Technical Bulletin Bulletin No.: PRO-08-08 Effective Date: 4-1-90 Page: 1 of 11 Subject: Air Dryer Bypass Systems for High Air Consumption Accessories Ref: Schematics (Attached) The BENDIX AD-2, 3, 4 & 9 air dryers were designed and developed to provide clean, dry air to the vehicle’s air brake system. Vehicles employing a high air consumption accessory system, such as bulk trailer unloading, generally cannot meet the minimum operational requirements for a standard air dryer installation. (Reference Bulletin PRO-08-5 or the appropriate service data manual.) While it is possible to install the Bendix air dryer on these vehicles and obtain protection for the brake system only, it is necessary to bypass the air dryer during accessory operation. Attached are several schematics which illustrate the additional components and piping that are required to bypass the air dryer during operation of the accessory system. Each schematic addresses a particular compressor or system requirement and includes a list of materials as well as a general explanation of features and some installation notes. In all bypass systems the compressor will cycle (load and unload) as required to replace air pressure used in either the brake system or accessory system, however, only air for the brake system supply will pass through the air dryer. The appropriate bypass system is chosen by determining the compressor make, model, and displacement. The attached are piping schematics only and are not construction drawings. They are presented here for discussion purposes only; for additional information, consult your Bendix representative. Before choosing one of the bypass systems presented, make certain that it fills the requirements.