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RV Brake System Air Dryer Filter Replacement

Changing the Wabco Air Brake Air-Dryer Filter

RV Braking System Air Dryer Overview

"The function of the air dryer is to release moisture and air from the brake system which prevents it from going into the main system. When pressure has built up in the air system of the coach to reach its maximum set level, usually about 125 to 140 psi, the excess pressure is released from the air dryer which can be physically heard coming from the rear of the coach as the pressure is blown off when the maximum pressure in the system is attained. At this point, the front and rear pressure gauges will indicate the maximum pressure at which they are set to read (as indicated above).

The Problem

There is a filter located on top of the air dryer that traps moisture and particulate matter from going into the air system. Should this filter become full and completely clogged the moisture, etc. will pass into the main air system including the brake lines and air tanks. In areas of high humidity with a greater concentration of moisture in the air this air dryer filter becomes clogged at a faster rate than in dryer climatic conditions.

Changing the Wabco Air Brake Air-Dryer Filter

The Solution

The solution is to annually change the air dryer filter so that it will function normally. Many coach manufacturers use the Meritor Wabco brand of air dryer filter which is proven to be one of the most effective methods of protecting a coaches air brake system from moisture and contamination.

The System Saver 1200 is setting new industry standards for desiccant-type air dryers. The small, compact, lightweight design of this air dryer allows for easy installation in the limited space available in today’s aerodynamic vehicles.

Installation and Operation

Be sure to specifically request that the air dryer filter be changed annually when normal service is performed on the coach. The air dryer filter can be easily changed by the do-it-yourselfer similarly as one would change any oil filter. This filter is located on top of the air dryer usually in the side compartment adjacent to the engine compartment on most diesel pusher coaches. It will say Meritor Wabco System Saver 1200 on the side of the filter and should be easy to spot. The first item to attend to prior to changing the old filter is to dump all air from the air system. This can be done by pushing the brake pedal on and off repeatedly (called fanning) until all of the pressure is released from the air system and the air pressure gauges read zero.

There is usually a switch on the dash to dump air from the system as well. Push that switch to confirm that all of the air is out of the air system. Unlike a normal 3 inch in diameter oil filter, the air dryer filter is 5-1/2 inches in diameter, therefore you will have to use either an adjustable strap wrench or a special 5-1/2 inch filter wrench, either of which are usually available at most auto parts stores such as Napa or at Harbor Freight and Tools. To remove the old filter, simply place the wrench on the filter and turn it counter clockwise until it is free. Then remove it along with the rubber "O" ring located on the bottom of the threaded spindle that you just removed the filter from.

The new filter will contain a new rubber "O" ring which should be lubricated with vaseline then placed on the spindle where the old "O" ring was removed from. There is also a rubber gasket located on the bottom of the filter which should be coated with a thin layer of vaseline lubricant as well prior to installation. Then simply screw the new filter on the spindle spinning it clockwise till hand tight then tighten it securely with the filter or strap wrench. Finally start the engine and let the pressure build until it blows off at the bottom of the air dryer to make sure that there are no leaks.

Caution: Always consult with a professional RV mechanic, your owner's manual, and/or your authorized RV dealer BEFORE performing any maintenance or parts replacement procedures on your vehicle's braking, engine or safety systems.

To order a Meritor Wabco Series 1200 Air dryer Filter from Spartan Chassis:


Spartan Chassis
1165 Reynolds Rd.
Charlotte, MI 48813-0440

Phone: 517.543.6400

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