How to Test Trailer Brakes with a Multimeter (Three-Step Guide)

Faulty or worn trailer brake magnets can cause serious problems with stopping the trailer instantly. Some problems can be noticed just by looking at your brake magnets, but sometimes there can be certain electrical problems that affect your trailer's brakes.

A faulty brake magnet can cause the brakes to slack or surge or cause the brakes to pull to one side. This is a good enough reason to understand how your braking system works and how to fix it if the need arises. The most important step in understanding how trailer brakes work is learning how to test trailer brakes with a multimeter.

In general, if you want to test your trailer brakes with a multimeter, you need to:

(1) Remove the brake magnets

(2) Place the brake magnet base on the negative terminal.

(3) Connect the positive and negative wires.

Below I will explain this three-step guide in detail.

Understanding how the braking system works

There are two main types of trailer braking system: impulse trailer brakes and electric trailer brakes. Before you go for the test, you need to know what type of braking system your car has. Below I will talk about two types of braking systems. (1)

• The first type is trailer impulse brakes, which contain an impulse clutch mounted on the trailer tongue. In this type of trailer brake, the braking is automatic, which means that there is no need for an electrical connection between the tractor and the trailer, except for the headlights. Inside there is a connection to the main hydraulic cylinder. The forward momentum of the trailer acts on the surge protection clutch whenever the tractor applies the brakes. This causes the car to move backwards and put treat on the master cylinder piston rod.
• The second type of brake system is the trailer's electric brakes, which are actuated by an electrical connection to the brake pedal or a variable inertia switch mounted on the trailer's dashboard. Whenever the trailer's electric brakes are applied, an electrical current proportional to the rate of deceleration energizes a magnet inside each brake. This magnet actuates a lever that, when activated, applies the brakes. This type of controller can be configured for different trailer loads.

How to test trailer brakes with a multimeter

If you want to measure your trailer brakes with a multimeter, you need to follow 3 specific steps, which are:

1. The first step is to remove the brake magnets from the trailer.
2. The second step is to place the base of the brake magnet to the negative terminal of the battery.
3. The last step is to connect the positive and negative leads of the multimeter to the battery. You should connect a multimeter to the blue wire going to the back of the brake controller and if you notice any current on the multimeter then the brake magnet is dead and needs to be replaced.

I would recommend that you use a 12 volt battery when checking the brake system and you should connect the blue wire that controls the brakes to a multimeter and set it to the ammeter setting. You should get the maximum amp reading below.

Brake diameter 10-12

• 5-8.2 amperes with 2 brakes
• 0-16.3 amperes with 4 brakes
• 6-24.5 amperes use with 6 brakes

Brake diameter 7

• 3-6.8 amperes with 2 brakes
• 6-13.7 amperes with 4 brakes
• 0-20.6 amperes use with 6 brakes

I also advise you to use the ohmmeter feature on your multimeter to check the resistance of your brake magnet.

There is a certain range that you should notice on your brake magnets and that range should be between 3 ohms and 4 ohms depending on the size of your brake magnets, if the result is not like this then the brake magnet is damaged and will have to be replaced. (2)

When checking your trailer's brakes, there are electrical problems that can affect how your brakes work, and you can do a visual inspection to determine where the fault is in your brake system.

Visual inspection requires three steps to determine if there is a problem.

1. The first step is to check the trailer brake center for signs of any kind of coil. If you find it, it means that it is worn out and needs to be replaced quickly.
2. The second step is to take a ruler which you will lay across the top of the magnet. This edge should be parallel to the straight edge all the way, and if you notice any change or gouge in the surface of the magnet, this is indicative of abnormal wear and should be replaced immediately.
3. The last step is to check the magnet for grease or oil residue.

Symptoms of a bad trailer brake

There are certain issues you should be aware of if you don't like testing trailer brakes. These issues indicate that you most certainly have a brake problem and you should have your trailer's brakes checked immediately to confirm. Here are some of these problems:

• One such problem is a weak front electric brake, especially if you have electric brakes on the four wheels of your trailer. In a situation where everything is working perfectly, the round part of the brake actuating lever must point forward in order for the trailer brakes to work properly.
• Another problem arises when you notice that your trailer is somehow pulling to the side when you apply the brakes. This indicates that your trailer's braking is out of balance.
• Another major problem is if you notice that your trailer's brakes lock up towards the end of a stop. When you come to a stop and your brake locks up, the problem is with the brake control unit settings. Most likely, the resistance of the brakes is too high, which will lead to rupture and wear of the brake pads.

You can check here how to test trailer lights with a multimeter.

Summing up

It should always be remembered that trailer brakes need frequent regular maintenance due to the heavy loads carried by these vehicles, so I would advise you to always check your trailer brakes to avoid any crashes or accidents on the road due to improper braking. systems.

Problems with short circuits in the wiring also lead to serious problems. Worn or damaged wires can result from placing the wire inside the axle itself.

If you see a message on the brake controller screen saying "output shorted", you should start looking for wiring problems inside your axle. You should also be extremely careful when working with wires and electricity to prevent electric shock.

Other useful tutorials that you can view or bookmark are listed below;

• How to check the battery with a multimeter
• How to measure amps with a multimeter
• How to Use a Cen-Tech Digital Multimeter to Check Voltage

Recommendations

(1) braking system - https://www.sciencedirect.com/topics/

engineering / braking system

(2) magnet - https://www.britannica.com/science/magnet