trailer brakes locking during backup

Discussion in 'Trailering' started by boatman37, May 22, 2019.

  1. boatman37

    boatman37 Well-Known Member

    Jun 6, 2015
    pittsburgh
    2006 Crownline 250CR. 5.7 Merc BIII
    Previous: 1986 Sea Ray 250 Sundancer. 260 Merc Alpha 1 Gen 1
    5.7 Merc BIII
    Bought a new 2018 2500 Ram a couple weeks ago and towed the boat today for the first time. I have the 5 pin to 7 pin adapter and it worked fine with my last truck. Today with the new truck my trailer brakes were locking up every time I tried to back up. Read something on etrailer.com that said the lockout pin is the center pin on the 7 prong plug. I have no power at the center pin (this was tested without the trailer plugged in). I did read that there should be a fuse under the hood but I'm not sure which one it should be? Anyone else run into this issue? The truck has the built in trailer brakes but these don't function with the boat trailer since there are no electric brakes.
     
  2. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    PA
    Various
    Various
    Put it in reverse and see if you have +12V on the blue wire (5th pin). Just pull the trailer connector apart enough to get your DMM lead onto the metal pin. Start with that and post back. Obviously, don't run yerself over while doing this! You can also jump +12V to the blue wire and listen for the backup solenoid to click. You didn't mention it, but I'm assuming you have disc brakes since you mentioned a 7-5.
     
  3. Espos4

    Espos4 Well-Known Member

    979
    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    Please clarify, does your trailer have electric brakes or surge brakes?

    Can you post a picture of the coupler?

    Surge brakes should have some sort of mechanical lock out for operating in reverse.
     
    Captn TJ likes this.
  4. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    PA
    Various
    Various
    And, as Espos4 mentioned, until you get it figure out, just use the mechanical lockout feature. Post a pic of the coupler if you're not sure how to do it - there are different styles of couplers with different ways to lock it out.
     
  5. boatman37

    boatman37 Well-Known Member

    Jun 6, 2015
    pittsburgh
    2006 Crownline 250CR. 5.7 Merc BIII
    Previous: 1986 Sea Ray 250 Sundancer. 260 Merc Alpha 1 Gen 1
    5.7 Merc BIII
    It does have disk brakes. I don't have any pics of the actuator but will get some tomorrow. I don't see anywhere to mechanically lock it out. It's a 2016 Venture aluminum tandem axle trailer if that helps.

    Brakes are surge. When I back up the coupler applies the trailer brakes like it should. The 5 pin to 7 pin adapter locks out the solenoid on the trailer that activates the brakes. According to e trailer site the center pin should be used for this? The center pin is for reverse lights so should be wired to the reverse lights on the truck. The blue wire is for the trailer brakes. I don't have electric trailer brakes so this one would be unused?

    https://www.etrailer.com/question-6223.html
     
  6. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    PA
    Various
    Various
    The blue wire on your trailer side is connected to the brake solenoid. It get's it's feed when you put the vehicle in reverse.
     
    Leardriver likes this.
  7. boatman37

    boatman37 Well-Known Member

    Jun 6, 2015
    pittsburgh
    2006 Crownline 250CR. 5.7 Merc BIII
    Previous: 1986 Sea Ray 250 Sundancer. 260 Merc Alpha 1 Gen 1
    5.7 Merc BIII
    Does the power come from the center post on the truck side?
     
  8. dlvwill

    dlvwill Member

    150
    Jun 24, 2011
    Wichita, KS
    2004 220 Select
    350 MAG MPI w/ Bravo III
    Yes, see pin out attached.
     

    Attached Files:

  9. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    PA
    Various
    Various
    I'd have to look myself as it's not something I've committed to memory.

    At this point, it's not that important - check for power on the 5th pin/blue wire and post results.
     
  10. brewster16

    brewster16 Active Member

    386
    Aug 9, 2009
    Long Beach Island, N.J.
    '07 44 Sundancer
    Twin Cummins QSC 8.3
    If your trailer has surge brakes, meaning momentum of braking or accelerating engages or disengages the trailer brakes, then your problem is NOT an electrical function it is a mechanical function. On my surge brake equipped dual axel trailer there is a 4 inch pin that you need to remove from the trailer neck hole and reinsert in a more proximal (different) hole in order to disengage trailer brakes for backing up. Doing so will prevent the surge mechanism from sliding back and engaging your brakes when you back your rig up.
     
    Espos4 likes this.
  11. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    PA
    Various
    Various
    Brewster, disc-braked equipped surge brake trailers use an electrical solenoid to "close off" the fluid supply to the brakes when reverse is applied. By far, the most common reason for "brakes locking up on me in reverse" with this setup is an electrical issue... the number one issue being a failed solenoid. Wiring/corrosion/grounds after that.
     
  12. Woody

    Woody Well-Known Member PLATINUM Sponsor

    Nov 20, 2007
    N. Wisconsin/Lk Superior
    2005 420DA
    Cummins 6CTA8.3
    Why not test each post on the truck side? See what they do. In the process you'll find out if any go hot when truck is put in reverse. Maybe look at the back side of that plug, is the center post even wired on your truck?

    It doesn't sound like this is your problem but sometimes on my trailer this will happen to me....I'll apply brakes and stop, put truck in reverse and brakes will be applied to some degree. I've learned to slightly pull ahead again taking pressure off the surge brakes then start backing. If you shift into reverse while system still has pressure from the stop you are actually locking them on.
     
  13. ENstig8or

    ENstig8or Active Member GOLD Sponsor

    101
    Jun 4, 2013
    New Jersey
    2003 Sea Ray 450 Express Bridge.....

    2016 Sea Ray 21 SPX BR
    Cummins 480CE (450)
    Mercruiser 4.3L (21 SPX)
    This is exactly how mine works. I ran into the same issue. It turned out to be the adapter I was using. It didn't support the pin needed for the brakes to be disengaged. I ended up buying this adapter and that took care of it. https://www.amazon.com/gp/product/B0049MTHTA/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1
     
  14. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    PA
    Various
    Various
    That's strange that you had a 7 to 5 adapter that didn't support the proper pin. Really weird. I use a ton of these things (between personal use and selling them) and have never found one that 'purposefully' didn't support that function. Maybe it was defective? But, either way, I guess it is what it is. The one you ended up with is nice since it has the lights to tell you if a function isn't working... which does occasionally happen on the truck side (although rare).
     
  15. ENstig8or

    ENstig8or Active Member GOLD Sponsor

    101
    Jun 4, 2013
    New Jersey
    2003 Sea Ray 450 Express Bridge.....

    2016 Sea Ray 21 SPX BR
    Cummins 480CE (450)
    Mercruiser 4.3L (21 SPX)
    You are probably correct. It could have quite possibly been defective. I happened to borrow my friends adapter and it worked, so I ordered the one I linked to previously and the mystery was solved.
     
  16. boatman37

    boatman37 Well-Known Member

    Jun 6, 2015
    pittsburgh
    2006 Crownline 250CR. 5.7 Merc BIII
    Previous: 1986 Sea Ray 250 Sundancer. 260 Merc Alpha 1 Gen 1
    5.7 Merc BIII
    Mine is the same adapter I used with my last truck so unless it went bad then it is good....lol. But I still have to test it after replacing the fuse. I do have power to the center post now since replacing the fuse.
     
  17. Leardriver

    Leardriver Member

    168
    May 24, 2016
    Denver, CO
    2004 270 Sundeck 8.1 Bravo III
    5.0, 5.7, 6.2 8.1 Bravo III over the years
    I back up with my truck, with a working blue wire, as far as I can into the barn, but then I use a skid steer to tuck the boat into the corner. It is a royal pain to continually have my great working 4 discs grab every chance they get. I have to really creep slowly.
     
  18. boatman37

    boatman37 Well-Known Member

    Jun 6, 2015
    pittsburgh
    2006 Crownline 250CR. 5.7 Merc BIII
    Previous: 1986 Sea Ray 250 Sundancer. 260 Merc Alpha 1 Gen 1
    5.7 Merc BIII
    Mine is fixed. It was the blue wire that activates the solenoid on the trailer that shuts down the trailer brakes. Venture decided it was a good idea to pinch the wire between the fender washer and frame rail on the safety chain through bolt.
     
    techmitch likes this.
  19. TimW

    TimW New Member

    8
    Jul 2, 2018
    2003 260 Sundancer
    350 MAG MPI
    Tri-axle venture trailer
    F250 diesel truck
    350 MAG MPI
    +100 and I back boat trailers up for a living at my campground
     
  20. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    PA
    Various
    Various
    Up above, we talked about a mechanical lockout that most trailers have, should the solenoid fail. Check your coupler - there is usually a way to do that... whether a steel pin or a piece of 2x4 (or similar) placed in a notched cutout.
     

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