Air Intake Restriction Gauge
The air intake restriction gauge indicates the vacuum on the engine side of the air cleaner. On standard installations, it is mounted on the air intake duct in the engine compartment. See Fig.. As an option for easier viewing, the air intake restriction indicator can be mounted on the dash, usually on the right-hand control panel.
Fig. 1, Air Intake Restriction Indicator
Note: Rain or snow can wet the filter and cause a temporary high reading.
Air intake restriction vacuum is measured in inches of water (inH2O). For vehicles equipped with a graduated indicator or a restriction gauge on the dash, check the gauge with the engine off. If the yellow signal stays locked in the red zone once the engine is shut down, or is at or above the values shown in Table., the air cleaner element needs to be replaced.
Table 1, Air Intake Maximum Restriction Values
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Air Intake Maximum Restriction Values (in H2O) |
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Engine Make |
GHG14, GHG17, and GHG21 Engines |
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Detroit |
18 |
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Cummins |
25 |
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Table 1, Air Intake Maximum Restriction Values
Vehicles may be equipped with a go/no-go restriction indicator without graduations (see Fig.) instead of a graduated indicator.
