Do 7-Way Trailer Connectors have Amp Ratings for Pins or the Whole Socket
Updated 09/04/2025 | Published 07/19/2017
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Question:
I have a RV hookup cable for the tow vehicle that has different gauges of wire for the seven wires. The black power / charge wire and white ground wire are both 10 gauge. Does this part have a specification rating for continuous or intermittent use in amps per pin or the entire assembly? I would like to the correct circuit breakers to protect the pins and socket from overheating. The connection would charge the RV battery while the engine is running.
asked by: Wade
Expert Reply:
Most if not all trailer wiring harnesses/connectors use larger wires for the 12 volt and ground circuits compared to the other circuits (lights). The sockets themselves don't have an amperage rating so you will go by the draw of the things drawing power.
In order to figure out what the lights are drawing you could connect the trailer to the tow vehicle and turn on a function while testing the trailer side wiring behind the connector with a meter to see what sort of reading you get. Usually running lights (including tail lights, clearance lights, and marker lights) draw around 7 to 10 amps unless they are LED lights. Brake lights and turn signals are usually 2 to 3 amps and are combined on the same circuit.
For a 12 volt circuit we recommend a 40 amp circuit breaker # PK54540. For a brake controller I recommend a 30 amp, # PK54530. And if the trailer has reverse lights it will be less than brake and turn signals so maybe 5 amps total.
Unless there is a short though the wiring, pins, and sockets are not likely to ever overheat during normal operation. Also, the 12 volt circuit on a 7-Way can only provide a maintenance charge to a trailer battery. The only time it can charge it up is if it is a breakaway battery which would have a 5 amp hour rating. The wiring is not large enough and the alternators on most vehicles is not strong enough to push back the required amperage to charge up a regular sized 12 volt battery. To do that you would need a Dual Battery charger like # 331-BCDC1240D.
Wayne V.
9/3/2025
Hello Michael, Thank you for that information. I have a similar question about current rating on the 7 pin trailer 12V aux pin. It seems to me that if the 12v batteries on an RV trailer were low, or dead(worst case), when you hooked up the trailer to the tow vehicle, the 12V circuit would see almost a short circuit blowing the 12V tow vehicle 40A fuse. It seems there should be a limiter circuit in line, similar to that of a battery charger. Any thoughts ? Of course the best thing to do before hooking up, is making sure the trailer batteries are topped off. Thank you, Wayne
Jesse M.
9/4/2025
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Robert S.
7/20/2020
I bought the curt echo brake controller, which lights off another vehicle but notthe one I am installing on. Ihave the 12 to the brake pins but not the battery pin (I only have 20 amps) is that why the led will not light? Does it require aux power and brake power? thanks