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Wiring lights for flat tow vehicle


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I plan to tow a 2021 Jeep Grand Cherokee and purchased a custom wiring harness from Blue Ox for that specific model.  The harness connects to the rear lights and runs to the front of the vehicle where it terminates with a four wire flat plug.  The directions suggest mounting the flat four-wire plug on a frame crossmember near the upper front portion of the engine compartment.  They then supplied a four foot wire with a male four-wire flat plug on one end and a female four-wire flat plug on the other end.  This wire is somehow supposed to connect the towed vehicle to the motor home.  Lots of things wrong with that, my motor home does not have a four-wire plug, only a seven-wire and then four feet is not nearly enough wire to go from the towed vehicle to the motor home.

So what kind of setup do most people have to connect their towed vehicle wiring to their motorhome?  I've considered a 7 to 4 cable and I've considered installing a six wire plug in the lower grill, cutting off the four-wire flat plug and connecting those wires to the six-wire plug and then use the more standard 7 to 6 wire cable.  

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When we were towing with a motorhome I installed a set of brake/turn lights that were not part of the vehicle being towed. On the first the lights were mounted to the bumper of the twoed vehicle, in the case of the two Honda CR-V's I put a second brake/tail light into the plastic that housed the vehicle's lights.  In all 3 cases I then ran a wire harness that I built to the front grill where I installed one of the 7 wire connectors in the grill with the 12V wire supplying 12V to keep the battery charged. I didn't use the extra pins and I made my own custom connecting harness to go between the two vehicles. 

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We used high quality magnetic used by towing trucks for our 2018 Equinox.  We run the cable through the tailgate through the spare wheel pan down along the body to the front.  They were highly visible and easy to remove when not towing.

 On the 1994 Grand Cherokee we added bulbs in the taillight housing as they were rather large.  On the 2012 Equinox we tried adding bulbs but the taillight housings were not suited to adding bulbs, too thick, and we had terrible water leakage. We had successfully used a diode harness on the 2014 Equinox.  The 2018 Equinox taillights were not suited for a diode harness. 

I used a 7-flat bladed round connector into the Bounder and a 5-pin flat plug into a bracketed receptacle near the tow bar.  The 5 pin gave the +12v line to keep the battery charged.

When we had the Grand Cherokee, we use a 7-flat bladed round connection into the Jeep as we had space for the connector body. 

I do not like the 6-pin round plug, just like the 4-pin round plugs.  The sleeve connectors in the receptacle are prone to slipping into the connector giving bad contacts.  I do not like loosing the taillights in tow.

 

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We just changed our toad from an aging Jeep to a new Ford Ranger.  We have an all Blue Ox configuration.  The base plate installation was straightforward, but the real challenge was in the taillight wiring.  I was very fortunate to have a brother-in-law who is a mechanic and he has quite a bit of experience in wiring issues.  There are just lots of options in this stuff.

The Blue Ox wiring kit instructions were of limited use.  But, etrailer.com has some very detailed videos on the process.  That saved our bacon.  We ignored the Blue Ox instructions and just did what the etrailer installer did.  Our installation was made more complex because of LED taillights and highly featured taillight modules.  But, it worked fine.  And, sadly, just hiring someone to do this for you doesn't always work.  Sometimes those 'experienced' tow system installers are anything but 'experienced' and are learning on your time.  

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Mark, I made my own cable and connectors from the RV to my toad, here are some considerations that are critical.

1) Is the RV a so called Three Wire (Left Turn & Stop, Right Turn & Stop, Tail/Marker) orrrrrrrrr a so called Four Wire  (Left Turn, Right Turn, Stop, Tail/Marker) with separate (often amber) turn signals, NOT combo Turn & Stop

2) Is the Jeep (as I suspect) a Four Wire or an older style Three Wire with combo turn and brake lights ???

3) They make 3 to 4 wire solid state black box adapters and they make 4 to 3 wire adapters IF needed. 

5) What I had to do (3 wire RV but 4 wire Toad) was use a 3 to 4 adapter but yours may be different.

6) On the rear of my RV I used the 7 pin round female receptacle and my own cord with a male Plug on its end to fit into the female connector on my Toad. I keep the RV end plugged in and when I hook up the Toad all I have to do is grab it and plug it into the front receptacle on  my toad, easy peasey. I prefer the 7 pin RV type round plugs and receptacles farrrrrrrr over old flat style, old were 4 pin now they make 5

You can buy 6 or 7 conductor cable as well as all the plugs and receptacles and adapters on e trailer. I did much better fabricating up all my own systems, but Im sort of experienced and into that sort of thing.

NOTE there are different ways to do this, the above is only how I chose

 John T

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My coach came with a 6 pin round and the Road Master Sterling All-Terrain tow bar came with the 6-pin round plugs.  I use the magnetic lights on my Jeep Cherokee and just run the cable along the roof rack and then under the hood by the wipers.  I mounted a 6-pin connector at the front of the Jeep and used one of the 6 wires for my Air-Force One brake system and then used 4 of the remaining wires to connect a flat four connector that permanently sets under the hood.  This is the connector I plug my magnetic tail lights into.  I also did this on my old Ford Focus and have had no issues with this system since I set it up originally in 2009.  One connection under the hood and one connection at the front of the Jeep and I am on my way with the Tail Lights and on-board braking system hooked up and ready to go.

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Thanks for all the comments, seems like no one likes the flat connectors and opts to the 6 or 7 pin.  My wire harness is supposed to just plug into the existing tail light system, so I'm hoping that all I need to do is plug them in and run the wire to the front.  Looks like I may then cut off the flat 4 wire and install a 6 wire.  My brother is helping and he is a Jeep/Chrysler mechanic.

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2 hours ago, MarkB said:

Looks like I may then cut off the flat 4 wire and install a 6 wire.

That should work as long as it is connected properly. Keep us posted on how things go and do not hesitate to open new threads at any time.

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On 2/24/2021 at 7:57 PM, MarkB said:

I plan to tow a 2021 Jeep Grand Cherokee and purchased a custom wiring harness from Blue Ox for that specific model.  The harness connects to the rear lights and runs to the front of the vehicle where it terminates with a four wire flat plug.  The directions suggest mounting the flat four-wire plug on a frame crossmember near the upper front portion of the engine compartment.  They then supplied a four foot wire with a male four-wire flat plug on one end and a female four-wire flat plug on the other end.  This wire is somehow supposed to connect the towed vehicle to the motor home.  Lots of things wrong with that, my motor home does not have a four-wire plug, only a seven-wire and then four feet is not nearly enough wire to go from the towed vehicle to the motor home.

So what kind of setup do most people have to connect their towed vehicle wiring to their motorhome?  I've considered a 7 to 4 cable and I've considered installing a six wire plug in the lower grill, cutting off the four-wire flat plug and connecting those wires to the six-wire plug and then use the more standard 7 to 6 wire cable.  

It may be less work and money to buy a 4-pin to 7-pin adapter plug.

 

4-Way Flat to 7 Way Round RV Blade Wiring Adapter Trailer ...

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On 2/27/2021 at 8:10 AM, MarkB said:

Thanks for all the comments, seems like no one likes the flat connectors and opts to the 6 or 7 pin.  My wire harness is supposed to just plug into the existing tail light system, so I'm hoping that all I need to do is plug them in and run the wire to the front.  Looks like I may then cut off the flat 4 wire and install a 6 wire.  My brother is helping and he is a Jeep/Chrysler mechanic.

Make sure you also have the diodes for the lights so you don't get feedback. Should come with the wiring kit.

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Other consideration of the unibiqual to the car.  On the  Bounder we had to use a drop hitch adapter to get the proper height.  That put the car farther away from the Bounder.  Even with carefull shopping, the longest spiral cables I could find were 7 '.  My solution was to mount a 7-flat receptacle on the drop down adapter using clamps with a short cable to the Bounder.  Now the cable was comfortable.

Using the magnetic lights was a simple 4 wire cable.  The lights were easy.  But we also were using a battery charger with the +12volt wire.  The charger assumes a ground connect between the tow vehicle and the toad.  This is normally supplied via the light wiring.  I had to insure the White (Ground) wire of the light wires was attached to frame ground of the Equinfox for the charger to work.

D were 7'.

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