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Customer Reviews

Trailer Wiring Frequently Asked Questions

Written by hitchweb Team
Monday, February 6, 2012 — 8 Comments

Hitchweb has put together an article that answers the most frequently asked questions about Trailer Wiring:

Q. What do I do if my trailer has dual bulbs and my vehicle only has one?

A. If the trailer has dual bulbs and the vehicle only has one, make sure they are wired for a 6 or 7 way and use the 118158 reverse converter.

Q. If the trailer light has a license light - is it a left or right?

A. Licence lights go on the left side of the trailer, no license light goes on the right side.

Q. Are 7-pin to 7-blade Adapter available?

A. 7-pin to 7-blade Adapters are no longer available. They are not common in the industry, Ford only used them for 2 years.

Q. Is there a 24V to 12V Adapter?

A. No, it does not exist. To hook up the running lights, change the bulbs on the trailer to 24V bulbs (available from Automotive) and use a 24V Converter.

Q. Are 5-4 Adapters still available?

A. No longer available. You can still plug the 5 prong into the 4 prong, but the reverse (5th prong) will not work.

Q. How do I hook up two 7-blades on a truck?

A. Purchase 2x 5th wheel harnesses. 1 end of each harness plugs into the truck and the other end of each harness plugs into each other. See image to the right:

Hook up two 7-blades on a truck

Posted in Towing 101


Hitchweb Team
Tuesday, September 18, 2018
Hello Mr. Kraus. Curt Manufacturing offers a 7 way to 7 way trailer connector that will plug into your truck's OEM outlet. This is part number 55774, and is found in our hitch search category here:
Bill Kraus
Tuesday, September 18, 2018
Have 2017 3500 High country Silverado Short Box. Has factory tow phkg. I want to put camper on it and pull boat. Does anyone make a 7pin male to two 7pin female adaptor ?
Hitchweb Team
Thursday, October 13, 2016
Hello, No, you do not need to purchase a trailer wiring harness if you only intend to carry a bike rack.
Thursday, October 13, 2016
Do I need wiring when I just want to use the itch to mount only a bike rack (no trailer)?
Hitchweb Team
Tuesday, April 12, 2016
A 7 to 5 adapter Adapts a 7-way RV blade vehicle socket to fit 5-way flat trailer plugs. What are you looking to do?
Tuesday, April 12, 2016
will a 7 round to 5 flat adapter work with a 4 flat plug?
Hitchweb Team
Monday, May 25, 2015

Hello Mr. Demchuk, Thank you for your patience while our systems became available again. I show the following part numbers for your 2003 Volkswagen Passat: Wiring Harness with Powered Converter: #119180 4 to 7 Blade Adapter #75321

Paul Demchuk
Monday, May 11, 2015

Hi: I just ordered a hitch for my VW Passat. The car requires a wiring adapter to make the trailer lights work. (I have done this before on another Passat I own). However, the trailer I am purchasing has a 7 pin circular connector while the typical Passat adapter provides only a 4 pin connector. Can you advise me of the correct products to order so that I can use the 7 pin on my new trailer? Thanks.

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