Tail Light Converters
Understanding the problem:
The tail lights of a tractor are wired as Stop/Turn lights. In other words, a tail light has one wire for the Stop and Turn function and one wire for the tail light/running light function and a Ground wire.
On a Volvo, the is the wiring running along the right frame member.
The commercial trailer plug is wired for separate Stop and Turn lights. In other words there are separate Stop lights and Turn lights with the Running lights often in the Stop lights and sometimes in the Turn lights.
On a Volvo, this is the wiring running along the left frame member.
Now an RV trailer is wired as Stop/Turn and yet the most apparent place to wire the trailer cable plug is from the truck trailer receptacle. That is the issue.
Now a simple solution could be to wire the RV trailer receptacle to the truck tail light wiring and wire the truck bed to the truck trailer receptacle wiring. But there are some reasons not to do that, like isolation of truck and trailer wiring, that the decision is to use the truck trailer receptacle wiring and to use a converter to combine separate Stop and Turn signals into Stop/Turn signals. That is what is converted in this section.
Tail Light Converters:
Converters are typically solid-state devices that combine the Stop and Turn signals into Stop/Turn signals. Since the converters are self powered they also isolates the trailer light signals from the tow vehicle so you don't have to worry about overloading the circuits on the tow vehicle.
The more widely used converter is the Hoppy 46255. Several people have Reported having Problems with the 46255 over time so I opted to go with the Hoppy 46365 which also offers 8 Amps of power. If you plan on having more than the average number of lights on your 5th-Wheel this is an added bonus. Several members have chosen to go with the Hidden Hitch Powerline converters which are available in 5 to 20 Amp versions.
|From Mark & Dale Bruss (Mark):
If you choose to use Hoppy converters, do not plan on buying one at a local store. The Hoppys available at U-Haul, etc. are usually the lower end non-powered models and are very poor for the HDT application.
The Jackalopee Converter
A recent entry in the tail light converter market is the Jackalopee Converter from Henry Szmyt. The Jackalopee is a self-contained in a waterproof box that can be mounted near the hitch and plugged into the truck trailer receptacle and has the RV trailer receptacle attached. While the Jackalopee is similar to the four relay schematic following, the Jackalopee fully isolates the truck wiring and is fully assembled and ready to go.
|From Mark & Dale Bruss (Mark):
When I first saw the relay based converters I was concerned about mechanical wear. Reviewing the Volvo Schematics, I realized that all the turn and tail light functions on the Volvo are run through relays, so that is not an issue.
If you prefer, you can make your own DIY Tail Light Converter by utilizing either three or four 40 Amp Bosch style relays as displayed in the two schematics below that were designed and drawn by fppf.
Like the Hoppy and Hidden Hitch self powered tail light converters, the DIY self powered three relay tail light converter shown below will isolate your 5th-Wheel's lighting from your trucks OEM electrical system which will eliminate any possibility of screwing up your trucks electrical system.
On the other hand, the four relay version shown below isn't self powered therefore I personally would shy away from the four relay version unless you want to Risk the Chance of Screwing Something Up in your trucks electrical system.
|Three Relay Version||Four Relay Version|
Mid Year 2004 and newer Volvo's will have to use this method or another similar method as the Hoppy and Hidden Hitch type tail light converters will not work on newer Volvo's as the newer Volvo's have a computer (LCM = Light Control Module) that controls the lighting which will in turn cause a conflict with any commercially available tail light converters.
If you plan to pick up 12 Volt power from the center auxiliary pin in the OEM trailer electrical socket located behind the cab to feed power to a DIY powered TL converter or the Jackalopee, Make Sure there is a 40 Amp fuse in - location B2 - which is marked "Trailer AUX" in the secondary fuse panel that is located directly behind a small panel under the drink holder on the dash.
Access to the secondary fuse panel is achieved by removing two screws that are hidden directly behind the drink holder or within the drink holder itself.
For more details about Hoppy issues with a Generation II Volvo check the following discussion To Hoppy or not to Hoppy?.
The Proper Way to Wire Conventional Tail Light Converters:
As mentioned above you cannot use a retail version tail light converter on 2003/2004? and up Volvos.
The schematic also details pretty much everything you need to know about the electrical basics or setting your new truck up as an RV/Toter and this also includes wiring additions/upgrades that you want to make on the newer Volvo's.
With this setup and a commercial ASME socket in lieu of a standard 7 blade plastic RV style socket on the rear of your truck the use of two short homemade pigtails would allow you to tow someone else's 5er that is wired with a conventional plastic 7 blade RV style plug or for someone else to tow your 5er if they had a conventional plastic 7 blade RV style socket on the rear of their toter.