Bendix Commercial Vehicle Systems BENDIX 720CC COMPRESSOR - Manual (Page 25)

A-11
Symptom: What it may indicate: What you should do:
10.0 Air charging
system doesn’t
build air.
(a) Governor malfunction*.
(b) Restricted discharge line.
(c) Air dryer heater malfunction:
exhaust port frozen open.
(d) Compressor malfunction.
 Go to Test 4 on page A-15.
 See 9.0(f).
 Replace air dryer heater.
 Replace the compressor only after making
certain the preceding conditions do not
exist.
11.0 Compressor
safety valve
releases air
(Compressor
builds too much
air).
(a) Restricted discharge line.
 If the 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.
 The discharge line must maintain a
constant slope down from the compressor
to the air dryer inlet fitting to avoid low points
where ice may form and block the flow.
If, instead, ice blockages occur at the air
dryer inlet, insulation may be added here,
or if the inlet fitting is a typical 90 degree
fitting, it may be changed to a straight or
45 degree fitting. 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.
 Inspect air lines and verify check valves are
operating properly.
 Ensure discharge line is installed into the
inlet of the air dryer and delivery is routed
to the service reservoir.
 Verify relief pressure is 250 psi. Replace if
defective.
 Go to Test 6 on page A-15.
 Go to Test 4 on page A-15.
Damaged
discharge
line shown.
* Note: For the Bendix ® DuraFlo 596 ™ air compressor, not only
the governor, but also the SV-1 ™ synchro valve used would
need to be tested. See Bulletin TCH-001-048.

(b) Downstream air brake system check
valves or lines may be blocked or
damaged.
(c) Air dryer lines incorrectly installed.
(d) Compressor safety valve
malfunction.
(e) Compressor unloader mechanism
malfunction.
(f) Governor malfunction.