flasher intercepts the brake signal and determines whether that side flashes or is steady. So from there or the brake switch you would need a relay (solid state would be ideal) to power the center light. It's also possible there is a trailer light controller that can do this kind of logic - like something to plug a 7-pin trailer into a 4-pin truck.
It seems to me the hardest part of the project is mounting the light, routing wire through the hardtop and adding another connector so the top can still come off. Or would this light be at the top of the tailgate? Still a lot of hassles with that.
It seems to me the hardest part of the project is mounting the light, routing wire through the hardtop and adding another connector so the top can still come off. Or would this light be at the top of the tailgate? Still a lot of hassles with that.
I've done this in variations, so Blue85 is dead on.
You have a few options:
1. Use the wiring at the brake pedal to get brake-only. I believe it's negative-switched, i.e. the one side is ground (purple/black?) and the other (black?) closes to ground when you press the pedal. You'd therefore run a constant fused hot lead to the + side of your brake light, then the - side would go to the brake pedal.
Pros: cheap, simple. Cons: Lots of extra wiring down the truck.
2. Do your own circuit to separate the turns from the brake. As mentioned, it can be done with a relay or two, though I recall the coil getting energized with turn signal so it would click every time you turned.
Pros: Cheap, less wiring. Cons: more complicated wiring, clicking would drive you batty. And wears out the relay(s).
3. Get a pre-made converter, e.g.
http://www.amazon.com/gp/product/B0046EKPHY/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
Pros: Simple, less wiring. Cons: Slightly more cost.
#3 was the winner for me. It does have a relay but it only clicks when the brakes are used.
-- A
You have a few options:
1. Use the wiring at the brake pedal to get brake-only. I believe it's negative-switched, i.e. the one side is ground (purple/black?) and the other (black?) closes to ground when you press the pedal. You'd therefore run a constant fused hot lead to the + side of your brake light, then the - side would go to the brake pedal.
Pros: cheap, simple. Cons: Lots of extra wiring down the truck.
2. Do your own circuit to separate the turns from the brake. As mentioned, it can be done with a relay or two, though I recall the coil getting energized with turn signal so it would click every time you turned.
Pros: Cheap, less wiring. Cons: more complicated wiring, clicking would drive you batty. And wears out the relay(s).
3. Get a pre-made converter, e.g.
http://www.amazon.com/gp/product/B0046EKPHY/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
Pros: Simple, less wiring. Cons: Slightly more cost.
#3 was the winner for me. It does have a relay but it only clicks when the brakes are used.
-- A
If you plan on using LED's for that third brake light, make sure you get an LED approved converter. Kert struggled with that one for awhile.
Though I didn't see if it was tagged as such, that one I linked to works on my solid state setup. The back bar is of course LED, and all the other bulbs have been replaced with LED's except the headlights.
rampage
3/4 ton status
And the 18 gazillion roof lights.
Shh. It's my one concession to the 80's. I wanted to do bright blue shock boots too but couldn't 'em to fit the Bilsteins, so had to make do with black
-- A
$21 sounds like a good deal - you don't have to figure out the diode/relay logic or how to package them. I would run it till the relay fails and if it had proved to be a good setup, upgrade it to a SSR then. I assume it works OK to use only the red output and leave the yellow and green disconnected. It should also work packaged in the rear of the truck.
You can still buy trailer light adapters for our trucks that plug and play into the rear tail-light harness. You would easily build one of the adapters linked above into one of those harnesses (on the bench) then swap it into the truck in like 1 minute. You could also take it out whenever you wanted and just plug the factory connectors back together. It could also be stacked with a second harness that would go to an actual trailer.
Just take a lead off the brake switch. From the brake switch it goes to the signal light switch in the column. The column switch disconnects the direction you want to indicate from the brake switch feed and connects it to the feed from the flasher. It also connects the front turn signal to the rear so they both flash.
When you pull the hazard switch it connects all the signals lights to the flasher. When you apply the brakes with the hazards on your front turn signals will also turn on with the rear brake lights.
Actually a pretty smart mechanism. It took 4 relays and a flasher for me to simulate the same function on a buggy I put turn signals into.
When you pull the hazard switch it connects all the signals lights to the flasher. When you apply the brakes with the hazards on your front turn signals will also turn on with the rear brake lights.
Actually a pretty smart mechanism. It took 4 relays and a flasher for me to simulate the same function on a buggy I put turn signals into.
