Brake light safety wire

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Brake light safety wire

Postby Modstock » Sat Nov 23, 2019 6:19 pm

I just finished tearing out a towbar wiring kit cause I had no brake lights.

Im pretty sure it was one of the diodes tied into the rear lights had went out.
Now I had a brake light safety wire hacked into the brake light switch.
Wasn't sure if I should eliminate that and wire back up the 2 wire's, so I clipped it off (orange tag wire).

My question is if I do electric brakes on my next trailer, is the brake controller going to be wired into this wire ???
99 jeep Cherokee.

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Re: Brake light safety wire

Postby Modstock » Sat Nov 23, 2019 6:32 pm

Here's the switch harness. Basically the 2 yellow butt connectors tie together to eliminate the red and black wire. Kinda screwed up, I know.

Damn hacks.

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Re: Brake light safety wire

Postby troubleScottie » Sat Nov 23, 2019 7:24 pm

The brake wire is part of the electric brakes. It provides the power to the brakes.

Assuming there is a break away switch which needs a battery ( the tow vehicle and trailer are separated, no power from the tow vehicle), the auxiliary power and ground are needed to charge the break away battery. The break away switch activates the electric brakes. Which of course means extra routing from the TV to the brakes.



Diode are generally there to allow 2 power sources to power something without the rest of the system being powered and prevent flow of power in an inappropriate direction. Like you have a switch to turn on the reverse light in addition to the TV reverse switch/wire.

Not sure why there would be diodes if there is no other switches. Thinking outside the box, the brake away switch could have used the diodes. A bit over the top but would work. Remember, the break away switch is only active when the TV is removed. No real need to protect the TV brake circuit.
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Re: Brake light safety wire

Postby Modstock » Sat Nov 23, 2019 8:01 pm

So I could eliminate the red and black wire (brake safety wire) and go back to OEM wiring just before the switch ?

I'll have to look into a brake controller in the future . Not sure what goes into wiring one of those up.

((Update))
Found out why my rear park lights didn't work.
Someone put a add a fuse on my LR park light fuse . Probably for towbar harness.
Had 2 fuses, which one was burned out.
I eliminated that, put the good fuse in and now have rear park lights.
Still no brake lights coming on, I suspect the brake light switch is toast.

Geeze, all this crap to tow bar a jeep behind a motorhome. Better just to trailer it.

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Re: Brake light safety wire

Postby Modstock » Sun Nov 24, 2019 2:28 pm

Today I picked up a new brake light switch. Still nothing.
But now when I turn the park lights on the brake lights are stuck on, even with the switch disconnected.

I was told maybe my trailer harness could be hurt somehow.
It's a T-harness and one of the converters could be fried ?

I'll unplug that and see if there's any difference.
Any Cherokee owners in here ???


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Re: Brake light safety wire

Postby troubleScottie » Sun Nov 24, 2019 4:30 pm

Pulling/towing a vehicle uses a different wiring scheme than a trailer.

Given the parts you are referencing and the comment on the tow bar -- this is a hardware diode kit. These are NOT inter-changable with a 4 to 7 pin towing system. It would appear you need to rewire.

For a trailer:
typical 4 to 7 pins
ground
running lights
left turn-stop
right turn-stop
power
reverse
brake

For towing a vehicle, there are several solutions:

Lifted from etrailer https://www.etrailer.com/faq-wiring-kits-for-vehicles-being-towed.aspx#diode

To legally flat tow your vehicle you must ensure that it is properly wired and connected to your RV. Your towed vehicle's signal lights must act in accordance with the brake and turn signal lights on your RV or tow vehicle. There are four basic ways that you can achieve this:

(1)Removable tail light kit
Bypasses towed car's electrical system
Easily mounts and removes for occasional towing
(2)Bulb and socket kit
Bypasses towed car's electrical system
Permanent solution for frequent towing
(3) Hardwire diode kit
Splices into towed car's wiring
Permanent solution for frequent towing
(4) Custom-fit, plug-in wiring harness
Plugs into towed car's wiring
Permanent solution for frequent towing


Hardwire Diode Kits
Diode Wiring Kit

The traditional method of wiring your towed vehicle to ensure that its signal lights will act in accordance with your RV's lights while it is being towed, is to use a diode kit. This method requires a more involved installation process, but once complete you never have to re-mount, set up or manually activate a thing.

Hardwire diode kits can include:

4 Diodes for 2-wire systems (or for a 3-wire towed car that you intend to wire as a combined system)
6 Diodes for 3-wire systems
Single block-style diode for either 2-wire or 3-wire systems


Kits that include either four or six diodes that splice into your towed car's wiring are the most common tail light wiring kits.

(addition information in the link)
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Re: Brake light safety wire

Postby Modstock » Sun Nov 24, 2019 10:48 pm

When I bought the jeep it came with the tow bar and harness already installed. I dont even use it. Which all of it is now removed.

GOOD NEWS THOUGH.

I was able to get it fixed today.
Turns out I had no power to the brake switch itself.
Checked all my fuses inside but there was 6 (NOT labeled) fuses in the power distribution box in the engine bay.
Couldn't find out what those are even with owners manual, Haynes manual, internet.
Tested those and 1 was burnt out. Replaced it and now have power to the switch.
Also had to replace the Left marker light fuse again.

Now here's the main issue.
The wires going into the rear hatch were starting to break causing the short.
These operate the rear wiper, 3rd brake light, license plate light, defroster , door lock.
13 wire's through a 1/2" hole. Seriously.
I'll be fixing the wires and send ONLY the 3rd brake wires through that hole and re-route the others so there is no more issue down the road.

Everything is back to stock now.

Maybe later this week I'll test the trailer T-harness to see if it's still good.

Out of the 13 wires going through that small hole. 6 were broken. ImageImage

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Re: Brake light safety wire

Postby Socal Tom » Sun Nov 24, 2019 11:21 pm

Modstock wrote:So I could eliminate the red and black wire (brake safety wire) and go back to OEM wiring just before the switch ?

I'll have to look into a brake controller in the future . Not sure what goes into wiring one of those up.

((Update))
Found out why my rear park lights didn't work.
Someone put a add a fuse on my LR park light fuse . Probably for towbar harness.
Had 2 fuses, which one was burned out.
I eliminated that, put the good fuse in and now have rear park lights.
Still no brake lights coming on, I suspect the brake light switch is toast.

Geeze, all this crap to tow bar a jeep behind a motorhome. Better just to trailer it.

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I ended up buying a set of magnetic tow lights, like these
https://www.walmart.com/ip/MaxxHaul-80778-12V-Magnetic-Towing-Light-Kit-Dual-Sided-for-RV-Boat-Trailer-and-More-DOT-Approved/357416250?wmlspartner=wlpa&selectedSellerId=0&adid=22222222227136718474&wl0=&wl1=g&wl2=c&wl3=245592341456&wl4=aud-834279576126:pla-402868913414&wl5=9061192&wl6=&wl7=&wl8=&wl9=pla&wl10=8175035&wl11=online&wl12=357416250&veh=sem&gclid=CjwKCAiA8ejuBRAaEiwAn-iJ3iZzY97xuG_7PhfNfnOVurDQa5IlmOdDPu-dBQjsZUrCC8YNdEAkEBoC2vcQAvD_BwE

It was much better.
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Re: Brake light safety wire

Postby Modstock » Mon Nov 25, 2019 8:29 am

Yes. If I ever had to use the tow bar, this is what I'd do. Much simpler.

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Re: Brake light safety wire

Postby Modstock » Sat Nov 30, 2019 10:45 pm

Good news. My trailer T-harness is fine. Eleven wires were relocated and the 3rd brake light is now working
All is good and can tow the teardrop again.

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