Trailer Braking System Difference When Connected to a Coach with Air Brake System

Question:

Ive read all the recommendation for the air braked motor coach to electric brakes on a trailer. Id like to back up a step: What trailer brake set up would be a better purchase to use with a motor coach with air brakes given a choice. How is the trailer braking applied with consideration for the engine brake is being used.

asked by: Greg

Expert Reply:

This is an excellent question. I reached out to some manufacturers and their tech's didn't know, so I did a little more research to help.

For an air brake motor coach, when you hit the engine brake or jake brake the engine slows the vehicle by opening exhaust valves in your cylinders while at the top of the compression stroke versus using the air brake system to slow the vehicle using the air brake system. The brake lights still need to light in most states because you are decelerating, and that is where the trailer brake systems will differ.

If you are using an electric brake controller like the Prodigy P3 # 90195, then the inertia sensor integrated in the proportional controllers will sense that deceleration and apply the trailer brakes. It will see the brake light signal and use the sensor to proportionally apply the trailer brakes.

If you are using an air over electric controller like the Hayes Air Actuated Trailer Brake Controller - 1 to 4 Axles - Proportional # HA100400C then they sense the braking pressure based on the air pressure when you hit the brake pedal, but they don't apply the brakes to your trailer when using the engine brake because your brake pedal in your coach isn't being applied so it doesn't see the difference in air pressure to apply the brakes to the trailer.

expert reply by: Jason S