Specifications

15
main local global operation trouble-
menu search search shooting
COMPRESSOR TROUBLESHOOTING CHART (Continued)
SYMPTOMS
F. Sticking unloader
pistons.
CAUSE
REMEDY
G. Faulty compressor.
4. Compressor fails to
unload.
5. Compressor leaks oil.
A. Faulty governor or
governor installation.
B. Faulty or worn unloader
pistons or bores.
A. Damaged mounting
gasket.
B. Cracked crankcase or
end cover.
The pressure drop for Post-1975 vehicles should
not exceed:
1. 2 psi in each reservoir for a single vehicle.
2. 6 psi in each reservoir for a tractor and trailer.
3. 8 psi in each reservoir for a tractor and 2
trailers.
F. Check the operation of the unloading pistons in
the inlet cavity of the compressor. Both pistons
should have the plunger flanges resting on the
inlet cavity floor when the compressor is loaded
(pumping air). If the pistons and plunger are not
fully retracted, check for proper operation of the
compressor air governor. If the governor is
operating properly, replace the unloader pistons
and plungers and inspect their bores in the
cylinder block. Clean lubricate as necessary.
Inspect for bent, linked or blocked tubing leading
to or from the governor.
G. Replace or repair the compressor after
determining none of the preceding installation
defects exist.
A. Test the governor for proper operation and
inspect air lines to and from the governor for
kinks or restrictions. Replace or repair the
governor or its connecting air lines.
B. Inspect for worn, dirty or corroded unloader
pistons and their bores. Replace as necessary.
A. Check the compressor mounting bolt torque. If
the mounting bolt torque is low, replace the
compressor mounting gasket before retorquing
the mounting bolts.
B. Visually inspect the compressor exterior for
cracked or broken components. Cracked or
broken crankcases or mounting flanges can be
caused by loose mounting bolts. The end cover
can be cracked by overtorquing fitting or plugs
installed in the end cover. Replace or repair the
compressor as necessary.
C. Check the cap screw torques and tighten as
necessary.
D. Check the torque of external oil line fittings and
tighten as necessary.
E. Replace the compressor if porosity is found.
C. Loose end cover cap
cover.
D. Loose oil supply or
return line fittings.
E. Porous compressor
casting.
3. (Continued)