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Full Version: Flat towing. How to wire tail lights?
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JRust
Have any of you wired your tail lights to work for flat towing? Id like to get this hard wired so it's always ready for an easy plug in. Also not needing to use the magnetic lights anymore. So wiring for your typical flat 4 plug in.

What say you smart wiring guys confused24.gif
Mike Bellis
It can be done but this issue is the tow vehicle and standard 4 wire trailer plugs. Amerikan cars use the brake light as the turn signal. Left and right lamps wired independently

The 914 has a common brake light circuit and independent turn signals.

So to make it work, you will need to run 3 wires to the tail lamps of the 914 and rewire the brake lights to include two diodes where the circuit splits right and left. You will also need diodes on the new trailer wires to each brake light to prevent feedback from right to left. The parking light/running light wire should also have a diode added to the 914 circuit unless you want all the vehicle lamps lighting up at night.

Here is a basic wiring diagram
Click to view attachment
Mike Bellis
I should also mention that your 914 brake lights will now be turn signals while towing and should work normal while driving.
914itis
I wired mine on the hazard wire from my tow vehicle to the rear / front yelow lights of the 914. I just keep my hazard on. I also have a battery disconnect switch to kill all power on the 914.

I will post some pics soon .
Krieger
agree.gif
I did the kit from Roadmaster. I have the plug taped under the front spoiler to my car. I used it for 5 long trips with no problems.
Elliot Cannon
Don't tow it. DRIVE it. driving.gif biggrin.gif (carefully)
jcd914
I went the simple route and just tied into the 2 turn signal wires and running light wires in the front trunk. No diodes or relays or wiring kits, just about 4 feet of trailer wiring harness and a few scotch lock and spade connectors.
Since on my tow vehicles the two turn signals function as the brake lights, this provided both turn signals and brake lights on the 914.
I did have to put the connectors in the wiring so I could separate the front turn signals because they were too much for the flasher in the tow vehicles.
The added advantage I got was the front parking and clearance lights were also lit up while towing.

Jim
JRust
QUOTE(jcd914 @ Sep 12 2015, 02:19 PM) *

I went the simple route and just tied into the 2 turn signal wires and running light wires in the front trunk. No diodes or relays or wiring kits, just about 4 feet of trailer wiring harness and a few scotch lock and spade connectors.
Since on my tow vehicles the two turn signals function as the brake lights, this provided both turn signals and brake lights on the 914.
I did have to put the connectors in the wiring so I could separate the front turn signals because they were too much for the flasher in the tow vehicles.
The added advantage I got was the front parking and clearance lights were also lit up while towing.

Jim

So basically you unplug your front turn signals? Use 2 wires off them to run your lights in back? Otherwise your front turn signals with everything was to much pull for your tow rig? Am I understanding that right?
Spoke
QUOTE(JRust @ Sep 13 2015, 01:30 AM) *

QUOTE(jcd914 @ Sep 12 2015, 02:19 PM) *

I went the simple route and just tied into the 2 turn signal wires and running light wires in the front trunk. No diodes or relays or wiring kits, just about 4 feet of trailer wiring harness and a few scotch lock and spade connectors.
Since on my tow vehicles the two turn signals function as the brake lights, this provided both turn signals and brake lights on the 914.
I did have to put the connectors in the wiring so I could separate the front turn signals because they were too much for the flasher in the tow vehicles.
The added advantage I got was the front parking and clearance lights were also lit up while towing.

Jim

So basically you unplug your front turn signals? Use 2 wires off them to run your lights in back? Otherwise your front turn signals with everything was to much pull for your tow rig? Am I understanding that right?


I think you are correct in your assessment. There are a few caveats though:

If you run any type of LED turnsignals front or rear likely you wouldn't have to remove the front lights.

This will only function correctly if you have US lenses in the rear as when on brakes the rear lights need to be red. Euro lenses with amber turnsignal lenses would be amber for brakes.

One interesting point with this setup is if you have US rear lenses, you could replace the front turnsignal lights with a wired bulb base like I use on my LED boards. This way you would not have to touch the wiring of the 914.
jcd914
QUOTE(Spoke @ Sep 13 2015, 05:14 AM) *

QUOTE(JRust @ Sep 13 2015, 01:30 AM) *

QUOTE(jcd914 @ Sep 12 2015, 02:19 PM) *

I went the simple route and just tied into the 2 turn signal wires and running light wires in the front trunk. No diodes or relays or wiring kits, just about 4 feet of trailer wiring harness and a few scotch lock and spade connectors.
Since on my tow vehicles the two turn signals function as the brake lights, this provided both turn signals and brake lights on the 914.
I did have to put the connectors in the wiring so I could separate the front turn signals because they were too much for the flasher in the tow vehicles.
The added advantage I got was the front parking and clearance lights were also lit up while towing.

Jim

So basically you unplug your front turn signals? Use 2 wires off them to run your lights in back? Otherwise your front turn signals with everything was to much pull for your tow rig? Am I understanding that right?


I think you are correct in your assessment. There are a few caveats though:

If you run any type of LED turnsignals front or rear likely you wouldn't have to remove the front lights.

This will only function correctly if you have US lenses in the rear as when on brakes the rear lights need to be red. Euro lenses with amber turnsignal lenses would be amber for brakes.

One interesting point with this setup is if you have US rear lenses, you could replace the front turnsignal lights with a wired bulb base like I use on my LED boards. This way you would not have to touch the wiring of the 914.


Yes I cut the wires going to the front turn signals and put in male/female spade connectors. I then just unplugged them and plugged in the trailer harness. The running lights I used a scotch lock connector that allows for a male spade to be plugged in and just used those to connect the trailer harness to the running lights. This was done in the front driver side corner of the front trunk.

Spoke is correct in that you should have US spec rear lens so the brake lights are red. I was using Euro lens so my brake lights were not red and not legal but I never got stopped for them.

Jim
JRust
Nice I've got US rear lenses so no problem there. Thanks Jim that is a pretty easy setup. Do you remember which color wire does what?
Mike Bellis
QUOTE(JRust @ Sep 13 2015, 02:00 PM) *

Nice I've got US rear lenses so no problem there. Thanks Jim that is a pretty easy setup. Do you remember which color wire does what?

You need to realize that connecting this way does not give you a bright brake light. It lights up the parking lights as turn and brake and does not provide a dimmer parking light for night towing.
forrestkhaag
I'm going to stay with magnets.. bright turns, brake lights, clean, easy to install, always working turn signals, brake lights, etc. which CHP wants clear documentation on in case of an accident,... and no futzing with in-house wiring compromising your in-house wiring.

I am towing the car to another spot on the globe tomorrow am and it is an easy hook up in 10-15 minutes /

I like the input from all and the various options and detail......... but the Devil is in the details........ beerchug.gif
Spoke
QUOTE(Mike Bellis @ Sep 13 2015, 05:14 PM) *

You need to realize that connecting this way does not give you a bright brake light. It lights up the parking lights as turn and brake and does not provide a dimmer parking light for night towing.


Not sure what the issue is.

Green wire would go to the right high power filament for RT turn and brake.
Yellow wire would go to the left high power filament for LT turn and brake.
Brown wire would go to both L and R low power filament for running lights.
White wire would go to the body of the bulb base on both sides for ground.

The brake and turnsignal would be bright for both sides. Did I miss something?
JRust
QUOTE(Mike Bellis @ Sep 13 2015, 02:14 PM) *

QUOTE(JRust @ Sep 13 2015, 02:00 PM) *

Nice I've got US rear lenses so no problem there. Thanks Jim that is a pretty easy setup. Do you remember which color wire does what?

You need to realize that connecting this way does not give you a bright brake light. It lights up the parking lights as turn and brake and does not provide a dimmer parking light for night towing.

Ah! That makes sense. While that would be much easier to wire. I don't think I will go that way. I have been using the magnetic's for quite a while. I've got multiple set's so this isn't a priority at this point. That will go on my list for wiring to the back & adding the diode's to make it work right.
Mike Bellis
QUOTE(Spoke @ Sep 13 2015, 04:58 PM) *

QUOTE(Mike Bellis @ Sep 13 2015, 05:14 PM) *

You need to realize that connecting this way does not give you a bright brake light. It lights up the parking lights as turn and brake and does not provide a dimmer parking light for night towing.


Not sure what the issue is.

Green wire would go to the right high power filament for RT turn and brake.
Yellow wire would go to the left high power filament for LT turn and brake.
Brown wire would go to both L and R low power filament for running lights.
White wire would go to the body of the bulb base on both sides for ground.

The brake and turnsignal would be bright for both sides. Did I miss something?

Connecting to the front of the 914 does not light up the 914 brake light. It only lights up the turn signal lamp and running. In many cases, this is a lower wattage and does not produce a brighter red as the brake light. When I am the driver following, I want to see a brake light, more intense, not just another lamp illuminate. It makes for a safer trip while towing to have a bright brake lamp.

Do what you guys want. I don't really care. For mine I will be lighting up the correct lamps on the 914. I already have extra wires to the rear of the car, so with a few diodes it's easy. Plus my solution is semi permanent and it only a matter of plugging in the trailer connector to the tow vehicle.


Just because it works doesn't make it right...
Spoke
QUOTE(Mike Bellis @ Sep 13 2015, 09:42 PM) *

Just because it works doesn't make it right...


Ouch. I wasn't right, I was incorrect. I was thinking of how I configured my LED turnsignals where I light up the LED array gently on running lights and brightly on turnsignal.
jcd914
QUOTE(Mike Bellis @ Sep 13 2015, 06:42 PM) *

QUOTE(Spoke @ Sep 13 2015, 04:58 PM) *

QUOTE(Mike Bellis @ Sep 13 2015, 05:14 PM) *

You need to realize that connecting this way does not give you a bright brake light. It lights up the parking lights as turn and brake and does not provide a dimmer parking light for night towing.


Not sure what the issue is.

Green wire would go to the right high power filament for RT turn and brake.
Yellow wire would go to the left high power filament for LT turn and brake.
Brown wire would go to both L and R low power filament for running lights.
White wire would go to the body of the bulb base on both sides for ground.

The brake and turnsignal would be bright for both sides. Did I miss something?

Connecting to the front of the 914 does not light up the 914 brake light. It only lights up the turn signal lamp and running. In many cases, this is a lower wattage and does not produce a brighter red as the brake light. When I am the driver following, I want to see a brake light, more intense, not just another lamp illuminate. It makes for a safer trip while towing to have a bright brake lamp.

Do what you guys want. I don't really care. For mine I will be lighting up the correct lamps on the 914. I already have extra wires to the rear of the car, so with a few diodes it's easy. Plus my solution is semi permanent and it only a matter of plugging in the trailer connector to the tow vehicle.


Just because it works doesn't make it right...


Mike's method is a very good way to do this, very elegant.

But since both the 914 brake light bulb and turn signal bulb are 21 watt bulbs there will be no significant difference in the brightness.

Jim
Spoke
QUOTE(jcd914 @ Sep 15 2015, 02:21 AM) *

But since both the 914 brake light bulb and turn signal bulb are 21 watt bulbs there will be no significant difference in the brightness.

Jim


The 914 brake light bulb is dual filament; 21W brake light + 5W running light.

Agreed turnsignal bulbs are 21W single filament.

The 5W brake bulb lights when the running lights are on.
The 21W turnsignal is on only for turnsignal and brake.

Running lights are dim, turnsignals+brakes are bright. Is this not so?
AZ914
QUOTE(Spoke @ Sep 15 2015, 07:19 AM) *


The 914 brake light bulb is dual filament; 21W brake light + 5W running light.

Agreed turnsignal bulbs are 21W single filament.

The 5W brake bulb lights when the running lights are on.
The 21W turnsignal is on only for turnsignal and brake.

Running lights are dim, turnsignals+brakes are bright. Is this not so?


Yes.. you can just use the running/brake light as the combined running/brake/turn light. The link I provided earlier to eTrailer shows the wiring configurations.
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