How to Release Trailer Air Brakes Manually

The first thing you need to do is familiarize yourself with the trailer air brake system. Before you even attempt to release the trailer brakes, take time to look at and understand the emergency switch, which is typically located in the cab of your truck just below or above the dashboard.

Once you are familiar with all of these components, it’s time to learn where and how to release your trailer air brakes manually. To begin, locate the trailer air brake control handle and make sure that it’s in the “brake off” position. If this handle is not in this position, then your trailer brakes will not be released until you put it there. Now that you have confirmed that your handle is in its proper place, push down on your dash valve control knob and hold it for at least five seconds; this will allow air pressure into both of your service lines (the blue line controls all four wheels while the red line operates only two).

This brings us to our next step: pulling on both of your service lines until they reach a point where they offer resistance (if you feel no resistance when pulling on either one of these lines then that means one or both are damaged and need repaired as soon as possible).

Step 2

Before proceeding, you will want to make sure that the parking brake on your tractor is set. You’ll also need to push in the red push button on top of the air tank.

Step 3

  • Locate the emergency air release valve on the trailer, which is usually a yellow button on top of a yellow cap. Push the button to release any remaining air that may still be in the system.

While pushing the button, check your air pressure gauge to see when there is no remaining pressure (when it reaches zero).

Step 4

Make sure that the tractor’s air compressor is charged, and then release the parking brake on the tractor.

With a suitable assistant to help you, check that all of the trailer’s lights are working. Check that both sides of any fifth wheel couplings are secure. Check that all chocks have been removed from around the tractor’s wheels and that there are no obstructions anywhere in or around your vehicle. Have your assistant check behind the vehicle and make sure it is safe to pull out.

The best way to release trailer air brakes manually is by slowly pulling the trailer air brake control handle toward you.

The best way to release trailer air brakes manually is by slowly pulling the trailer air brake control handle toward you.

You should then hear a faint hissing noise coming from the back of your truck signaling that the trailer brakes are being released. For this to work, you need to make sure that the parking brake lever in your truck is fully down. If it is not down, it will be very hard for you to pull out the trailer air brake control handle.

Steven Hatman
Steven Hatman

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