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Symptom:
12.0 Air dryer
safety valve
releases air.
Air dryer
safety valve
Technician removes
governor.
13.0 Reservoir
safety valve
releases air.
14.0 Air dryer
doesn't purge.
(Never hear
exhaust from air
dryer.)
15.0 Compressor
constantly cycles
(compressor
remains unloaded
for a very short
time.)
(b) is not applicable for the
compressor featured in this SD
sheet —- information is shown
for reference only.
A-12
What it may indicate:
(a) Restriction between air dryer and
reservoir.
(b) Air dryer safety valve
malfunction.
(c) Air dryer maintenance not
performed.
(d) Air dryer malfunction.
(e) Improper governor control line
installation to the reservoir.
(f) Governor malfunction.
(a) Reservoir safety valve
malfunction.
(b) Governor malfunction.
(c) Compressor unloader mechanism
malfunction.
(a) Air dryer malfunction.
(b) Governor malfunction.
(c) Air brake system leakage.
(d) Improper governor control line
installation to the reservoir.
(a) A i r b r a k e c h a r g i n g s y s t e m
maintenance not performed.
(b) Compressor unloader mechanism
malfunction.
(c) Air dryer purge valve or delivery
check valve malfunction.
(d) Air brake system leakage.
What you should do:
Inspect delivery lines to reservoir for
restrictions and repair as needed.
Verify relief pressure is at vehicle or
component manufacturer specifi cations.
Replace if defective.
See Maintenance Schedule and Usage
Guidelines (Table A, column 3, on page
A-3).
Verify operation of air dryer. Follow vehicle
O.E. maintenance recommendations and
component Service Data information.
Go to Test 5 on page A-15.
Go to Test 4 on page A-15.
Verify relief pressure is at vehicle or
component manufacturer's specifi cations
(typically 150 psi). Replace if defective.
Go to Test 4 on page A-15.
Go to Test 6 on page A-15.
Verify operation of air dryer. Follow vehicle
O.E. maintenance recommendations.
Go to Test 4 on page A-15.
Go to Test 2 on page A-14.
Go to Test 5 on page A-15.
Available reservoir capacity may be
reduced by build-up of water etc. Drain and
perform routine maintenance per Table A,
columns 3 & 4, on page A-3.
Go to Test 6 on page A-15.
Verify operation of air dryer. Follow vehicle
O.E. maintenance recommendations and
component Service Data information.
Go to Test 2 on page A-14.
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