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Trailer power plug

Discussion in 'On the Road' started by K8INA, Aug 9, 2016.

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  1. K8INA

    K8INA Ham Member QRZ Page

    Hello all,

    I would like to be able to use my mobile rig from the tailgate of my 2015 Ram truck. It is wired From the factory with the large round connector that allows for brakes and charging the trailer battery from the truck. My thought is to purchase another plug and wire it for my rig. The problem is, I cannot find what current the various connections are rated for. I have checked with the service techs and they "guess" 20 amps. Does anyone know for sure? I think this would be an easier way to go over running temporary cable from the battery.
    Thanks in advance
  2. KC9UDX

    KC9UDX Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    It might not be better.

    I'd guess 20A, too, but none of our guessed mean much.
  3. AC0GV

    AC0GV Ham Member QRZ Page

    It should be listed as trailer charge or 12v+ in your book. The Ford that I just sold was a 30 amp.
  4. KD2IAT

    KD2IAT Ham Member QRZ Page

    Look in the manual for your truck on the fuse page. Trailer Charge (or similar words) will be a fuse somewhere on one of the fuse blocks. What ever that factory fuse rating is will be what the pin on the connector is rated for. Given the size of the wires used by the truck manufacturers, I would tend to stay under the factory rating by about 5 amps.

    FWIW, that line is almost certainly controlled by a relay which requires Ignition or Run/Accessory. That way, what ever is connected to it won't run down your truck battery when the truck is off.
  5. KA9JLM

    KA9JLM Ham Member QRZ Page

    I would go to Autozone see what Your connector is rated for, The size of wire gives a clue.

    If your harness is only rated for electric brakes and lights, I don't think it will power a 100 watt radio very well. With a Big capacitor on SSB it may work fair, But that could weld the relay contacts if it uses one.

    The main power on my truck is always on and has a fuse under the hood. It is a FORD. I fixed it yesterday.

    Have fun.
    Last edited: Aug 9, 2016
  6. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

    Yes most have 30 amp it will work
  7. W4KJG

    W4KJG Subscriber QRZ Page

    You should be able to go to the fuse blocks (my truck has two fuse blocks). Mine have covers with markings showing function and fuse size. My cargo trailer has its own battery and I use a wireless brake controller. The brake connection to the trailer only provides charging current. I believe it is fused at 20 amps.
  8. KF5FEI

    KF5FEI Ham Member QRZ Page

    Just an FYI for those who are only familiar with the simple connectors for trailer lights, the connector he is referring to is the one for big trailers that has extra connections for trailer brakes and charging the house batteries on a camper trailer. He's not trying to run his radio off one of the light connections.

    I definitely would check the wire size and estimate the length -- even though it may be fused for 20 or 30A, you may have considerable voltage drop if you run an HF rig off of it at full power. And as others have mentioned, it may be switched so you can't discharge the vehicle battery. One option might be to mount a deep-cycle battery in a box in the back corner of the bed and charge it from this connector.
  9. W0IS

    W0IS Ham Member QRZ Page

    This might seem like a dumb question, and you can ignore it if you've already checked. But are you sure the connector is wired for charging the battery? In some cases, the connector is not wired for charging, and you need to add the charge line as an extra option. So if you've never used the connector for charging, before you dig too deep, it would be a good idea to check it with a voltmeter and make sure that connector really has 12 volts going to it.

    If it does, I'd go along with the other two votes and cast a guess of about 20 amps. But I really don't know. :)
  10. KA9JLM

    KA9JLM Ham Member QRZ Page

    I guess they did not make a manual for that auto.

    That sucks. That is the first thing I buy. I read it too.

    So far guessing has been fun. Who gets the cigar ?

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