Trailer Troubleshooting
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Post Fiend
Joined: Oct 2005
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From: Plano TX and Brentwood TN
Trailer Troubleshooting
Technically speaking this isn't a truck tech discussion, although it doesn't really apply to general garage and workshop either, but I don't know where else to post it. Does anybody know if there are manuals, websites or something that I can look at to get a wiring diagram and discussion on how to trouble shoot trailer brakes(either 2 or 4 systems)? I'm checking for a short as my tow command system won't work if it senses problems. I have checked using an ohm meter and the only time I don't get a read is on the brakes, I jump the brake wires at the trailer plug and test the line on the end that attaches to the brakes themselves and I get a signal, so it is something to do with the brakes and I don't know enough about troubleshooting them in order to determine what is wrong. Any thoughts, suggestions, ideas? Thanks.
Postmaster
Joined: Aug 2004
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From: Greenvile, SC
Senior User
Joined: Apr 2005
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Normally, electric brake problems usually end up being problems with the grounds. Had similar problem with a travel trailer and the dealer couldn't find the problem.
I traced all the wires and redid all the grounds. It ended up being the main ground for the whole trailer. It looked good until you separated all the wires. I clean the corosion(sp?) and reassembled. Problem solved.
I traced all the wires and redid all the grounds. It ended up being the main ground for the whole trailer. It looked good until you separated all the wires. I clean the corosion(sp?) and reassembled. Problem solved.
CO River Rat
Joined: Feb 2004
Posts: 3,209
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From: Lake Havasu City AZ
Tex -
This is from Champion Trailer's website; hope it helps:
"TROUBLE SHOOTING ELECTRIC BRAKES
Hydraulic surge brakes are a totally trailer self contained braking system, and therefore all trouble shooting analysis can be concentrated on the trailer to resolve braking problems. However, with electric brakes, both the trailer and tow vehicle contain components integral to the overall electric brake package and therefore trouble shooting the electric brake system can be more complex.
The mechanical operation of electric brakes is fairly simple, if power is available to the magnets, and the magnets are functional. Therefore, we will assume that mechanical problems such as
brakes being out of adjustment
worn shoes
broken springs
worn hub drums, etc.
will be self evident and easily identified for correction.
The majority of problems that occur with electric brakes can be traced to an electrical system problem, and we will concentrate our attention there.
A 12 VDC VOLTAGE TESTER, VOLTMETER, OR TEST LIGHT PIGTAIL WILL BE NEEDED FOR ELECTRICAL SYSTEM TEST.
First, it is essential to isolate the problem area.
TROUBLE SHOOTING TRAILER SIDE
(Question) Is the problem in the trailer or tow vehicle electrical components?
(Answer) Unplug the trailer from the tow vehicle and use a 12 VDC battery with a fuse or circuit breaker, for short circuit protection, to apply full 12 VDC to the pins of the trailer connector connected to the wires going to the wheel magnets. As you connect the 12 VDC source, you should hear a notable click as the magnets are energized and pulled to the flat drum surface. Another method of testing brake magnet operation is to place a compass near the hubdrum.
If, for example, you had brakes on both axles of a tandem trailer, you should go to each hub drum and assure that each brake cluster magnet is operating. If you could hear brake magnet activation on 1 axle and not the other, you may well have a bad wiring connection on the trailer wiring harness.
Conversely, you may hear 3 magnets click but not # 4. Closer inspection may indicate a bad magnet or a bad wire connection at that magnet.
CAUTION: If a short circuit exists in the trailer electrical system, you could receive burns from melting electrical components if you do not use a fuse or circuit breaker for over current protection when connecting the test battery.
If all magnets click aggressively, the trailer electrical system should be in order, if the wire size is large enough to handle voltage drop. NOTE: Be sure that the brake magnet (-) negative wire is the same size as the positive (+) wire and be sure not to connect the negative (-) return wire to the brake backing plate or trailer frame.
The negative must return thru the trailer plug and connect to the tow vehicle negative for optimum system performance. It is also essential that brakes be PARALLEL WIRED not series wired.
TROUBLE SHOOTING TOW VEHICLE SIDE
Now that you've completed tests and repairs on the trailer side of the electric brake package, we can move to the tow vehicle. It is important to note that many times loose connections are responsible for more electric brake problems than any other single item. A loose connection creates a resistance to current flow. As current draw increases, this point of resistance heats up. As a conductor heats up, it becomes more resistant to current flow. And without proper current flow, the magnets do not pull themselves to the flat hub drum surface, and the brakes therefore do not operate proportionally to the controller output signal. Many times the trailer plug connector, attaching the trailer to the tow vehicle electrical system is the loose connection source.
Dash mounted brake controllers, both inertial deceleration type, and power adjust only type, are the controllers most commonly used. They both take brake light (on) sensing signal as the primary control input and if this input is positive (on), the power amplifier in the controller is biased (turned on), at which time, depending on power adjust set point, and/or brake sensing pendulum position, a proportional amplifier power output is sent to the brake magnets.
To test output from the controller, use a voltmeter reading 12VDC at mid scale. Some controllers will not give satisfactory readings with an RMS voltmeter and you will need to use a standard 12 volt bulb pigtail for test.
Testing Battery Input
First test your battery power INPUT tap at the brake controller to assure that you have full 12VDC thru your auto reset circuit breaker and up to the controller.
Testing Manual Over-ride
At the power output tap of the brake controller, connect your voltmeter and operate the MANUAL BYPASS BUTTON on the controller. You should develop full output voltage within 3 or 4 seconds. If you have output voltage here and your brake magnets are not picking up, you should find a loose connection between this point and the previously tested trailer as a problem.
Testing Automatic Operations
On inertial deceleration controllers, set the gain control to it's maximum (aggressive) position, and with power adjust controllers set the output to maximum.
Now with your voltmeter connected to the same power output tap we tested earlier, push the brake pedal down and operate the tow vehicle brake lights. Power output voltage should go to maximum. If it does not, check to be sure that brake light sensing voltage is available at the proper tap of the brake controller.
If you have battery input power available, and you have brake light sensing signal available, but you have no output power, the problem should be internal to the controller and will require repair (contact the manufacturer for recommendations) or replacement".
Steve
This is from Champion Trailer's website; hope it helps:
"TROUBLE SHOOTING ELECTRIC BRAKES
Hydraulic surge brakes are a totally trailer self contained braking system, and therefore all trouble shooting analysis can be concentrated on the trailer to resolve braking problems. However, with electric brakes, both the trailer and tow vehicle contain components integral to the overall electric brake package and therefore trouble shooting the electric brake system can be more complex.
The mechanical operation of electric brakes is fairly simple, if power is available to the magnets, and the magnets are functional. Therefore, we will assume that mechanical problems such as
brakes being out of adjustment
worn shoes
broken springs
worn hub drums, etc.
will be self evident and easily identified for correction.
The majority of problems that occur with electric brakes can be traced to an electrical system problem, and we will concentrate our attention there.
A 12 VDC VOLTAGE TESTER, VOLTMETER, OR TEST LIGHT PIGTAIL WILL BE NEEDED FOR ELECTRICAL SYSTEM TEST.
First, it is essential to isolate the problem area.
TROUBLE SHOOTING TRAILER SIDE
(Question) Is the problem in the trailer or tow vehicle electrical components?
(Answer) Unplug the trailer from the tow vehicle and use a 12 VDC battery with a fuse or circuit breaker, for short circuit protection, to apply full 12 VDC to the pins of the trailer connector connected to the wires going to the wheel magnets. As you connect the 12 VDC source, you should hear a notable click as the magnets are energized and pulled to the flat drum surface. Another method of testing brake magnet operation is to place a compass near the hubdrum.
If, for example, you had brakes on both axles of a tandem trailer, you should go to each hub drum and assure that each brake cluster magnet is operating. If you could hear brake magnet activation on 1 axle and not the other, you may well have a bad wiring connection on the trailer wiring harness.
Conversely, you may hear 3 magnets click but not # 4. Closer inspection may indicate a bad magnet or a bad wire connection at that magnet.
CAUTION: If a short circuit exists in the trailer electrical system, you could receive burns from melting electrical components if you do not use a fuse or circuit breaker for over current protection when connecting the test battery.
If all magnets click aggressively, the trailer electrical system should be in order, if the wire size is large enough to handle voltage drop. NOTE: Be sure that the brake magnet (-) negative wire is the same size as the positive (+) wire and be sure not to connect the negative (-) return wire to the brake backing plate or trailer frame.
The negative must return thru the trailer plug and connect to the tow vehicle negative for optimum system performance. It is also essential that brakes be PARALLEL WIRED not series wired.
TROUBLE SHOOTING TOW VEHICLE SIDE
Now that you've completed tests and repairs on the trailer side of the electric brake package, we can move to the tow vehicle. It is important to note that many times loose connections are responsible for more electric brake problems than any other single item. A loose connection creates a resistance to current flow. As current draw increases, this point of resistance heats up. As a conductor heats up, it becomes more resistant to current flow. And without proper current flow, the magnets do not pull themselves to the flat hub drum surface, and the brakes therefore do not operate proportionally to the controller output signal. Many times the trailer plug connector, attaching the trailer to the tow vehicle electrical system is the loose connection source.
Dash mounted brake controllers, both inertial deceleration type, and power adjust only type, are the controllers most commonly used. They both take brake light (on) sensing signal as the primary control input and if this input is positive (on), the power amplifier in the controller is biased (turned on), at which time, depending on power adjust set point, and/or brake sensing pendulum position, a proportional amplifier power output is sent to the brake magnets.
To test output from the controller, use a voltmeter reading 12VDC at mid scale. Some controllers will not give satisfactory readings with an RMS voltmeter and you will need to use a standard 12 volt bulb pigtail for test.
Testing Battery Input
First test your battery power INPUT tap at the brake controller to assure that you have full 12VDC thru your auto reset circuit breaker and up to the controller.
Testing Manual Over-ride
At the power output tap of the brake controller, connect your voltmeter and operate the MANUAL BYPASS BUTTON on the controller. You should develop full output voltage within 3 or 4 seconds. If you have output voltage here and your brake magnets are not picking up, you should find a loose connection between this point and the previously tested trailer as a problem.
Testing Automatic Operations
On inertial deceleration controllers, set the gain control to it's maximum (aggressive) position, and with power adjust controllers set the output to maximum.
Now with your voltmeter connected to the same power output tap we tested earlier, push the brake pedal down and operate the tow vehicle brake lights. Power output voltage should go to maximum. If it does not, check to be sure that brake light sensing voltage is available at the proper tap of the brake controller.
If you have battery input power available, and you have brake light sensing signal available, but you have no output power, the problem should be internal to the controller and will require repair (contact the manufacturer for recommendations) or replacement".
Steve
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