Help with electric brakes

Discussion in 'General RVing' started by MarshalMac, Aug 15, 2005.

  1. MarshalMac

    MarshalMac New Member

    I have what I believe is a 1970 Holiday Rambler Vacationer, and it has brakes on all four wheels. I have no idea how these work. They appear to have magnets on the wheels that rub against the drums. Is that correct? How does it work?

    The brakes shoes appear to be in good shape (look fairly new in fact although old). There is also an adjuster on there (they are pretty tight, hard time getting drums on/off to repack bearings).

    Right now the brakes do not work, do they need a battery? There is a battery mounted to the trailer but it does not work (broken post). There is also what appears to be an emergency stop cable that someone has cut off or is broken going to a small box on the tongue.

    Any help greatly appreciated! Thanks again.
     
  2. Kirk

    Kirk Senior Member

    Help with electric brakes

    Trailer brakes are electric and they receive power from the tow vehicle. You must have a brake control installed in the tow vehicle that is actuated by the tow vehicle's brake pedal. It then sends power to the coils of the trailer brake system to apply the brake at a voltage that varies with the amount of break pedal movement in the tow vehicle. Some trailers also have a "brake away" switch on the tongue of the trailer that will apply the trailer brakes from the trailer's battery if it comes loose from the tow vehicle. You can test the brake by applying 12V-dc power to the coils.
     
  3. MarshalMac

    MarshalMac New Member

    Help with electric brakes

    I really appreciate the reply, Kirk, thanks!

    Trailer was hooked up to tow vehicle with controller, nothing. Maybe the battery has to be hooked up and fully charged? Also maybe the breakaway cable also must be hooked up and working? I'm not sure.

    Also, what are the "magnet looking things" on the inside of wheels, and how do they work and what do they do?

    Anyway, thanks again, I'm still working on it!!!
     
  4. C Nash

    C Nash Senior Member

    Help with electric brakes

    MarshalMac, You need a volt meter or test light (12volt). As Kirk said the tow vehicle supplies the voltage via the controller. Check at the wires at the drum to see if you have voltage when the controller is applied. The breakaway does not have to be hooked up. It's there for safety and you will want it working before towing. The magnet looking things are magnets. When voltage is applied through the windings it creates a magnet that applies the brakes. They could be bad but not likely that all four are gone. If it has sat with the breakaway pulled to lock the brakes all may be bad. The rv also must have a good ground back to the tow vehicle to work. Do all lights work properly ?(running light, tail lights) good luck :)
     
  5. MarshalMac

    MarshalMac New Member

    Help with electric brakes

    Thanks C Nash for reply. Lights seem to work fine, need a few of the clearance lights replaced, but other than that they work. I'll get on it this week and try to test it all out. Thanks again!!
     
  6. Kirk

    Kirk Senior Member

    Help with electric brakes

    You may want to make a jumper that will allow you to supply a 12V source directly to the lead in the trailer power plug that goes to the brakes. Without that, you will need some way to have the brake pedal applied to send power to the trailer's brake system. If you do make up such a jumper, be sure that you also put a fuse in the jumper just to protect the wire harness in the event of a short. I would look to see what size the fuse is that supplies your brake controller and use that same size. By doing that you can supply a constant brake signal that will allow you to trouble shoot with a meter. But before you do that, take the meter and read from the brake pin of the plug to ground to be sure that there is no direct short (0 ohms). Then you may want to measure the resistance from the plug to each wheel to see what that is. It should be near 0 ohms if you measure to where the lead connects to the brake windings. That would indicate the wires are good.
     

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