Bendix Commercial Vehicle Systems BA-921 SMC COMPRESSOR - Manual (Page 23)

A-10
Symptom: What it may indicate: What you should do:
(g) Restricted air inlet (not enough air
to compressor).
Check compressor air inlet line for restric-
tions, brittleness, soft or sagging hose con-
ditions, etc. Repair as necessary. Refer to
vehicle manufacturer’s guidelines for inlet
line size.
Check the engine air fi lter and service if
necessary (if possible, check the air fi lter
usage indicator).
(i) Compressor malfunction. Replace the compressor only after making
certain that none of the preceding conditions,
9.0 (a) through 9.0 (h), exist.
(h) Poorly filtered inlet air (poor air
quality to compressor).
Check for leaking, damaged or defective
compressor air inlet components (e.g.
induction line, fi ttings, gaskets, fi lter bodies,
etc.). Repair inlet components as needed.
Note: Dirt ingestion will damage compressor
and is not covered under warranty.
9.0 Air brake
charging system
seems slow to
build pressure.
(continued) (f) Restricted discharge line.  If discharge line is restricted:
 By more than 1/16" carbon build-up,
replace the discharge line (see Table A,
column 2, on page A-3 for recommended
size) and go to Test 3 on page A-14.
 By other restrictions (e.g. kinks).
Replace the discharge line. See Table A,
column 2, on page A-3 for recommended
size. Re test for air build. Return vehicle
to service or, if problem persists, go to
9.0(a).
The discharge line must maintain a
constant slope down from the compressor
to the air dryer inlet fi tting to avoid low points
where ice may form and block the fl ow.
If, instead, ice blockages occur at the air
dryer inlet, insulation may be added here,
or if the inlet fi tting is a typical 90 degree
fi tting, it may be changed to a straight or
45 degree fi tting. For more information on
how to help prevent discharge line freeze-
ups, see Bendix Bulletins TCH-008-021
and TCH-008-022 (Appendix B). Shorter
discharge line lengths or insulation may be
required in cold climates.
Kinked discharge line shown. Dash gauges.
Partly collapsed
inlet line shown.
(f)
(g)
Engine Oil Quality
Inadequate oil change intervals, the formulation of the
oil and/or the quality of oil fi lter used can all lead to poor
oil quality. These can increase the rate at which carbon
builds up in the discharge line. Bendix recommends oil
soot (solids) be maintained at less than 3%.