Adding a Charge Line Circuit To a Trailer With a 4-Way/5-Way Flat Connector

Updated 11/22/2021 | Published 11/21/2021

Products Featured in This Question

16 Gauge, 4 Conductor Bonded Parallel Wire - Per Foot

(237)

$1.99

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

(149)

$55.39

Buyers Products Trailer Connector Adapter - 4-Way to 7-Way RV and 4-Way Flat

(180)

$19.20

Adapter 4-Pole to 5-Pole Trailer Wiring Adapter - Shorter

(222)

$10.94

Deka Heat Shrink Butt Connector - 16-14 Gauge - Nylon Insulation - Blue - Qty 5

(1110)

$8.45

Deka Heat Shrink Butt Connector - 12-10 Gauge - Nylon Insulation - Yellow - Qty 5

(1110)

$7.45

7-Way Molded Trailer Wire Connector, 6' Long

(394)

$44.94

Question:

2010 Prius-12v battery in the rear. I want to wire my trailer 5 Flat it has an onboard 12v air compressor with a 20 amp draw to raise and lower the deck. There are NO trailer brakes. My Prius is being trailer wired. My Teknosha 118505 will be wired to the 12v positive post and grounded as per included video instructions. My 4 to 5 Hopkins adapter # 47515 has the blueinch wire for the reverse light. Im concerned that the amperage draw of 20 amps is too much for the 4 to 5 flat adapter. My initial plan was to replace the blue wireinch on the 4 to 5 adapter with a 10 gauge wire and run to the rear 12v battery positive post with an inline 12v 25 amp re set circuit breaker. Will this strain the load on the Teknosha 118505 as it will be also hooked up to the prius 12v positive connection and it will share the ground connection. Any thoughts? The image is the plug from the trailer...which supplies power to the compressor in a normal 5 flat to 5 flat connection.

asked by: Dave V

Expert Reply:

I recommend moving away from the Adapter 4-Pole to 5-Pole Trailer Wiring Adapter # 47515 and going with a Buyers Products Trailer Connector Adapter # 337TC1474P. The wiring and connectors used on the 4-way harness are not designed to be used with the 20amps of power you will putting on the connector. The 4-way/5-way connector cannot handle the additional strain and it will likely overheat with the amperage and risk causing an electrical fire.

With the Buyers Products Trailer Connector Adapter # 337TC1474P you will be able to connect your Tekonsha T-One Vehicle Wiring Harness # 118505 directly to the 4-way on the Buyers Adapter. The Adapter will give you a seperate 7-way connector while still retaining a 4-way flat for other uses. You will then be able to run the additional 10 gauge wiring for the charge line and ground. The 7-way will be much safer as it is designed to handle the amperage you are going to use.

You will be able to change the trailer connection to the 7-Way Molded Trailer Wire Connector # H20044 which also uses 10 gauge wire for both the ground and charge line circuit. This ensures that all of the wiring you are going to use is the correct gauge to handle the amp draw.

Be sure to use Heat Shrink Butt Connectors # DW05745-5 and DW05744-5 for the connectors to protect them from any corrosion.