Air Intake Restriction Gauge
Physical instruments are listed here in alphabetical order. Some are optional and therefore not found in every vehicle. Digital instruments and gauges are described in their ICU section.
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, and has a go/no-go restriction indicator without graduations. See Fig.. As an option, a graduated indicator ( see Fig.) on the air intake duct or, for easier viewing, a dash-mounted restriction gauge may be installed.
Fig. 1, Manual-Reset Air Restriction Indicator, Go/No-Go
Fig. 2, Air Intake Restriction Indicator, Graduated
Air intake restriction vacuum is measured in inches of water (inH 2O). 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
|
Air Intake Maximum Restriction Values (inH 2O) |
|
|---|---|
|
Engine Make |
GHG14, GHG17, and GHG21 Engines |
|
Cummins |
25 |
|
Detroit |
18 |
Table 1, Air Intake Maximum Restriction Values
Note: Rain or snow can wet the filter and cause a temporary high reading.