Ford F-150 Negative Battery Terminal Concern

Discussion in 'On the Road' started by K3WR, Sep 20, 2017.

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  1. WA7PRC

    WA7PRC Ham Member QRZ Page

    Over time, vehicles with positive grounds disappeared. As this happened, manufacturers stopped using the more-expensive and more-complicated floating negative power bus system.

    Many vehicle manufacturers, and most aftermarket equipment manufacturers, never re-thought the systems others were using. Manufacturers carried over the acceptable negative fuse idea appearing in ground independent power buss systems, which could also use a negative battery post connection. Manufacturers misapplied the allowable fused negative battery post connection to equipment with internally grounded negative bus systems.

    Not realizing the safety hazard, they continued to fuse both negative and positive radio power leads and often advised direct battery post negative connections. The battery post connection actually created ground loop, fire, and equipment safety hazards.

    This terrible idea has permeated the aftermarket accessory market, including amateur radio, audio, and performance or race car electronics markets. For example, MSD Ignition's installation instructions advise a direct battery post negative connection, putting the vehicle's distributor, the MSD box, and other electronics at risk.

    Although absolutely incorrect, a popular assumption is fusing the negative lead can protect internal and external equipment wiring, including gauge, computer, speaker, microphone, key leads, and antenna connections from open battery ground connection damage.
    My mobile installations have always had the negative lead from the rig connected directly to chassis, near the rig. It's not possible for a blown fuse to allow a high current return path via other path(s). The ONLY fuse(s) are in the positive lead, with a fuse AT the source.
    W4JFA, AI7PM and W5WTC like this.
  2. W5WTC

    W5WTC Ham Member QRZ Page

    Thanks I will research further, that was an interesting link to read. has me rethinking my installations. I was always told to fuse both wires on sensitive radio equip. after all the harness on my mobile yaseu 857 comes pre wired with fuses on both at the attachment ends. after this read it makes sense not to.
    Last edited: Sep 29, 2017
  3. WD8RIT

    WD8RIT Ham Member QRZ Page

    I grounded my IC-7000 to the battery in my 2016 F-150. No issues.
    N5RLR likes this.
  4. AI7PM

    AI7PM Ham Member QRZ Page

  5. WA7ARK

    WA7ARK Ham Member QRZ Page

    There is usually a high-current spare fuse holder there. There might be a "always-hot" spare, or one that is powered only with the key in the "accessory" position. The latter usually goes off during cranking, which is what you want to protect the radio.

    There may be a ground terminal near the fuse block; more likely not, in which case the black wire should be connected to the car structure as close to the radio as possible. If you are doing that, get rid of the fuse holder in the radio's black power wire. It was added only because naive installers insist on running the black wire directly to the negative battery post, and if the battery ground strap looses contact, you will burn up the radio during the next start. That wont happen if the radio is grounded to the car body close to where the radio is mounted.
    W4JFA and AI7PM like this.
  6. K6BRW

    K6BRW Ham Member QRZ Page

    On current generation F-150s (I have a '17 SuperCab 4x4 XLT with the 3.5 EcoBoost) this is a horrible place to get power. They aren't wired like they used to be. The power comes from one of the control modules and is just a few amps and are like a 16-18awg wire. It will also only come on when the truck senses a trailer connected correctly. The new "Smart Trailer Connection" or whatever they call it can be a bit dumb. When these trucks came out many people returned to a head scratching dealer to figure out what was going on.

    I ended up sourcing positive at the battery and grounded to the body.
  7. W5WTC

    W5WTC Ham Member QRZ Page

    Yes I agree, I now that I have a new 2017 F250 my opinion has changed. I find the trailer connection to be too “smart” for this ham when I tried to use it to tap power some camping accessories. It is nice that it will tell you what trailer light might be malfunctioning though but not a good tap for power other than for the towed trailer. I found the aluminum cab and bed to be more of a problem. Couldn’t get my mag mount to attach. Forced me to do the install with an antenna bracket that mounts in the hood seam to the engine compartment. Turned out it works better than my old mag mount. Got my power running through the 40 amp upfitter switch and fused at the radio. So far, my 857 has found no noise problems.
    KD0XL likes this.

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