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  1. #1
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    Trailer Brake Lockup While Driving 55 MPH

    2018 GD 310GK (Solitude). 2020 Chevy Silverado 3500. Using OEM brake controller. While driving approx. 55 mph and without touching brake pedal the trailer brakes locked up briefly (1 second or less). Caused a skid of 8 feet and threw a bunch of smoke. When we pulled over to investigate, the trailer brakes did not work.

    Turned off truck, pulled and reinstalled 7-pin umbilical. Wiggled it around a bit. Started truck and noticed a diagnostic message saying traile brake connection was inoperative. Turned off truck, pulled and reinstalled umbilical and now truck diagnostic status reports brake connection is good.

    Drove slowly to camp site, brakes working fine. Tried to measure voltages while pressing brake pedal and/or brake controller without much success, as discussed in other posts (due to complexities of ABS and whatnot). Will try again with trailer plugged in if I have a second 7-pin connector on bumper.

    Inspected wires at each brake but did not observe any issues. When brake is applied I can hear buzzing from brakes. Inspected back side of truck bed 7-pin connector and it appears ok.

    Inspected connections where trailer umbilical connects to trailer in junction box. All looks good.

    The behavior of the lockup is similar to what would happen if the breakaway switch had activated. Inspection of these connections looks good and the plunger is intact. I've never tested this circuit as recommended elsewhere in these forums.

    Wondering if this is the most likely culprit. Should I replace it? Have to drive home in a couple days (200 miles) so looking for quick responses.

    Thanks.

  2. #2
    Site Team Soundsailor's Avatar
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    Quote Originally Posted by ino1thing View Post
    2018 GD 310GK (Solitude). 2020 Chevy Silverado 3500. Using OEM brake controller. While driving approx. 55 mph and without touching brake pedal the trailer brakes locked up briefly (1 second or less). Caused a skid of 8 feet and threw a bunch of smoke. When we pulled over to investigate, the trailer brakes did not work.

    Turned off truck, pulled and reinstalled 7-pin umbilical. Wiggled it around a bit. Started truck and noticed a diagnostic message saying traile brake connection was inoperative. Turned off truck, pulled and reinstalled umbilical and now truck diagnostic status reports brake connection is good.

    Drove slowly to camp site, brakes working fine. Tried to measure voltages while pressing brake pedal and/or brake controller without much success, as discussed in other posts (due to complexities of ABS and whatnot). Will try again with trailer plugged in if I have a second 7-pin connector on bumper.

    Inspected wires at each brake but did not observe any issues. When brake is applied I can hear buzzing from brakes. Inspected back side of truck bed 7-pin connector and it appears ok.

    Inspected connections where trailer umbilical connects to trailer in junction box. All looks good.

    The behavior of the lockup is similar to what would happen if the breakaway switch had activated. Inspection of these connections looks good and the plunger is intact. I've never tested this circuit as recommended elsewhere in these forums.

    Wondering if this is the most likely culprit. Should I replace it? Have to drive home in a couple days (200 miles) so looking for quick responses.

    Thanks.
    My initial thought after reading your title was the controller. After reading the whole post it also seems reasonable that you have a partially stripped wire causing the brake lock up. A few folks on the forum have found worn wires, could that be your culprit?
    Stephen and Judy
    2022 Reflection 150 Series 260RD (Stella)
    2017 Chevy Silverado 2500 HD (Blue)
    Traded - 2018 Forest River Rockwood Minilite 2104S

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    Thanks for the quick response Soundsailor! If there are any stripped or exposed wires, they are not visible in the areas I've inspected. Perhaps inside drum somewhere. Might explain intermittent nature of the truck's diagnostics.

    Hope it's not the OEM controller.

    So, if a stripped wire in that circuit goes to ground, will that activate all 4 brakes?

  4. #4
    Seasoned Camper finz04's Avatar
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    Check your emergency breakaway switch as well. Perhaps there is an intermitent short. That would lock up the brakes.
    Mike C.

    2023 GD Imagine AIM 15RB - 2022 Chevy Silverado 2500HD Custom, 6.6 liter gas, 69 bed with Puck System, Blue Ox SwayPro

  5. #5
    Rolling Along
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    Pull the pin on the emergency switch, check that it works, and look inside it. On my last trailer, on one of my does it work, it did not. I inspected it and found it to be fried internally. Not sure how that happened, but was simple to replace the switch.

    I am not sure how, but maybe the contacts or wires could have momentarily shorted?
    2023 Chevy 3500HD CC SB 4x4 Dmax
    2021 GD 320G with 8K axles

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    If it isn't something do to with the emergency switch, then you might pull the tires and hubs. I had random troubles (not exactly like your situation) but did not find the issue until I did hub maintenance. Once I had eyes on the brake assemblies I found a wire had pinched, worn the insulation off, and was shorting against a spindle. If you have exhausted all other potential problems, might be a place to check. Otherwise, you may need to follow the wires and check for shorts.
    Chad
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    We do not have cell service at camp site, so my responses will be sporadic at best. Really appreciate all the assistance.

    I replaced the breakaway switch and busted the old one open to inspect. It looks fine. Very simple operation. Not much to go wrong inside.

    Guess I'll have to try some of the other ideas when I get home.

  8. #8
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    Quote Originally Posted by ino1thing View Post
    Thanks for the quick response Soundsailor! If there are any stripped or exposed wires, they are not visible in the areas I've inspected. Perhaps inside drum somewhere. Might explain intermittent nature of the truck's diagnostics.

    Hope it's not the OEM controller.

    So, if a stripped wire in that circuit goes to ground, will that activate all 4 brakes?
    The brake wires run through the axles. We had an issue with the brakes disconnecting and reconnecting while driving. (But not locking up). Dealership replaced the wiring, this time zip tied to the outside of the axles. Service manager showed me the old wires. Very brittle and frayed. No issues since.
    2018 Solitude 384 GK-R
    2017 GMC 3500 HD Denali

  9. #9
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    Quote Originally Posted by wannabervin View Post
    The brake wires run through the axles. We had an issue with the brakes disconnecting and reconnecting while driving. (But not locking up). Dealership replaced the wiring, this time zip tied to the outside of the axles. Service manager showed me the old wires. Very brittle and frayed. No issues since.
    Thanks for the feedback wannabervin. I've read similar stories elsewhere. We had another occurrence of lockup on the way home AFTER I disconnected the OEM brake controller by cutting the brake wire in the 7-pin pig tail at the trailer junction box and verifying with multimeter that there was no voltage going to trailer brake wire when brakes applied in truck. I had to pull over and after much consideration, I cut the brake wires at the driver's side hubs (since we had already decided to drive home without trailer brakes and simply relying upon engine brake, exhaust brake and truck foot brake.

    After getting home safely, I disassembled a couple hubs to inspect for wiring damage and found none. I cannot figure out where the voltage to activate the brakes is coming from, so I ended up taking it into a service shop. After describing the whole story to their head mechanic, he could not come up with anything either, but he agreed to keep the trailer and troubleshoot further using his own truck. His first thought was the OEM brake controller went rogue, but then he verified I cut the correct wire so now he needs to think a bit harder.

  10. #10
    Site Sponsor Steven@147's Avatar
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    Quote Originally Posted by ino1thing View Post
    Thanks for the feedback wannabervin. I've read similar stories elsewhere. We had another occurrence of lockup on the way home AFTER I disconnected the OEM brake controller by cutting the brake wire in the 7-pin pig tail at the trailer junction box and verifying with multimeter that there was no voltage going to trailer brake wire when brakes applied in truck. I had to pull over and after much consideration, I cut the brake wires at the driver's side hubs (since we had already decided to drive home without trailer brakes and simply relying upon engine brake, exhaust brake and truck foot brake.

    After getting home safely, I disassembled a couple hubs to inspect for wiring damage and found none. I cannot figure out where the voltage to activate the brakes is coming from, so I ended up taking it into a service shop. After describing the whole story to their head mechanic, he could not come up with anything either, but he agreed to keep the trailer and troubleshoot further using his own truck. His first thought was the OEM brake controller went rogue, but then he verified I cut the correct wire so now he needs to think a bit harder.
    My thoughts, normally power to actuate the RV brakes only comes from two independent sources. Pin 2 of the 7 way being fed from your trucks brake controller. Or RV battery power direct to the RV brakes through the brake away switch.

    If you have a brake wire in the RV hard shorted to ground your truck should sense this and disconnect further braking action. In this case you should get a "Trailer Brake Disconnect" message from your truck. In the case of an intermittent brake wire short to ground you may get a "Check Trailer Brake Wiring" message from your truck. I think GM, Ford and Ram all send a short brake pulse through pin 2 of the 7 way connector to the RV to make sure the brakes are still connected.

    Now if you cut the pin 2 wire of the 7 way, that should kill that brake power source. And if you replaced the brake away switch that should eliminate that possibility. Now this is an RV Without ABS.

    From what I hear all new drum brake RVs coming from GD all have ABS. This puts a whole new wrinkle in RV braking action. I do not know for sure how the manufacturer installs the RV ABS system or how its powered. But I would check out the RV ABS controller to make sure it is not randomly sending out power to the RV brakes. If you can find the ABS controller, disconnect the power feed into it, should be just a plug and see if your problem goes away, Admittingly if you disconnect the ABS controller there probably will not be any brakes on the RV but I don't know exactly how these RV ABS systems work.

    Here's a diagram I found of Lipperts RV ABS system, yours should be similar. I would suspect the RVs ABS controller,
    Attached Thumbnails Attached Thumbnails Lippert ABS.pdf  
    Steve & Tami Cass - Fulltimers since July 2020, Escapee's, FMCA Members
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