Why Does 4-Pin Trailer Wiring Have 5 Wires
Updated 02/16/2024 | Published 06/19/2019
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Question:
Please help! I have a 4 pin with 5 wires, W-R-B-Y-G. I have two trailer lights to wire to... Left: R-Y-B Right: R-G-B I know the White from 4-pin is the ground. But the G/B wire from the pin and R/Y wire from the pin are confusing me. If I wire the R/Y on the left to their respective colors, then I have the Brown left alone. Where as, if I wire the G/B on the right, I am left with the Red. Im at a loss. See attached photos below. Thanks!
asked by: Paul M
Expert Reply:
Your 4-pin/5-wire wiring harness is what is called a "wishbone" type which simply means that there are two separate running light wires, one brown and one pink. This allows a separate running light wire for each side of the trailer which saves you having to run a jumper wire from one side of the trailer to the other. We offer lots of wiring items just like this, such as # A35W42B, # A20WB and # A10-4225VP, which happen to use two brown wires instead of one brown and one pink.
The functions of the 5 wires is as follows: WHITE is ground (as you stated); PINK and BROWN are for running lights; YELLOW is for LEFT stop/turn; and GREEN is for RIGHT stop/turn.
Your trailer lights may use wire colors that do not match these so this is why you always want to wire by function rather than by wire color. The lights may be labeled to tell you which wire handles what function but you can always test this with a 12V battery. You can also refer to the linked article on trailer wiring which has lots of detailed information that will help you wire the lights.
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16 Gauge, 4 Conductor Bonded Parallel Wire - Per Foot
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- Bonded Wire
- 4 Wire
- 16 Gauge
- Deka
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Tracy W.
2/14/2024
Thank you so much for your expert advice. You have helped me save hours trying to figure out this 5 into 4 wire problem. Your explanation is so easy to understand too. Thank u, thank you. Thank you!