Navistar ProStar+, Operation And Maintenance Manual

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Maintenance Instructions
Troubleshooting
No Restriction Reading
POSSIBLE CAUSES HOW TO CHECK
Plugged fitting or vacuum line Remove the gauge and apply a vacuum until it is locked up at the red zone. Reinsert the gauge and
hold in the reset button. Indicator will fully return unless line or fitting is plugged. A slow return is
normal due to safety filter in fitting.
Leak in vacuum line Apply vacuum to gauge until locked up at red zone. Reconnect gauge and close end of line airtight.
Hold in reset button. Indicator will drop slightly and then not move unless vacuum line has a leak.
Leak in gauge Repeat above except close gauge connection airtight.
Engine airflow too low to generate a
restriction reading Turbocharged engines must be full load to pull full engine airflow.
Air cleaner element split open Visually inspect element.
High Restriction Reading
POSSIBLE CAUSES EXPLANATION
Plugged outer element Particles in outer filter media restrict airflow. Replace outer element.
Plugged inner element (if equipped) Replace inner element.
Plugged inlet screens or ducts Check system upstream from restriction tap for debris, damage, or improper installation.
Heavy snow or rain Temporary high restriction can occur during a rain or snow storm; it disappears after drying out. If
gauge is locked up at red zone, check elements for damage. Reset gauge. Reuse element, recheck
gauge reading.
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