7
Section 250-0200
SM 1985 Rev 1 11-00
Braking System - Air Drier
AIR DRIER DIAGNOSIS
The following table lists some of the conditions which
could prove responsible for air drier malfunctioning.
The reasons and remedies to correct these conditions
are listed opposite each condition.
WARNING
Always shut off the engine, completely drain
the air system, and make sure the air drier is
completely purged of all air pressure before
loosening air lines or fittings to prevent
personal injury.
SERVICE TOOLS
Special tool can be fabricated as shown in Fig. 6.
Refer to Section 300-0070, SERVICE TOOLS, for part
numbers of general service tools. These tools are
available from your dealer.
Fig. 6 - Unloader Valve Adjusting Bush Installation Tool
SM - 1953
Machined
Length
1.00 in
0.75 in
0.938 in
Pins to be 0.072 in dia.
0.5 in dia.
bar
0.218 in dia.
0.343 in
0.480 in
0.475 in
dia.
Shank should be about 8 in long
and fitted with Tee handle
approx. 4 in long
AIR DRIER DIAGNOSIS CHART
CONDITION REASON REMEDY
Air continually blows Unloader valve held open by foreign Disassemble and clean unloader
out of drain port while particles on the valve seat valve assembly.
Faulty unloader valve Disconnect pilot line from the air drier
to compressor. If leak stops and air is
being expelled from the unloader valve
line, unloader valve is the problem.
Repair or replace unloader valve.
Leakage occurs while air
compressor is unloaded:
A - Continuous leakage Faulty check valve at air drier Clean or replace check valve.
B - Pulsating leakage Faulty unloader valve Clean, rebuild or replace unloader
valve.
Continuous on-off purge cycle No/Faulty check valve at air drier Install or replace check valve.
Primary tank drain cock open Close drain cock
Unloader valve malfunction If cycling occurred when air compressor
was unloaded, check unloader valve for
by-pass leakage. Check unloader valve
high-low limits.
Safety valve blowing - air drier Check system pressure when safety If pressure is below 9 bar (130 lbf/in²)
not unloading valve blows off check safety valve.
If pressure is above 9 bar (130 lbf/in²)
check unloader valve.
Large amount of water in Desiccant cartridge plugged Replace desiccant cartridge.
Desiccant saturated with water Not enough cooling of air. Check for
air line too near engine exhaust, etc.
Excessive duty cycle. Check for leakage
in air system.
compressor is pumping
primary tank
Courtesy of Machine.Market
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