Help me fix my trailer brakes! - Pirate4x4.Com : 4x4 and Off-Road Forum

Blair · 09-12-2002, 02:37 PM

I just bought a used wells cargo 16 foot cargo trailer for work. Its tows great works awesome except the brakes don't work. Which is fine for now but will suck in the winter. I have never worked on electric brakes before and hardly know where to start. When the controller feeds power to the trailer brakes I have power at all 4 wheels as tested on the wires going into the baching plate. Nothing happens though no noise etc. If anyone can tell me what to look for when I pull the drums off I would appreciate it very much

Tusker · 09-12-2002, 05:31 PM

How many volts are you getting at the brakes? If they are really not working (and therefore not drawing any current), you should get between 12 and 13 volts. If they are working, you will get between 3 and 10 volts, depending on number of brakes, wire size, etc. If I understand electric brakes (I have worked on them some but ain't sure about the details), the "magnet" in them is more like a resistor, which consumes energy, creates a magnetic field as current flows through it, which causes the "magnet" to become magnetized and attracts it to the drum, where it tries to stick and creates leverage to operate the shoes.

I would bet that you have an open circuit (i.e. bad no ground). Check the resistence on the ground wire. Should be "zero" resitance. If it isn't, that is your problem.

FYRMAN · 09-12-2002, 06:33 PM

cut the wires and stick an ohm meter on them. Should be around 20. If you get nothin... bad magnets. You can also pull the drum and see if a screwdriver sticks to the magnet. you should be able to pull out on one end of the screwdriver and pull it off, but if you pull straight off the magnet, it should be a bitch.

you can also climb under the trailer, with one side in the air, and wiggle the connections while someone activates the brake controller. You probably would get someting then.

You can also snap in a new ground, like was mentioned before.

Blair · 09-12-2002, 09:06 PM

I didn't have the digital multimeter out when I checked the current before so I will need to check that. Also do the brakes generally ground to the frame and then into the trailer plug or do they run a wire the whole way? Thanks for the help guys!

smurfsdad · 09-12-2002, 09:19 PM

Ground wire the whole way is the only way to go.

FYRMAN · 09-12-2002, 09:21 PM

Two prongs on the plug are indeed used. One is the ground wire. It should go to a good chassis ground somewhere close to the tongue. The second wire is the brake wire. It runs from the plug, through whatever harness/conduit/split loom to one of the wires on the magnet. The current energizes the magnet, the runs out of the other wire to a ground, usually right close to the frame behind the backing plate. Some manufactures do run a double set of wires, but the ground just travels to where ever they grounded to the chassis anyways. If you wanna double up on the ground, or for whatever other reason, you can splice into the ground wire with a 3M (aka Schotch Lock) connector, and then run a shortwire to a ring connector, then shoot a self tapping screw through the ring connector to the frame.

09-12-2002, 02:37 PM	#1 (permalink)
Blair Registered User Join Date: Sep 2001 Member # 7069 Location: Twin Falls ID Posts: 236	Help me fix my trailer brakes! I just bought a used wells cargo 16 foot cargo trailer for work. Its tows great works awesome except the brakes don't work. Which is fine for now but will suck in the winter. I have never worked on electric brakes before and hardly know where to start. When the controller feeds power to the trailer brakes I have power at all 4 wheels as tested on the wires going into the baching plate. Nothing happens though no noise etc. If anyone can tell me what to look for when I pull the drums off I would appreciate it very much __________________ More power!

09-12-2002, 05:31 PM	#2 (permalink)
Tusker Registered User Join Date: Jan 2001 Member # 2752 Location: Fairfield, CA Posts: 2,043	How many volts are you getting at the brakes? If they are really not working (and therefore not drawing any current), you should get between 12 and 13 volts. If they are working, you will get between 3 and 10 volts, depending on number of brakes, wire size, etc. If I understand electric brakes (I have worked on them some but ain't sure about the details), the "magnet" in them is more like a resistor, which consumes energy, creates a magnetic field as current flows through it, which causes the "magnet" to become magnetized and attracts it to the drum, where it tries to stick and creates leverage to operate the shoes. I would bet that you have an open circuit (i.e. bad no ground). Check the resistence on the ground wire. Should be "zero" resitance. If it isn't, that is your problem. __________________ 86 Samurai w/gun rack, 92" WB, VW 1.9 TD, Toyota 5-speed and dual cases with 4.7 gearset, Toyota axles with Longfields, 5.29's, ARB's f&r, YJ's, 35's, FJ-60 power steering, high steer, ............. <>< <>< <>< Hey, if this rig is for wheelin', what are all these animal parts doin' in here?

09-12-2002, 06:33 PM	#3 (permalink)
FYRMAN Registered User Join Date: Apr 2001 Member # 4358 Location: otHELLo, Washington Posts: 3,700	cut the wires and stick an ohm meter on them. Should be around 20. If you get nothin... bad magnets. You can also pull the drum and see if a screwdriver sticks to the magnet. you should be able to pull out on one end of the screwdriver and pull it off, but if you pull straight off the magnet, it should be a bitch. you can also climb under the trailer, with one side in the air, and wiggle the connections while someone activates the brake controller. You probably would get someting then. You can also snap in a new ground, like was mentioned before. __________________ [COLOR="Red"]Central Washington Muff Dive and Rescue Team[/COLOR] Last edited by FYRMAN; 09-12-2002 at 06:34 PM.

09-12-2002, 09:06 PM	#4 (permalink)
Blair Registered User Join Date: Sep 2001 Member # 7069 Location: Twin Falls ID Posts: 236	I didn't have the digital multimeter out when I checked the current before so I will need to check that. Also do the brakes generally ground to the frame and then into the trailer plug or do they run a wire the whole way? Thanks for the help guys! __________________ More power!

09-12-2002, 09:19 PM	#5 (permalink)
smurfsdad Registered User Join Date: Mar 2000 Member # 324 Location: Nevada Posts: 4,005	Ground wire the whole way is the only way to go. __________________ Family, Friends, riders and racers, its who we are.

09-12-2002, 09:21 PM	#6 (permalink)
FYRMAN Registered User Join Date: Apr 2001 Member # 4358 Location: otHELLo, Washington Posts: 3,700	Two prongs on the plug are indeed used. One is the ground wire. It should go to a good chassis ground somewhere close to the tongue. The second wire is the brake wire. It runs from the plug, through whatever harness/conduit/split loom to one of the wires on the magnet. The current energizes the magnet, the runs out of the other wire to a ground, usually right close to the frame behind the backing plate. Some manufactures do run a double set of wires, but the ground just travels to where ever they grounded to the chassis anyways. If you wanna double up on the ground, or for whatever other reason, you can splice into the ground wire with a 3M (aka Schotch Lock) connector, and then run a shortwire to a ring connector, then shoot a self tapping screw through the ring connector to the frame. __________________ [COLOR="Red"]Central Washington Muff Dive and Rescue Team[/COLOR]

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