Tapping wiring to activate brake lights remotely

tevake · 05-02-2016, 04:29 PM

This is a bit of a tech question, but I thought I'd run by friends here, before going to the tech thread.

I'm preparing to hit the road soon with my motorhome and will be towing the S C again.
The most awkward aspect of my towing setup is the temporary light bar and wire running over the car to the back of the coach to hook into the wiring there for brake lights to be activated by the coaches brake lights.

What I'd really like to do is to tap into the S Cs wiring at the front of the car that will allow the cars brake lights to be tied to the coaches brake lights. This is commonly done on other types of cars. But I'm not sure how to pull this off with the S C.

Any suggestions on how to do this ?

Cheers Richard

id10t · 05-02-2016, 04:42 PM

You would have to complete the circuit(s) the lights are on ... where is the actual switch located? By pedal cluster, activated by master cylinder or what? That would tell you where you need to have connection(s). Oh, and if you are doing brake lights you probably ought to do turn signals as well.

tevake · 05-02-2016, 05:18 PM

Yes, you are right. There is a seven pin connection with the coach that does operate the the turn signals also.

ossiblue · 05:48 PM

Just so you are aware, if not already, most states, including California, require a braking system in the towed vehicle if it exceeds a certain GVW--in Cal. it's 1500 lbs., though most other states it's 3000lbs. so the 911 wouldn't need it. These systems activate the towed vehicle's own brakes and brake lights because they simply apply the brakes via the pedal, just like a driver would. Turn and emergency lights are wired separately.

wdfifteen · wdfifteen's Garage

Quote:

Originally Posted by ossiblue

Just so you are aware, if not already, most states, including California, require a braking system in the towed vehicle if it exceeds a certain GVW--in Cal. it's 1500 lbs.

1500 lbs?? I was curious, as this sounds incredibly low. From the AAA website: "Every trailer coach or camp trailer with a GVW of 1,500 lbs. or more must be equipped with brakes on at least 2 wheels."
I went on to find:

ReadyBrakeâ„¢ Towed Vehicle Receiver Style Supplemental Brake System

I haven't flat-towed a car in years, and it looks like I won't be doing it ever again. Flat towing over any real distance is kind of sketchy to me anyway (wear and tear on the towed vehicle), strapping it on a trailer that has brakes makes a lot more sense.

RANDY P · RANDY P's Garage

Tap the +12V lead at the rear taillight (molex) that carries power only while the brake light is on, not when the parking lights are on. A T-tap and a male spade with 18GA wire should do it.

tapping that one lead with +12 will fire all the bulbs that are active when you hit the brakes. You just need to hit one bulb. Since this is a temporary setup, I'd route the wire in a way that is secure and removable. Just make sure you hit the right lead that only carries power while the brake lights are on.

It doesn't have to be pretty, just secure so it doesn't come loose while travelling.

tevake · 04:22 AM

I think the weight limit for towing W O brakes varies considerable from state to state.

That Ready brake mechanical system is interesting, haven't seen that before. I think that the sort of gear used most commonly in Europe.

Running wires from one end of the car to the other is what Im trying to get away from.
It's actually a cluster of wires to get what you want going at the rear. Guess they could be zip tied to the oil cooler lines as a route the length of the car. Any other thoughts on where to run the wires?

I did track down a Brake Buddy device on craigslist to use when I first started towing, but has not been working correctly. That now seems like the best course to take now in getting the lights working. Plus the brakes in the 911 also.
Funny I had just stashed it in the storage shed here where I am staying and forgotten about it.
Thanks Ossiblue for the reminder. I'll look into getting that repaired and back in action. Using that will get the brake lights and brakes going, I don't drive a lot at night usually, but can pull the parking lights on for night running.

That covers everything but the turn signals which would be good to have working also.
Wonder if they can be accessed at the front of the car?
I guess its clear, I'm not an electrical wizard.
So I really appreciate the suggestions.

Cheers Richard

wdfifteen · wdfifteen's Garage

I would not try to tie into the car's lights. I would mount a simple light bar on the car powered by the tow vehicle. Run the wires under the front lip of the hood, through the car, and out the engine compartment lid. Put a plug on it so it can be unplugged easily. It's way easier, the lights are higher, it includes tail and turn signal lights. Boom, done.

tevake · 05:20 AM

The light bar is what I ended up putting together on the day before setting out last summer. Once I realized the Brake Buddy was not working right. And The light bar does work nicely. Except for the cluster of wires taped over the top of the car.
I ran the wires thru a 3/8" clear plastic flexi hose to keep them all together. But it takes a lot of tape to keep this hose from blowing around and scuffing the paint.

Running this cluster of wires thru the interior of the car with plugs at each end would simplify that part of using the light bar, I just have not found a clean way to do that.

Even using the Brake Buddy, having this cluster of wires running from the coach to the back of the car and using the light bar, would simplify the lights issue. If I could find a good route through the interior.

Cheers Richard

id10t · 05-03-2016, 05:22 AM

Can you run your bundle of wires under the car instead of on top?

tevake · 05-03-2016, 05:36 AM

To this point I've had the wires run directly into the lights of the light bar making it one unit and requiring the wires to come off the car with the bar.
Adding a plug at the bar would let the wires just stay in place when the bar is removed.
This would allow the wires to be mounted semi long term and left in place.

I can't think of any clean way to run them under the car right now. Thru the interior makes sense if I can find a way thru the forward bulkhead and the firewall into the engine compartment. Don't really want to drill a bunch of holes in the car.
May have to do some digging around in the car today to see what access turns up.

I do see this as somewhat temporary, but would like to make it as simple as possible to get rigged up to tow. And then back to driving the car.

Cheers Richard

bkreigsr · 05-03-2016, 06:08 AM

......already been done
Donohue in the Penske Camaro - (Unfair Advantage ?)
Bill K

Mark Henry · 05-03-2016, 06:18 AM

Trailer wire kit, then mount an extra set of LED lights inside the cars tail lights.

RANDY P · RANDY P's Garage

racer tape it to the body. Or the light bar...

ossiblue · 06:49 AM

I'd have to check the wiring on an SC, but on earlier cars, the wires to the turn lights can be accessed via the fuse block. The power from the turn switch passes through the fuse, then to the front and rear turn lights. Additionally, the brake light switch on an SC is accessible in the trunk as well. Seems like you could run the wire bundle into the trunk, connect the R/L turn signal wires to the proper fuse terminal, and the brake light wire to the switch on the MC.

Your motor home, however, has a 7 wire plug which allows for a single wire for each of the turn signals/brake lights and another wire for the running lights. That means, your brake lights will also be the turn lights if your wire to your motorhome plug and you don't need to connect the turn lights separately. Again, running lights can be accessed through the fuse block. Do a search on the wiring diagram for your SC to find the proper fuse terminal for the running lights and turn lights.