Ensuring the safety and functionality of your trailer brakes is paramount for a smooth and secure towing experience. When it comes to testing trailer brakes, a multimeter can be a valuable tool for diagnosing issues and making necessary adjustments. In this guide, we’ll explore how to test trailer brakes with a multimeter, providing you with the knowledge and confidence to assess your braking system’s performance.
Whether you’re preparing for a long-haul journey or conducting routine maintenance, understanding how to use a multimeter for this task is a crucial skill for any trailer owner or operator. Faulty or worn-out trailer brake magnets can cause serious problems with the trailer’s ability to stop instantly. Some issues may be identified by just inspecting your brake magnets, but occasionally there may be specific electrical issues that impact how well your trailer brake works.
Each time there is an issue with the magnet or the circuit wire in the trailer brake, issues might arise. For this reason, you should check your trailer brakes regularly if you see any signs of a problem. As a trailer owner, you need to understand how important it is for your brakes to function correctly. Our article shows you how to test trailer brakes with a multimeter.
Signs Of Electric Trailer Brake Problems
The most typical symptoms of a broken trailer brake are erratic brake control behaviour, a seizing adjuster spring, and slack return and hold-down springs.
While applying the brakes, your trailer brakes need to be replaced if you experience noise, tugging, or pedal depression. In extreme situations, your wheels may lock up when you’re moving.
Trailer brakes that lock up can be caused by a malfunctioning brake controller, a poor ground wire, or faulty or shorted cables. With a multimeter, we evaluate the resistance, voltage, and amperage of your trailer brake magnets.
How a Braking System Performs Functions
The braking system of a trailer comes in two types.
- The surge trailer brakes.
- The electric trailer brakes.
The surge Trailer Brakes
The first kind is surge trailer brakes, which have a surge coupler attached to the trailer tongue. This kind of trailer brake operates automatically, thus other than the lights, there is no need for an electrical connection between the tow vehicle and trailer. A connection is there, and within is a hydraulic master cylinder. As the tow vehicle applies its brakes, the trailer’s forward momentum drives on the surge coupler. This moves the car in the direction of the back and exerts pressure on the master cylinder piston rod.
The Electric Trailer Brakes
The second type of braking system is the electric trailer brakes which are brakes activated by an electrical connection to the brake pedal or a trailer-mounted inertia switch that can be adjusted.
When electronic trailer brakes are applied, a magnet within each brake is fueled by an electric current that is proportionate to the rate of deceleration. This magnet activates a lever, and when it does, the brakes are applied. Different trailer loads might be accommodated by this sort of controller.
How to Test Trailer Brakes with a Multimeter
This procedure is only one way to test individual brakes; other ways will also be covered in more detail.
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There are three techniques to check for issues with your brakes:
- Testing resistance between brake wires
- Testing amperage from the brake magnet
- Testing current from the electric brake controller
Testing resistance between brake wires
- Set the Multimeter To The Ohms Setting
Set your multimeter to Ohms, which is often denoted by the Omega symbol ( Ω ) to measure resistance.
- Multimeter probe positions
Your brake magnet cables have no polarity, so you may put your probes wherever you choose.
- Connect probes to battery and magnet wire
The black probe should be put on one of the brake magnet lines, and the red probe should be put on the other wire. Check the multimeter for readings.
- Analyze the Results
There are several specifications for this test that you should write down.
Brake diameter 10-12
- 5 – 8.2 amps with 2 brakes
- 0 – 16.3 amps with 4 brakes
- 6 – 24.5 amps usage with 6 brakes
Brake diameter 7
- 3 – 6.8 amps with 2 brakes
- 6 – 13.7 amps with 4 brakes
- 0 – 20.6 amps usage with 6 brakes
You should expect a measurement of between 3.0 and 3.2 ohms for a 7-inch brake drum and between 3.8 and 4.0 ohms for a 10 to 12-inch drum.
The magnet has to be replaced if the reading from your multimeter falls outside of these parameters as they apply to the size of your braking drum.
For instance, if the multimeter presents “O.L” it means that one of the wires is shorted and the magnet should probably be replaced.
Testing Amperage From Brake Magnet
- Set Multimeter To Ampere Measurement
Set your multimeter to the ammeter setting as a first step. In this case, you want to check for wire breakage or internal exposure.
- Multimeter probe positions
Take note of these positions. Put the negative probe on any of your cables, and the positive probe should be put on the battery’s positive terminal.
The braking magnet is then attached to the negative battery post.
- Analyzing the Findings
If the multimeter displays an ampere measurement, your braking magnet has an internal short and has to be changed.
You won’t receive a reading from your multimeter if the magnet is in good condition.
Testing Current From The Electric Brake Controller
A control panel for electric brakes is used to operate them.
When you press the brake pedal and bring your car to a halt, this panel supplies the magnets with electric current.
Now, if this electronic brake controller is malfunctioning or if insufficient electricity from it is getting to the brakes’ electromagnets, a problem with your brakes will result.
There are four ways to test this gadget.
The trailer brake wire between your brake controller and the brake magnet may be tested using a multimeter.
There are a few things you want to pay attention to while usually evaluating brakes for issues.
You should know how many brakes you have, how your trailer pin plug is set up, and how much suggested current the magnet wires should provide.
Below are the guidelines to follow. This suggested current depends on the size of the magnet.
- Amperes Are Measured With A Multimeter
Set the ammeter settings on the multimeter’s dial.
- Multimeter probe positions
The blue wire coming from your connection plug should be connected to one probe, and the other probe should be connected to a brake magnet wire.
- Take Reading
Using the pedal or electronic control panel, engage the brakes while the engine is running in your automobile (you can have a friend do this for you). Now, you need to gauge how much current is flowing to the brake wires from the connection.
Analyze the Results
Determine if you are receiving the appropriate quantity of current using the aforementioned requirements.
The controller or cables may be defective and require replacement if the current exceeds or falls below your suggested standard.
You might perform further testing to determine the source of the current coming from your electronic brake controller.
Check out this article to learn how milliamps appear on a multimeter in case you notice lower readings while measuring the amperage.
Compass Test
Simply set the compass next to the brakes, provide electric power to the brakes via the controller, and observe to see if it moves or not to do this test.
If the compass isn’t moving, the magnets aren’t receiving current, then your controller or wiring may be malfunctioning.
Final Thoughts
In conclusion, trailer brakes need routine servicing and maintenance much like the brakes on any towing vehicle. Keep in mind that how frequently you tow and the weight of the items you tow determine the recommended servicing frequency.
Simply, you should check your brakes more frequently the more you haul.
Read Also: What Is OL On A Multimeter?
FAQs
What voltage should a trailer braking system have?
The brake/stop light pin is located on pin 6 of a trailer plug. Depending on the towing vehicle, this voltage should be 12V or a little bit more.
What causes poor electric trailer brakes?
Low or no voltage and amperage at the brakes are the most typical electrical issues. Poor electrical connections, open circuits, inadequate wire size, damaged wires, blown fuses (fusing brakes is not advised), dysfunctional controllers, or resistors are common reasons for this situation.
Should electric trailer brakes have continuity?
Should there be continuity between the ground and the 12-volt brake cable? Helpful Expert Reply: Yes, you should have continuity with a multimeter between that and the ground pin when your brake controller is providing power back to your 7-Way connector.