Now for the difficult part: Tail Lights.

Tail lights are difficult for several reasons. Isolating the circuit from feedback using a diode will require splicing or running new wires to several locations.
Typically installing a diode at one rear light fixture will only power 1 light. There are some options to operate both lights.
You can rewire the rear light from the other side and splice in to that diode, or you can use 2 diodes.
The next issue is the license plate light. By law you are required to have a working license plate light.
Most technicians do not wire the license plate light. Remco does not include directions in their lighting kit nor does any other company that I’m aware of.
I have talked to Remco’s installers and they do not wire that circuit.
The only way to make that license plate light work correctly is to cut the original feed to the socket and run a new wire to the location of the diode.
I usually install the tail light diode on the driver’s side. Remove the tail light fixture.
Cut the wire feeding the right tail light. Cut the wire feeding the license plate light. Insulate both ends that fed the original circuits with electrical tape or a connector.
I like to use a butt connector and dielectric grease so the wire and circuit will still be in good condition is ever reused.
Attach equal size wire to the bulb side of each light. Run the new wires to the driver’s side tail light.
You can use a terminal that will splice 3 wires together. I usually use a yellow female spade terminal. The spade will attach to the diode.
Yellow is for 10 gauge wire which should accommodate the 3 small wires.  Cut the original wire feeding the taillight bulb on the driver’s side.
Install a terminal to the harness side of the wire and attach it to the input side of the diode.
Install a terminal on the brown wire from the trailer wire harness you installed and attach it to the other input side of the diode.
Install the yellow spade terminal to the wire feeding the left tail light bulb, and the 2 wires you routed to the bulb area.
Attach this terminal to the output side of the diode. This will power all 3 lights from either the vehicles harness or the trailer harness you installed.

You can now install the front trailer connector. Pull the excess wire through the trailer connector. Leave a few inches of extra wire. Install the wires to the connector.
If using a round 4 wire connector there is no standard wiring pattern.
I use this type connector with a coiled cord if towing with lights only (no lube pump, braking unit or charging system).
You will probably need to install a mating 4 wire round connector to your RV. You can simply match your wires to each since there is no industry standard.
If you have a lube pump you will be using the 6 wire connectors and coiled cord supplied from Remco. Their wiring schematic is in the instructions.
If you need additional wires, I recommend using a 7 way connection. 7 wire harnesses can be purchased from an auto parts supplier.
You will need to cut it to the proper length to run between the RV and towed vehicle, then attach the connectors to it.
I usually tie strap the cord to the tow bar, then simply disconnect the end from the towed vehicle when not in use. If you need more than 7 wires, use 2 – 4 wire coiled cables and sockets.

Caution: I recommend not connecting your harness between the RV and towed vehicle until you are finished connecting your tow bar and have turned off the vehicle and all of its lights. In some vehicles the light circuits pass through one of the computers and it may be possible to damage this circuit if there are 2 inputs at the same time.

A light bar can be used if towing for a limited number of times. There is little labor and time involved in set up.
Since most RV’s have a wiring connector already in place, you can simply run an extension along the tow bar and back to the lights.
A magnetic mount is generally used to attach the lights to the vehicle. Storing a light bar, installing and removing a light bar become tiresome if towing frequently.
Wires dangling down and difficulty securing them is another good reason to hard wire the towed vehicle’s rear lights.
There are now wireless tow lights available. I have not tried a wireless light set up, so I will not comment on them at this time.

Most often the rear lights on the towed vehicle are hard wired to work off the RV. Wiring kits are available from most tow bar manufacturers.
These kits include wiring, connectors, and diodes. The diodes are necessary to avoid electrical feedback through the towed vehicles electrical system.
Due to the design of the automotive electrical system, a turn signal switch or a brake light can feedback through a vehicle possibly damaging the system or running an unwanted circuit.
A diode simply isolates the current flow to the direction of the light and not in reverse.
The diodes designed for towing should be used since they are designed for exterior use and typically have a heat sink built on the diode.

Hard wiring tow lights can be very complicated and difficult. In some applications, separate light bulbs may be needed.
Vehicles that use ground switching to activate lights will require separate bulbs.
Separate bulbs can create problems since there is usually not enough room for another socket and bulb.
Be sure to check your rear brake lights for voltage before deciding on which towed light system to use.
Tow vehicles use positive switching to activate the towed vehicle lights and cannot activate negative switching lights.
In other words, a vehicle that uses ground switching has positive power at the rear light when the light is off and uses ground continuity to activate the light.
You can test for ground switching with a simple voltage test at the rear lights. I have found a couple of vehicles that use ground switching for brake lights, but not running lights.
Remove the rear light fixture and test for constant voltage at the positive feed for the brake light. If it has constant voltage with the light off, it is ground switching.
If it gets voltage only when applying the brake, it uses positive switching. It is important that you understand you will be using the red brake lights.
I do not recommend using amber turn signals for towing. Some RV’s have rear amber lights.
They do not typically use an amber circuit for towing, but rather a converter for red light only use.
You can have an RV with amber turn signals and still use the red brake lights only for both brakes lights and turn signal lights on your towed vehicle.

I make my own wiring kits. I use bulk wiring and have a bulk supply of diodes. Roadmaster sells their diodes in bulk bags and they are very good quality.
Using a bulk roll of wire eliminates the problem of the wiring being too short. I find that Remco supplies a harness that is too short for almost all vehicles.
Most auto parts stores have 4 wire trailer wire in bulk. Generally I would buy about 30 feet to be sure you have enough. You don’t want to splice the harness.
I usually run my wiring outside the vehicle. It is easiest to run the harness back while the front fascia or bumper is off during base plate installation.
Find a good location for the light socket. One of the reasons I like Blue Ox base plates is because they provide a mounting point for the socket.
You can use any type trailer socket you’d like. I usually figure how many wires in total I will be running before choosing a socket.
There will be 4 wires for lights. If using a lube pump, there will be 2 more. If using a braking unit there may be more, and if using a battery charging system, there will be more.
I will cover charging systems and braking systems in another article.
Mount your socket, but do not connect any wires yet. Start to run your 4 wire harness to the rear. Lead the harness into the engine compartment.
I usually go to the driver’s side. Stop at an area at the front where you can attach the ground wire to a good ground source.
I look for a factory harness ground point. Split the white wire off from the 4 wire harness and cut to length. Install a terminal then attach at ground point.
Continue to run the remaining 3 wires to the rear going down near the firewall then to the under side of the vehicle.
There are usually brake lines and/or fuel lines to secure the harness to.  Be careful to avoid sharp or rotating objects and areas that will get hot. Support harness with tie straps.
When getting near the rear decide how the harness will reach the lights. Remove the rear light fixtures to see how the factory harness runs to them.
If there is outside access to the factory harness, run the 4 wire harness directly to that area.
If the factory harness is inside the vehicle, you will need to find an easy access point to run the harness through.
Typically I find trucks and sport utility vehicles have outside harnesses and cars have inside harnesses.
I look for a factory grommet or vent flap to run the wire to the inside for cars. Be sure to poke a small hole and seal it with silicone seal.
Split the green wire off from the 4 wire and run it to the right side rear light. Run the other 2 wires to the left side rear light.
Using only the red brake light (not amber), find the factories wire that feeds the left brake light. Be sure to test for voltage right next to the light bulb while someone applies the brake.
Some vehicles use “bulb out” indicators. You will need to be on the bulb side of the indicators.
Cutting the brake light wire very close to the bulb/socket will ensure you are on the correct side of a bulb out indicator.
Cut the wire; install the terminal connector provided with the diode to both ends of the cut wire.
Be sure to use dielectric terminal grease to all terminals and connections. Poor or corroded connections are the number 1 problem I see with tow lights.
Connect the wire coming from the vehicles harness (feeding the light) to a diode input using the diagram on the diode for proper electrical flow.
Run the yellow from the new harness to the other diode input. Install a terminal on the cut wire (bulb side) and connect to output diode terminal.
Follow the same procedure on the right rear red light using the green wire from the 4 wire harness.

An air cylinder is used inside the towed vehicle to push the brake pedal.
The cylinder mounts to the floor or seat by a bracket and quick connecting pin.
In my opinion Roadmaster has an advantage here since they now have brackets available to bolt directly
on the driver’s seat for some vehicles. (With a seat bracket, it is not necessary to drill holes in the floor).
A rod attaches to the brake pedal using a spring loaded clasp.
An air line is routed from the front of the towed vehicle along the under hood area, then inside the vehicle
going through the firewall. A connector and bracket are provided to mount at the front of the towed vehicle
close to the tail light wiring connector. The line attaches to the air cylinder by an air coupling.
It should be routed along the sill plate to an area under the seat where it can be stored out of site when not in use.

On the coach end, the air supply will be teed into the air brakes. Be certain the coach can handle this system.
I recommend checking with the manufacturer of the coach to be sure they will allow tapping into the air brake system.
If allowed, hook into the air brakes near the rear of the coach close to one of the actuators at the relay.
The actuators are the air bellows that activate the braking mechanism.
I find in most applications there is a relay close by that has a plug in it.
Be sure the wear some type of hearing protection for the next step.
Simply remove the plug then have a helper activate the brake by pressing the brake pedal.
Be sure the air flow comes out of the fitting where the plug was removed only when the brake pedal is activated.
Use one of the adapters provided to connect an air line to the correct fitting.
In some cases you may need to find the correct style or size fitting from a parts supplier.
Route the air line away from any moving parts to the rear of the RV where a bracket and coupler can be mounted.
A coiled air hose is provided to make the connections between vehicles.

There is an optional indicator light provided to mount inside the RV.
The light is activated from the towed vehicle’s brake light switch when the brake is applied.
A single wire is provided with the kit and will need to be routed from the brake light switch to the front of the towed vehicle.
You will need to install a brake light relay kit. This kit will eliminate two problems.
It will disable the towed vehicle from lighting the brake lights thus eliminating a battery run down condition.
It will also keep the braking unit from overriding the turn signals while towing.
The relay kit is available from Roadmaster and included with Blue Ox’s BrakeMaster.
There is a separate wire with quick connectors to attach between the towed vehicle and RV.
A wire will need to be routed from the rear of the RV all the way to the front, then inside to the dash area.
A hole can be drilled to install the light.

A breakaway unit is separate for both braking units and is required by law in some areas.
Unfortunately, the breakaway makes a very simple and easy to install braking unit difficult and complicated.
In my experience the breakaways take about as much time to install as the rest of the system.
The breakaway uses a separate air storage cylinder to supply air to the braking unit in case of a separation from the RV.
There is the typical 2 wire breakaway electrical switch to mount at the front of the towed vehicle.
This switch will be linked to the RV with a small lanyard cable.
You will need to find a location under hood for a rather large air supply tank.
The tank will tee into the air supply line feeding the inside cylinder.
There is a solenoid assembly that activates the breakaway from the breakaway switch.
There is tee to feed the inside cylinder from the solenoid.

This type of air braking systems is what I recommend for RV’s with full air brakes
as long as the manufacturer of the RV permits tapping into the air brakes.
They work proportionately from the RV’s brakes without electronics which makes them very accurate, reliable, and dependable.
Preparing to tow is quick and easy. The only problems I have seen with this system have been with the breakaway.
The air operated breakaway system is reliable with the exception of the breakaway switch which I explained in a previous article.

There are many things to think about when deciding what vehicle to tow behind an RV. Using an existing vehicle, finding an ideal tow vehicle, weight, braking, ease of use, and costs involved are all things to consider.
In general, a vehicles transmission or transaxle must either be disabled or lubricated to tow it. There are several methods available to perform this function.

Tow Dolly
I refer to towing a vehicle with all 4 wheels on the ground as “4 wheels down”
I will start with tow dollies. A tow dolly is a 2 wheel device with a platform and ramps that attaches
to your RV’s tow hitch. A dolly requires attachment to your RV, driving your tow vehicle up the ramps
to the platform, latching the dolly so the ramps are in a locked position, and strapping the tires to secure
the vehicle to the dolly.

I consider towing any vehicle backwards on a dolly dangerous and do not recommend it therefore;
a rear wheel drive vehicle would require additional equipment to be towed forward on a dolly.
There are several varieties and a number of dolly manufacturers. A basic dolly has fixed platforms.
Upgraded models have swivel platforms, and top of the line models have wheels that turn.
I recommend either swivel plates or turning wheels because when turning while towing, the front wheels
on the towed vehicle will try to turn even though they are strapped to the dolly. If the platforms or
wheels on the dolly do not move (fixed platform) the towed vehicle wheels will bind causing
the hold down straps to loosen or the vehicle to shift on the platforms. Many vehicles can be towed
using a dolly. In general front wheel drive works best and you must have a vehicle that is not too
wide to fit the dolly.
In my opinion, a dolly works well for someone who wishes to tow more than 1 vehicle
since the towed vehicle does not require any additional items to be towed.

Options for dollies include a folding feature to make them more compact for storage and brakes.
Brakes should be considered and may be required by law. Towing laws vary by state and
your state laws should be checked prior to purchasing. Be sure to purchase your dolly
with brakes if required by law since brakes are difficult and expensive to add later.
There are many reasons a dolly is not the preferred method.
Dollies do not tow as well as a vehicle with 4 wheels down.
Dollies are a hassle to park and deal with at campgrounds. Dollies take longer and more work
to load and unload than connecting/disconnecting a 4 wheels down vehicle.
Hold down devices (straps) are a constant worry.

To tow your vehicle, you will need a tow bar, base plates, some type of rear lights and most likely a braking system.
There are a variety of tow bars and base plates on the market.
We deal with Blue Ox, Demco, and Roadmaster. My favorite is Blue Ox.
I