AIR DRYER FOR VEHICLE AIR SYSTEMS
Maintenance
NOTE: The check for water may be made at 250 service hours but it is not expected that maintenance of the desiccant will be required for at least 1000 service hours.
Put a new or rebuilt desiccant cartridge in the air dryer when the desiccant in the cartridge does not have enough water absorption ability. First, make the checks that follow.
1. Check for water in the air tanks. Open the drains on the tanks. In areas where there is more than 30° F (17° C) change in ambient temperature, there can be water in the air tanks because of condensation. A small amount of water from condensation is normal and is not an indication that the air dryer is not in operation. Steps A, B and C are probable causes of too much water in the air tanks.
A. Air from another machine without an air dryer was put in the air reservoirs and did not go through an air dryer.
B. Too much air has been used for a long time and the air compressor has not been let to load and unload in a normal way (abnormal usage of air compressor).
C. The air dryer has been installed on a machine that did not have one before. This type of system will be saturated with moisture and several weeks of operation may be needed to dry it out.
2. Check all bolts that hold the air dryer to see that they are tight. Check all air and electrical connections.
3. Check the operation of the check valve in the discharge opening of the air dryer. Install an air pressure gauge in the line between the air dryer discharge and the air tanks. With the system air pressure at governor cut-out pressure and the engine not running, check the air pressure gauge. If there is a fast drop in air pressure, it could be an indication of a check valve with a defect. This can be checked by an inspection of the purge valve exhaust. The purge valve will be open when the air pressure has gone up to governor cut-out pressure. Let two minutes go by for a complete purge cycle. If there is a constant flow of air from the purge valve exhaust with the engine shut off and if the air pressure on the test gauge went down, it is an indication there is an air leak in the check valve.
4. With the compressor loaded (compressing air), put a mixture of liquid soap and water on the exhaust of the purge valve to see if there is an air leak in the valve.
5. Pull on the stem of the relief valve while the air compressor is loaded (compressing air). There must be an exhaust of air from the valve and it must stop when the stem of the valve is released.
6. Check all lines and fittings that go to and from the air dryer for leakage.
7. Check the operation of the heater and the thermostat during cold weather operation.
