How To Connect Trailer With 5-Flat To Vehicle With 4-Flat
Updated 09/29/2025 | Published 04/30/2025
Question:
I have a 4 wire flat lights connector on my car, and a 5 wire flat lights connector on my trailer. I see conversions for 5 car to 4 trailer, but not the other way around. Are there any converters to address my need, or do any of the 5 to 4 converters work backwards?
asked by: Bob S
Expert Reply:
Hello Bob, thanks for reaching out. The 5th wire your trailer has is a reverse light circuit. We do sell a wiring kit that will allow you to add a reverse light circuit to your vehicles 4-flat to upgrade it to a 5-flat. For that, you can use the following:
Curt Trailer Connector Adapter - 4-Way Flat to 5-Way Flat - Vehicle End # C57187
(click to enlarge)
Product Page this Question was Asked From
Curt Trailer Connector Adapter - 4-Way Flat to 5-Way Flat - Vehicle End
- Custom Fit Vehicle Wiring
- Wiring Adapters
- Universal Fit
- 4 Flat to 5 Flat
- Plug and Lead
- CURT
more information >
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Jesse M.
9/26/2025
Hey Bob, did the wiring kit work out for upgrading your car's connector to a 5-flat? I'm curious to know if it solved your issue, as it could help others with a similar setup.