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.
The best price I've found for the
Hoppy 46255 and the
Hoppy 46365 tail light converters is at
PartsAmerica.com and the
Hidden Hitch Powerline 5 Amp "LITE/#HH31825" - 10 Amp
"SMART/#HH31824" and the 20 Amp "HD/#HH31826" line of tail light
converters are available at
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
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.
To Hoppy or not to Hoppy? go into more thorough details about this issue with newer model Volvo's.
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:
This schematic details how to wire a Hoppy 46365 including how to properly wire it so
the OEM ICC Marker Light Switch on your dash will blink your 5th-Wheel's running lights.
As mentioned above you cannot use a retail version tail light converter on 2003/2004? and up
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.
From 5th_Wheeler (Jon):|
If you click on the thumbnail picture to
the left, it
will take you to my WebShots folder with a dozen or so pictures on
how 2BTRVLN (Charlie) and myself wired his Hoppy 46365 Powered
Converter and BrakeSmart Brake Controller using two ASME Commercial Plugs so that he still
retains an ASME Commercial Socket on the rear of his cab should he ever need to pull a
commercial trailer and a seven blade RV Socket to pull his 5er with. By simply
unplugging one ASME Commercial Plug and inserting the other ASME Commercial Plug into the
ASME Commercial Socket in his side electrical compartment he has trailer lighting capabilities
for both a Commercial Trailer and for his 5th-Wheel.
photos of the clean looking electrical upgrades
that he did in his VNL770 that also includes photos of many of the items that he used for his
This schematic shows how to wire your electrical compartment for dual function hook-ups.
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.
are the homemade pigtails that are required for the dual function electrical
More Converter Wiring Schematics:
Jack Mayer's Schematic
Mark Bruss' Schematic
Jack Mayer (Jack) and
Mark & Dale Bruss (Mark) have hoppy wiring articles on their web sites.