How can a 4 flat wire vehicle tow a 7 blade trailer?

Matt.H

Matt.H

Adventurer
I hope there is a simple adapter that I can't find. :confused:

My truck and trailer has the typical 7 blade wiring harness. Often I am asked if various family can borrow my trailer. Without rewiring the tow vehicle(s), and leaving their vehicles flat 4 way is their anyway to easily adapt the connection?
.
The trailer in question does not have brakes. It is using the extra wires for reverse/backup lights and charging a battery. The brake wire on the trailer is not hooked up, (on this trailer).
I am actually thinking of upgrading the lighting in the trailer to LED so I would not be against a wiring harness for the trailer that could plug into both 7 and 4 way at the tow vehicle. Does such a thing exist?

Thanks.
 
Last edited:
Q

quickfarms

Adventurer
What type of trailer?

The 7 contact connector comes in two varieties, round pin is commercial, flat blade is for rv.

Typically a trailer with 7 blade connector may have electric brakes

A vehicle with the four flat connector usually is not wired for electric brakes
 
Matt.H

Matt.H

Adventurer
arz said:
Need some sort of brake controller in the vehicle.
Click to expand...
The tow vehicle has a brake controller. However it is not in use on this trailer. See below.

quickfarms said:
What type of trailer?

The 7 contact connector comes in two varieties, round pin is commercial, flat blade is for rv.

Typically a trailer with 7 blade connector may have electric brakes

A vehicle with the four flat connector usually is not wired for electric brakes
Click to expand...

Dodge Ram factory 7 blade.


.

The trailer in question does not have brakes. It is using the extra wires for reverse lights and charging a battery. The brake wire on the trailer is not hooked up, (on this trailer).
 
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P

peekay

Adventurer
Matt.H

Matt.H

Adventurer
Mccool said:
Here you go

https://www.amazon.com/Trailer-Adapter-convert-trailer-97015/dp/B000WG83HO
Click to expand...

peekay said:
that device the prior poster referenced from Amazon is exactly what you need. It's not a permanent mod. It's just an adapter.
Click to expand...

Thanks, I wish he had stayed on.

So, I assume that I would use the ground-wire and leave the others hanging? Yes? It looks like a cheap fix if I can get it to work. If not I can say I have tried.
.

Thanks to all that took the time to read the OP.
ExPo is always a wealth of information. Even when you don't see it when placed in front of your face.:ugh::********:

Matt
 
M

Mccool

Observer
Matt.H said:
Thanks, I wish he had stayed on.

So, I assume that I would use the ground-wire and leave the others hanging? Yes? It looks like a cheap fix if I can get it to work. If not I can say I have tried.
.

Thanks to all that took the time to read the OP.
ExPo is always a wealth of information. Even when you don't see it when placed in front of your face.:ugh::********:

Matt
Click to expand...


You don't need to do any permanent wiring, those extra wires are for the brakes. It should work fine for your needs. Obviously, the reverse lights and battery charging won't work.

Best of luck.
 
80t0ylc

80t0ylc

Hill & Gully Rider
Matt.H said:
I hope there is a simple adapter that I can't find. :confused:

My truck and trailer has the typical 7 blade wiring harness. Often I am asked if various family can borrow my trailer. Without rewiring the tow vehicle(s), and leaving their vehicles flat 4 way is their anyway to easily adapt the connection?
.
The trailer in question does not have brakes. It is using the extra wires for reverse/backup lights and charging a battery. The brake wire on the trailer is not hooked up, (on this trailer).
I am actually thinking of upgrading the lighting in the trailer to LED so I would not be against a wiring harness for the trailer that could plug into both 7 and 4 way at the tow vehicle. Does such a thing exist?

Thanks.
Click to expand...
Looks to me like all you need is to add this connector (or equivlent), to your existing 7 pin connector on your trailer. You'll need to tap into the wiring, to do this, but it's the simplest way to do it, since an adapter to do what you want, either doesn't exist or is extremely hard to find - which would make it expen$ive.
https://www.amazon.com/Reese-Towpow...rd_wg=9O9Gx&psc=1&refRID=158BA3TEAW2DB9D82GES

Then, the tow vehicle can choose which connector to use, depending on what they have. Be sure to stick to the wiring standards for each type. This is a good reference (lot's of info & links):
https://www.etrailer.com/faq-wiring.aspx

Also, be sure to have a cover for each connector and to keep it in place on the unused one when towing to keep dirt & moisture out. It's a good idea to keep the unused connector tied up tight so it doesn't drag and get damaged.
Edit: The reason you won't find an adapter is that 99.9% of trailers that have a 7 pin connector on them have existing brakes wired up and need to be plugged into a 7 pin vehicle connector to work. It's a safety issue - so to get around this is an uncommon and unique situation requiring an uncommon fix.
 
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Jmanscotch

Jmanscotch

is wandering
I didn't look at Toms links, but it sounds simular to what I'm doing.

I too have a main tow rig with a 7 blade and thus and wiring my trailer to benefit from that (reverse lights and 12v power) but I realize I might need to tow the trailer with something with only a 4-pin.

My solution is adding a junction box (On eTrailer/Amazon, made specifically for a 7 pin trailer wiring) and I'm running BOTH a 7-blade and 4-pin connector forward from the junction box so both will run the lights (all LED). I'll zip tie the 4 pin out of the way (with a cover) for the majority of the time.

$15 for the junction box and $10 for the 4-pin harness. Figured it was a pretty affordable fix to an annoying problem.
 
WOODY2

WOODY2

Adventurer
It would be easy to fab up a pigtail. You would need a 7 blade FEMALE receptacle and a MALE 4 pin with the wires molded in. Just install the 4 wires to the back of the 7 blade, tape it up and voila you're done. You can then stow it for later use by those doomed to just 4 pin connector. PM me and I will send you a pic
 
80t0ylc

80t0ylc

Hill & Gully Rider
WOODY2 said:
It would be easy to fab up a pigtail. You would need a 7 blade FEMALE receptacle and a MALE 4 pin with the wires molded in. Just install the 4 wires to the back of the 7 blade, tape it up and voila you're done. You can then stow it for later use by those doomed to just 4 pin connector. PM me and I will send you a pic
Click to expand...
My question would be: Why fab something up, using multiple connectors, when a $5 connector wired in correctly will do the job? It's simpler and has less splices which are possible failure points. Plus, almost zero chance to get lost. Once again: https://www.amazon.com/dp/B000CPCC3Q?tag=viglink20599-20
Edit: If 12" is not long enough for the wires on this connector, the same connector is available with longer leads.
 
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WOODY2

WOODY2

Adventurer
80t0ylc said:
My question would be: Why fab something up, using multiple connectors, when a $5 connector wired in correctly will do the job? It's simpler and has less splices which are possible failure points. Plus, almost zero chance to get lost. Once again: https://www.amazon.com/dp/B000CPCC3Q?tag=viglink20599-20
Edit: If 12" is not long enough for the wires on this connector, the same connector is available with longer leads.
Click to expand...

Thats 1/2 of the equation, if that's all he needs what is he going to plug the male 7 blade on the trailer into? When I bring up the Amazon link it shows a 7 blade male, I'm advocating a female version
 
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