BENDIX DRM DRYER RESERVOIR MODULE User manual

1
Air
Connection Function/Connection No.
Port ID
DESCRIPTION
The function of the dryer reservoir module (DRM™) is to
provideheavyvehicleswithanintegratedvehicleairdryer,
secondaryreservoir,purgereservoir,governorandanumber
ofthechargingvalvecomponentsinamodule. TheDRM™
dryer module model covered in this Service Data Sheet is
the first to be released, see updates to this Service Data
Sheetforother models.
TheDRM™dryermoduleincludesanintegrated solution air
dryer (AD-IS®), a reservoir (including a separate purge
reservoir section) a governor and four pressure protection
valves. Thesehavebeendesignedasanintegratedairsupply
system.
ThefunctionoftheAD-IS®airdryeristo collect and remove
air system contaminants in solid, liquid and vapor form
before they enter the brake system. It provides clean, dry
airtothecomponentsofthebrakesystemwhichincreases
thelifeof thesystemandreduces maintenancecosts. Daily
manual draining of the reservoirs is eliminated.
The function of the pressure protection valves is to both
controlthe order in which the components receive airfrom
theAD-IS®airdryer,andalsotoprotecteach reservoir from
a pressure loss in the other reservoir or a pressure loss in
an air accessory.
FIGURE 1 - DRYER RESERVOIR MODULE
The air dryer consists of a “spin on” desiccant cartridge
secured to a base assembly.
The base assembly contains a delivery check valve
assembly, safety valve, heater and thermostat assembly,
pressure protection valves, threaded air connections and
thepurgevalveassembly.
Bendix®Dryer Reservoir Module with AD-IS®Air Dryer
SD-98-9808
1
IN
21
PRI
22
AUX1
23
AUX2
UNL UnloaderControlAir(D-2A™Governor) 2
RES CommonReservoirPressure(D-2A™Governor) 2
EXH GovernorExhaust 1
TABLE 1 - DRM™DRYER MODULE AIR CONNECTIONS
Inlet Port (air in). 1
Delivery Port out (to Primary reservoir) 1
Auxiliary Delivery Port (air out). 4
Auxiliary Delivery Port (air out). 1
DESICCANT
CARTRIDGE
SECONDARY
RESERVOIR AD-IS®
Air Dryer
INTEGRATED
PURGE RESERVOIR
GOVERNOR
PRESSURE PROTECTION
VALVES (4)
AUXILIARY
DELIVERY PORTS
(5)
HEATER/
THERMOSTAT
SAFETY VALVE
AD-IS®AIRDRYER PART NUMBERSTAMPED HERE
MOUNTING
BOLTS (3)

2
FIGURE 2 - AD-IS
®
AIR DRYER CHARGE CYCLE. DIAGRAM SHOWS PRESSURE PROTECTION VALVES A AND B OPEN, C & D CLOSED.
COMPRESSOR
GOVERNOR
PURGE
CONTROL
CHANNEL
DESICCANT
BED
DELIVERY
CHECK
VALVE
(OPEN) PURGE RESERVOIR
PRIMARY
PORT
(PRI)
PURGE
VALVE
(CLOSED)
TURBO
CUTOFF
VALVE
(OPEN)
ENGINE
TURBO
UNLOADER
PORT
INLET
PORT
(IN)
OIL
SEPARATOR
PURGE
ORIFICE
PRIMARY
RESERVOIR
SECONDARY
RESERVOIR
PRESSURE PROTECTION
VALVES
AUXILIARY PORTS
(TO ACCESSORIES)
SEE
NOTE 1
Note 1:
TheAD-IS®air dryer purgepistonhasa
purgecontrolchanneldrain.Thisallows
any condensation in this area to flow
pastadiaphragm inthetopofthepurge
pistonandoutthroughachannelinthe
middle of the central bolt of the purge
assembly to be drained. During the
purge cycle this drain is closed.
SAFETY
VALVE
PURGE
RESERVOIR
DRAIN VALVE
Theremovablepurgevalveassemblyincorporatesthepurge
valve mechanism and a turbocharger cutoff feature that is
designed to prevent loss of engine “turbo” boost pressure
during the purge cycle of theAD-IS®air dryer. For ease of
serviceability, all replaceable assemblies can be replaced
without removal of the air dryer from its mounting on the
vehicle. RefertoPreventiveMaintenancesection.
DRM™DRYER MODULE OPERATION:
GENERAL (Refer to Figure 2)
TheDRM™dryermoduleisdesignedtoreceivecompressed
air from the vehicle air compressor, clean and dry the air
using theAD-IS®airdryer,deliverairtothevehicle’sprimary
reservoir,secondaryreservoir and accessories,andcontrol
thecompressor/dryer charge cycle.
AIR DRYER OPERATION: GENERAL
The AD-IS®air dryer alternates between two operational
modes or “cycles”duringoperation: the ChargeCycle and
thePurgeCycle. The following descriptions are separated
into these “cycles” of operation.
CHARGE CYCLE (Refer to Figure 2)
When the compressor is loaded (compressing air)
compressed air, along with oil, oil vapor, water and water
A
D
CB

3
FIGURE 3 - AD-IS®AIR DRYER PURGE CYCLE.
COMPRESSOR
GOVERNOR
PURGE
CONTROL
CHANNEL
DESICCANT
BED
DELIVERY
CHECK
VALVE
(CLOSED) PURGE
RESERVOIR
PURGE
VALVE
(OPEN)
TURBO
CUTOFF
VALVE
(CLOSED)
ENGINE
TURBO
OIL
SEPARATOR
PURGE
ORIFICE
PRIMARY
RESERVOIR
SECONDARY
RESERVOIR
GOVERNOR SIGNALS AIR
COMPRESSOR TO SUSPEND
COMPRESSED AIR SUPPLY
TOAD-IS®AIRDRYER
EXHAUST
PRIMARY
PORT
(PRI)
UNLOADER
PORT
INLET
PORT
(IN)
SAFETY
VALVE AUXILIARY PORTS
(TO ACCESSORIES) PURGE
RESERVOIR
DRAIN VALVE
vapor flows through the compressor discharge line to the
inlet (1 IN) port of the air dryer body.
As air travels through theAD-IS®air dryer, its temperature
falls, causing some of the contaminants to condense and
drop to the bottom of the air dryer purge valve assembly,
ready to be expelled at the next purge cycle. The air then
flowsintothedesiccantcartridge,where it flows throughan
oilseparatorwhichremovesliquidoilandsolidcontaminants.
Air then flows into the desiccant drying bed and becomes
progressivelydrieraswatervapor adheres tothedesiccant
material in a process known as “ADSORPTION.”
Dry air exits the desiccant cartridge through the center of
thebaseassembly. Theairthen flows to thedeliverycheck
valve and also through an orifice into the purge reservoir.
Thedeliverycheckvalveopens,supplyingairtothepressure
protection valves (A) and (B), the safety valve, and also to
thereservoirportoftheattachedgovernor. Thepurgereservoir
fills,storing air that will be usedto reactivate the desiccant
duringthe purge cycle.
When the air pressure reaches approximately 103 p.s.i.,
the first pressure protection valve (A) will open and air will
besuppliedtotheprimary reservoir. When theairpressure
in the primary reservoir reaches approximately 109 p.s.i.,
PRESSURE PROTECTION
VALVES
A
D
CB

4
thesecondpressureprotectionvalve(B)opensandairwill
besuppliedto the secondaryreservoirandto theaccessory
pressure protection valves (C & D). (Note: there is no
external air hose feeding the secondary reservoir, instead
airissuppliedby a connectorpassingthroughthebulkhead
ofthepurge reservoirsectionofthereservoir.) Whentheair
pressureinthesecondaryreservoir reaches approximately
55 p.s.i. and 85 p.s.i. respectively, the two remaining
pressureprotectionvalves(C&D)willopenandsupply air
to the vehicle accessories.
The air dryer will remain in the charge cycle until the air
brakesystempressurebuilds to thegovernorcutoutsetting
of approximately 130 p.s.i.
PURGE CYCLE (Refer to Figure 3.)
Whenairbrakesystempressure reaches the cutoutsetting
ofthegovernor,thegovernorunloads the compressor and
the purge cycle of the air dryer begins.
The governor unloads the compressor by allowing air
pressureto fill the line leading to the compressor unloader
mechanism - causing the delivery of compressed air to
theAD-IS®air dryer to be suspended.
Similarly, the governor also supplies air pressure to the
AD-IS®airdryerpurge controlchannel. TheAD-IS®airdryer
purgepiston moves down in response to this air pressure,
causingthepurgevalvetoopentotheatmosphere and the
turbo cutoff valve to close off the supply of air from the
compressor (this will be further discussed in the Turbo
Cutoff Feature section). Water and contaminants which
have collected in the purge valve base are expelled
immediately when the purge valve opens. Also, air which
wasflowingthroughthedesiccantcartridgechangesdirection
and begins to flow toward the open purge valve. Oil and
solidcontaminantscollectedbytheoilseparatorareremoved
byairflowing fromthepurgereservoirthroughthedesiccant
dryingbedtotheopenpurgevalve.
The initial purge and desiccant cartridge decompression
lasts only a few seconds and is evidenced by an audible
burst of air at theAD-IS®air dryer exhaust.
The actual reactivation of the desiccant drying bed begins
asdry air from the purge reservoir flows throughthe purge
orifice into the desiccant bed. Pressurized air from the
purge reservoir expands after passing through the purge
orifice; its pressure is lowered and its volume increased.
The flow of dry air through the drying bed reactivates the
desiccant material by removing the water vapor adhering
toit. Approximately 30 seconds are required forthe entire
contentsofthepurge reservoirofa standardAD-IS®airdryer
to flow through the desiccant drying bed.
Thedeliverycheckvalveassembly prevents airpressurein
the brake system from returning to the air dryer during the
purgecycle.Afterthepurgecycleiscomplete,theairdryer
is ready for the next charge cycle to begin.
TURBO CUTOFF FEATURE (Refer to Figure 3.)
The primary function of the turbo cutoff valve is to prevent
loss of engine turbocharger air pressure through the
AD-IS®air dryer in systems where the compressor intake
isconnected to the engine turbocharger.
Atthe onset of the purge cycle, the downward travel of the
purge piston is stopped when the turbo cutoff valve
(taperedportion of purge piston) contacts its mating metal
seatinthepurgevalvehousing. Withtheturbo cutoff valve
seated (closed position), air in the compressor discharge
lineandAD-IS®airdryerinletport cannot entertheairdryer.
In this manner the turbo cutoff effectively maintains turbo
chargerboost pressure to the engine.
PREVENTIVE MAINTENANCE
Important: Reviewthe warranty policy before performing
any intrusive maintenance procedures. An extended
warranty may be voided if intrusive maintenance is
performed during this period.
Because no two vehicles operate under identical
conditions, maintenance and maintenance intervals will
vary. Experience is a valuable guide in determining the
bestmaintenanceintervalforanyoneparticularoperation.
Every 900 operating hours, or 25,000 miles or three (3)
months:
1. Check for moisture in the air brake system by opening
reservoir drain valves and checking for presence of
water. If moisture is present, the desiccant cartridge
may require replacement; however, the following
conditions can also cause water accumulation and
should be considered before replacing the desiccant:
A. An outside air source has been used to charge the
system. This air does not pass through the drying
bed.
B. Air usage is exceptionally high and not normal.
This may be due to high air system leakage.
C. In areas where more than a 30 degree range of
temperature occurs in one day, small amounts of
water can temporarily accumulate in the air brake
system due to condensation. Under these
conditions, the presence of small amounts of
moisture is normal.
Note: A small amount of oil in the system is normal and
should not be considered as a reason to replace the
desiccantcartridge. Someoilatthedryerexhaustisnormal.
2. Visually check for physical damage such as chaffed or
broken air and electrical lines and broken or missing
parts.
3. Check mounting bolts for tightness. See Figure 1.
Re-torqueto360-420inch pounds.

5
4. Perform the Operation & Leakage Tests listed in this
publication.
WARNING!
This air dryer is intended to remove moisture and other
contaminants normally found in the air brake system.
Do not inject alcohol, anti-freeze, or other de-icing
substances into or upstream of the air dryer. Alcohol
is removed by the dryer, but reduces the effectiveness
of the device to dry air. Use of other substances can
damage the air dryer and may void the warranty.
OPERATION & LEAKAGE TESTS (ALSO SEE
VIDEO BW2327)
1. Check all lines and fittings leading to and from the air
dryerforleakageandintegrity. Repairany leaks found.
2. Build up system pressure to governor cutout and note
thattheAD-IS®airdryerpurgeswithanaudibleescape
ofair. Watchthesystempressure and notethepressure
fall-offfora tenminuteperiod. Ifpressuredropexceeds,
for a single vehicle - 1 psi/minute from either service
reservoir; or for tractor trailer - 3 psi/minute from either
service reservoir, inspect the vehicle air systems for
sources of leakage and repair them. Refer to section
entitled Troubleshooting, Symptoms 1 and 4.
3. Check for excessive leakage around the purge valve
with the compressor in the loaded mode (compressing
air). Apply a soap solution to the purge valve exhaust
port and observe that leakage does not exceed a 1"
bubblein1second. Iftheleakageexceedsthemaximum
specified, refer to section entitled Troubleshooting,
Symptom 4.
4. Build up system pressure to governor cutout and note
thattheAD-IS®airdryerpurgeswithanaudibleburstof
air,followedimmediatelybyapproximately30seconds
of air flowing out of the purge valve. “Fan” the service
brakes to reduce system air pressure to governor cut-
in. Notethatthesystemonceagainbuildstofullpressure
and is followed by anAD-IS®air dryer purge. If system
does not follow this pattern, refer to section entitled
Troubleshooting, Symptoms 5 and 6.
5. Check the operation of the end cover heater and
thermostat assembly during cold weather operation as
follows:
A. Electric Power to the Dryer
With the ignition or engine kill switch in the RUN
position, check for voltage to the heater and
thermostat assembly using a voltmeter or testlight.
Unplug the electrical connector at the air dryer and
place the test leads on each of the connections of
the female connector on the vehicle power lead. If
there is no voltage, look for a blown fuse, broken
wires, or corrosion in the vehicle wiring harness.
Check to see if a good ground path exists.
B. ThermostatandHeater Operation
Note: These tests are not possible except in cold
weather operation.
Turnofftheignitionswitchandcool the thermostat and
heater assembly to below 40 degrees Fahrenheit.
Usinganohmmeter,checkthe resistance between the
electrical pins in the air dryer connector half. The
resistance should be 1.5 to 3.0 ohms for the 12 volt
heater assembly and 6.0 to 9.0 ohms for the 24 volt
heater assembly.
Warm the thermostat and heater assembly to
approximately90degreesFahrenheitandagaincheck
the resistance. The resistance should exceed 1000
ohms. If the resistance values obtained are within the
stated limits, the thermostat and heater assembly is
operating properly. If the resistance values obtained
are outside the stated limits, replace the heater and
thermostat assembly.
6. Pressureprotectionvalves. Observethepressuregauges
ofthevehicleas system pressurebuildsfromzero. The
primarygaugeshould riseuntilitreachesapproximately
109 psi (±5 psi), then level off (or a momentary slight
fall) as the second pressure protection valve opens
supplyingthesecondaryreservoir. When thesecondary
pressure gauge passes through approximately 55 (±5
psi)andthen85psi(±5psi)thereshouldbeanassociated
levelingoff(ormomentaryslightfall)ofpressureasthe
thirdandfourth pressureprotectionvalvesopen. Finally
both the primary and secondary gauges should reach
theirfull pressure of approximately 130 psi (±5 psi).
If the AD-IS®air dryer does not perform within the
pressure ranges as described above recheck using
gauges known to be accurate. If the readings remain
outside of the ranges outlined above, replace the
AD-IS®air dryer. NOTE: There are no kits available for
FIGURE 4 - AD-IS®AIR DRYER HEATER AND
THERMOSTAT CONNECTOR
HEATER & THERMOSTAT
CONNECTOR

6
the servicing of the pressure protection valves.
WARNING: Do not attempt to adjust or service the
pressure protection valves - incorrect pressure
protection valve settings can result in automatic
applicationof thevehiclespring brakeswithout prior
warning.
REBUILDING THE AD-IS®AIR DRYER
GENERAL SAFETY GUIDELINES
WARNING! PLEASE READAND FOLLOW THESE
INSTRUCTIONS TO AVOID PERSONAL INJURY
OR DEATH:
When working on or around a vehicle, the following
general precautions should be observed at all times.
1. Park the vehicle on a level surface, apply the
parking brakes, and always block the wheels.
Always wear safety glasses.
2. Stop the engine and remove ignition key when
working under or around the vehicle. When
working in the engine compartment, the engine
should be shut off and the ignition key should be
removed. Where circumstances require that the
engine be in operation, EXTREME CAUTION should
be used to prevent personal injury resulting from
contact with moving, rotating, leaking, heated or
electrically charged components.
3. Do not attempt to install, remove, disassemble or
assemble a component until you have read and
thoroughly understand the recommended
procedures. Use only the proper tools and observe
all precautions pertaining to use of those tools.
4. If the work is being performed on the vehicle’s air
brake system, or any auxiliary pressurized air
systems,makecertainto drain the airpressurefrom
all reservoirs before beginning ANY work on the
vehicle. If the vehicle is equipped with an AD-IS®
air dryer system or a dryer reservoir module, be
sure to drain the purge reservoir.
5. Following the vehicle manufacturer’s
recommended procedures, deactivate the electrical
systeminamanner that safelyremovesall electrical
power from the vehicle.
6. Never exceed manufacturer’s recommended
pressures.
7. Never connect or disconnect a hose or line
containing pressure; it may whip. Never remove a
componentorplug unless youarecertain all system
pressure has been depleted.
8. Use only genuine Bendix®replacement parts,
components and kits. Replacement hardware,
tubing,hose,fittings, etc. mustbeof equivalent size,
type and strength as original equipment and be
designed specifically for such applications and
systems.
9. Components with stripped threads or damaged
parts should be replaced rather than repaired. Do
not attempt repairs requiring machining or welding
unless specifically stated and approved by the
vehicle and component manufacturer.
10.Prior to returning the vehicle to service, make
certain all components and systems are restored
to their proper operating condition.
11.For vehicles with Antilock Traction Control (ATC),
the ATC function must be disabled (ATC indicator
lamp should be ON) prior to performing any vehicle
maintenance where one or more wheels on a drive
axle are lifted off the ground and moving.
WARNING:
DO NOT ATTEMPT TO ADJUST OR
SERVICE THE PRESSURE PROTECTION
VALVES. INCORRECT PRESSURE
PROTECTION VALVE SETTINGS CAN
RESULT IN AUTOMATIC APPLICATION OF
VEHICLE SPRING BRAKES WITHOUT
PRIOR WARNING.
FIGURE 5 - PRESSURE PROTECTION VALVE LOCATIONS
PRESSURE
PROTECTION
VALVE
LOCATIONS
AD-IS
®
AIR DRYER
GOVERNORS
ARE NON-
ADJUSTABLEAND
FEATUREA
BREATHERVALVE
IN THIS PORT

7
• ServiceNewPurgeValveHousingAssembly: Contains
a service new assembly and related components to
change the purge valve sub-assembly.
• PressureProtectionValveBootReplacement.
• AD-IS®AirDryerReplacement: Replacesthecomplete
air dryer assembly. Includes air dryer assembly and
governor.
• AD-IS®AirDryer Splash Shield Replacement Kit.
• PurgeReservoirDrainValve: Replacesthedrainvalve
on the purge reservoir.
SEE CATALOG PAGE 98-A-1 FOR FULL LIST OF
MAINTENANCE KITSAVAILABLE.
NOTE: There is no kit available for the servicing of the
pressureprotection valves (See Figure 5). Do not attempt
to adjust or service the pressure protection valves - these
arenot service items.
TESTING THE AD-IS®AIR DRYER
Beforeplacingthevehicleinservice, perform the following
tests.
1. Closeallreservoirdrainvalves.
2. Build up system pressure to governor cutout and note
thattheAD-IS®airdryerpurgeswithanaudibleburstof
air,followedimmediatelybyapproximately30seconds
ofairflowingout of thepurgevalve.
GENERAL
When rebuilding or replacing components of the air dryer
use only genuine Bendix parts. For ease in servicing, the
AD-IS®air dryer has been designed so that any of the
followingmaintenancekitscanbe installedwithoutremoving
theair dryer from the vehicle.
If,aftercompletingtheroutineoperation and leakage tests,
ithasbeendeterminedthat one ormorecomponentsofthe
airdryerrequiresreplacementormaintenance,refertothe
following list to find the appropriate kit(s).
MAINTENANCE KITS AVAILABLE:
• Service New Desiccant Cartridge Kit: This kit contains
the parts necessary to change the desiccant cartridge
only.
• DeliveryCheckValveMaintenance Kit: Thiskitcontains
thepartsnecessarytoreplace the deliverycheckvalve.
• Governor/Delivery Check Valve Kit: This kit contains
the parts necessary to replace both the governor and
delivery check valve.
• 12voltor24voltHeaterand Thermostat Kits: Contains
a replacement heater and thermostat assembly and
related components required for replacement.
• PurgeValveHousingMaintenance Kit: Thiskitcontains
the parts necessary to rebuild the purge valve sub-
assembly.
FIGURE 6 - SPLASH SHIELD BRACKET AND COVER - (EXPLODED VIEW)
SPLASH
SHIELD
BRACKET
SPLASH
SHIELD
COVER
LOCK TABS

8
3. “Fan”theservicebrakestoreducesystemairpressure
to governor cut-in. Note that the system once again
builds to full pressure and is followed by a purge at the
AD-IS®airdryerexhaust.
4. Itisrecommendedthatthe total air system betestedfor
leakagetoassurethattheAD-IS®airdryerwillnotcycle
excessively.
SeeBendixpublicationBW-5057“AirBrake Handbook.”
BRAKING SYSTEM PROTECTION
The DRM™dryer module allows the system to maintain
onebrake circuit up to about 100 psieven after a pressure
loss in the other brake circuit. This allows a vehicle to be
moved(in anemergency),butwithreducedbrakingcapacity.
Compare this to a conventional system where a loss of
pressureinoneservicetankleaves thevehiclewithalimited
numberofreducedbraking capacityapplicationsbeforethe
parking brakes automatically apply and stay on.
ROADSIDE INSPECTION
In the event of a roadside inspection the system behavior
willbeasfollows: Whenthesystemischarged to governor
cut out, and then one reservoir drain valve is opened,
initiallybothreservoir gauges will fall, however,theAD-IS®
airdryer'sprimaryandsecondarypressureprotectionvalves
willcloseatpressuresabove70psi,protectingtheremaining
brake circuit from further loss of pressure.
TEMPORARY AIR DRYER BYPASS
Totemporarilybypassthe airdryer,thefollowingprocedure
needs to be followed.
FollowtheMaintenancePrecautionsoutlinedelsewherein
this document.
Make sure that all residual pressure has been released,
then remove the air supply line from the compressor to
the inlet port (1 IN). Remove the safety valve from the
AD-IS®airdryerbody(seeFigure1for location) and install
a T-fitting into the port. Using any adapters necessary,
re-install the safety valve in one of the branches of the
T-fitting. Using anyadaptersnecessary,installtheairsupply
line into the remaining T-fitting port. After testing the
T-fitting for any air leakage, using a soap solution after
charging system pressure (a 1” bubble in 10 seconds is
acceptable), the vehicle may be returned to temporary
service.
Note: This is a temporary bypass of the air dryer, and
full repair of the unit must be carried out at the earliest
opportunity. Withtheairdryerremoved from the system,
contaminants will be entering the air system: reservoirs
will need to be manually drained daily until the repairs are
completed. At end of each working day, park vehicle and
slowlydrainpressurethrough the drainvalves–leaveopen
to the atmosphere, for several hours if possible. When
repairs are carried out, be sure to check that all reservoirs
(includingthepurgereservoirincorporatedintothesecondary
reservoir)areemptiedofallcontaminants.
If after bypassing the dryer reservoir module the system
pressurestilldoesnotbuild,usethefollowingprocedureto
remove,cleanandreinstallthedeliverycheckvalve.
DELIVERYCHECKVALVECLEANING PROCEDURE
(Note: This is only required if system pressure does not
build after temporary bypass is completed.)
See Figure 7 throughout this procedure. Depressurize
the air brake system following the general safety
precautions outlined elsewhere in this document.
This procedure does not require removal of theAD-IS®air
dryer from the vehicle.
1. Remove line from governor and mark for easy
reinstallation.
2. Remove bolts attaching the governor to the AD-IS®air
dryerandretainfor reassembly.
3. Removegovernorandtheadapter’so-ring.
4. The spring/delivery check valve can now be removed.
(Note: The spring/delivery check valve may be a
previous design. See Figure 7.)
5. Removeo-ringfromcheck valvebody.
CLEANING & INSPECTION
1. Use a suitable solvent to clean all metal parts, and use
a cotton swab to clean the bore (Note: Do not use
abrasives or tools to clean the bore: any scratches
causedmaynecessitatereplacing theAD-IS®airdryer.)
Superficial external corrosion and/or pitting is
acceptable.
2. Clean the o-rings with a clean dry cloth. Do not use
solvents.
3. Inspect for physical damage to the bore and the check
valve seat. If the bore is damaged (by scratches etc.
that would prevent delivery check valve from seating),
replacetheAD-IS®air dryer.
4. Inspectthedeliverycheck valve,o-rings,etc.for wearor
damage. Replace if necessary using the check valve
replacement kit available at authorized Bendix parts
outlets.
5. Inspect all air line fittings for corrosion and replace as
necessary.

9
FIGURE 7 - AD-IS®AIR DRYER DELIVERY CHECK VALVE
GOVERNORGASKET
(SPECIALGASKET,
SEE NOTE 6 ON
PREVIOUSPAGE) GOVERNOR
(NON-ADJUSTABLE,
130 PSI CUT-OUT)
BOLTS
ADAPTER
LARGE
O-RING
SPRING
CHECKVALVE
BODY
SMALL
O-RING
ORIGINALSTYLE
CHECKVALVEAND
SPRING
Early models include a different style check
valve and spring
ASSEMBLY
1. Lubricate the smaller o-ring and check valve body with
barium or silicon grease.
2. Installthiso-ringonthecheckvalvebodyby sliding the
o-ring over the set of 4 tapered guide lands. The
o-ringgrooveholdstheo-ringinitscorrect location.
3. At the other end of the check valve body, the spring is
installed over the set of 4 straight guide lands. When
the spring has been pushed to the correct location, the
checkvalvebodyisdesignedtoholdtheendofthespring
in position - be sure that the spring is not loose before
continuing with this installation.
4. Installtheassembledcheckvalvebody/o-ring/springin
the delivery port so that the o-ring rests on its seat and
the free end of the spring is visible.
5. Greasetheadapterandthe remaining larger o-ring and
install it onto the fitting.
6. Position gasket, insert bolts through the governor and
tighten (to 125 in-lbs). (Note: Do not replace with a
standard compressor/governor gasket.)
7. Reattachlinetothe governor.
8. Before placing vehicle back into service, check to see
that the system pressure now builds to full operational
pressure.

10
DRM™/AD-IS®AIR DRYER TROUBLESHOOTING CHART
SYMPTOMS
1. Dryer is constantly
“cycling”orpurging. A. Test for excessive system leakage. Allowableleakageobservedatdashgauge:
Single vehicle - 1 psi/minute.
Tractor trailer - 3 psi/minute.
Using soap solution, test vehicle for leakage at
fittings,drainvalvesandsystemvalves.Repair
or replace as necessary.
B. Build system pressure to governor cut-out. Wait
1 minute for completion of purge cycle. Using
soapsolutionat exhaust of purge valve, leakage
should not exceed a 1" bubble in less than 5
seconds.
If a rapid loss of pressure is found, the following
procedurewilldetermine if the delivery check
valveismalfunctioning:
Buildsystempressuretogovernorcut-outandallow
a full minute for the normal dryer purge cycle to
empty the purge reservoir. Switch off the engine
and “fan” the brakes so that the system pressure
reachesgovernorcut-in. Thepurgevalvewillreturn
to its closed position. The purge reservoir has a
drain valve which is opened by moving the center
leverawayfromits closedposition.Openthedrain
valve and wait 10 seconds to allow any residual
purgepressuretobereleased. Releasethe lever,
closing the drain valve. Carefully remove the air
dryercartridgeusingastrapwrenchandthentest
for air leaking through the center of the threaded
boss by applying a soap solution to the boss.
Replace the delivery check valve if there is
excessive leakage (exceeding a 1" bubble in 5
seconds).
Regreasethesealon theairdryercartridgebefore
reinstalling. Be sure the drain valve on the purge
reservoir is not leaking before restoring vehicle to
service.
C. Check governor at both “cut-in” and “cut-out”
positionfor (i) proper pressures and (ii)
excessive leakage at fittings and exhaust.
D. Remove air strainer or fitting from compressor
inlet cavity. With compressor unloaded, check
forunloaderpiston leakage. Slight leakage
permissible.
A. Excessive system
leakage.
CAUSE REMEDY
B. Defectivedeliverycheck
valve.
C. Defectivegovernor.
D. Compressorunloader
mechanismleaking
excessively.

11
DRM™/AD-IS®AIR DRYER TROUBLESHOOTING CHART (Continued)
SYMPTOMS CAUSE REMEDY
D. Replace desiccant cartridge assembly.
D. Desiccant requires
replacement.
E. Air by-passes desiccant
cartridgeassembly.
F. Air dryer not purging.
G. Purge (air exhaust)time
insufficientdueto
excessive system
leakage.
A. Maximum air dryer inlet
temperatureis
exceededdue to
improperdischargeline
length.
B. Air system charged from
outsideair source
(outsideair not passing
throughairdryer).
C. Excessive air usage -
Airdryer not compatible
with vehicle air system
requirement(Improper
airdryer/vehicle
application).
A. Check for excessive carbon build up in
compressordischarge line. Replace if
required. Make certain that discharge line
length is at least 6 ft. Increase discharge line
lengthand/or diameter to reduce air dryer inlet
temperature.
B. If system must have outside air fill provision,
outside air should pass through air dryer.
2. Water in vehicle
reservoirs.
C. Note: TheAD-IS®air dryer is not intended for
use on applications with excessive air usage.
Thefollowingapplicationsrequiremoredryair
than theAD-IS®air dryer is designed to supply.
Do not use on:
1) City buses.
2) Vehicle combinations with more than 8 braked
axles.
3) City refuse vehicles except those with work
brakes.
4)Concrete mixers.
5) Dump trucks with more than 3 axles.
6)Off-highway/constructionvehicleswithmore
than 7 braked axles.
7) Vehicles with compressor on times in excess
of20%.
Ifthe vehicle is equipped with high air usage
accessories such as trailer pump-off systems or
central tire inflation, the air for these accessories
must by-pass the dryer.
F. Refer to Symptom 6.
E. If vehicle uses Holset compressor, inspect
feedbackcheckvalveforproperinstallationand
operation.
G. Refer to Symptom 1.

12
DRM™/AD-IS®AIR DRYER TROUBLESHOOTING CHART (Continued)
SYMPTOMS CAUSE REMEDY
C. Refer to Symptom 1, Remedy B.
D. Repairorreplacepurgevalveassembly.
E. Checkgovernoratboth“cut-in”and“cut-out”
positionfor (i) proper pressures and (ii)
excessive leakage at fittings and exhaust.
F. Repairorreplacepurge valve assembly.
C. DefectiveAD-IS®air
dryerdeliverycheck
valve.
D. LeakingTurboCutoff
valve.
E. Defectivegovernor.
F. Leaking purgevalve
controlpistonquad-ring.
B. System pressure too
high (>135 p.s.i.)
C. Excessivepressure
pulsationsfrom
compressor. (Typical
single cylinder type).
D. Safetyvalve setting too
low (<150 p.s.i.)
A. Test to determine if air is passing through check
valve.Repair or replace. Refer to Symptom 1,
Remedy B.
B. Testwithaccurategauge.Replacegovernorif
necessary.
C. Increase volume in discharge line. This can be
accomplished by adding a 90 cubic inch (or
larger)reservoirbetweenthecompressorandthe
AD-IS®airdryer.
D. Replacesafety valve.
3. Safetyvalveonairdryer
“poppingoff”or
exhaustingair.
A. DefectiveAD-IS®air
dryerdeliverycheck
valve.
4. Constantexhaustofair
atairdryerpurge valve
exhaust or unable to
build system pressure.
(Chargemode.)
A. With compressor loaded, apply soap solution
onpurge valve exhaust, to test for excessive
leakage.Repairorreplacepurgevalveas
necessary.
B. Refertoparagraph5ofOperationandLeakage
Tests for heater and thermostat test.
A. Airdryerpurgevalve
leakingexcessively.
B. Purgevalvefrozenopen
-faultyheater and
thermostat,wiring,
blownfuse.

13
DRM™/AD-IS®AIR DRYER TROUBLESHOOTING CHART (Continued)
SYMPTOMS CAUSE REMEDY
B. Excessive bends in
dischargeline(water
collectsand freezes).
C. Pressureprotection
valve(s)inairdryerwill
notopen.
D. Refer to Symptom 4.
E. Refer to Symptom 7.
B. Discharge line should be constantly sloping from
compressor to air dryer with as few bends as
possible.
C. Replaceair dryer (pressure protection valvesare
notserviceable).
D. Refer to Symptom 4, RemedyA.
E. Refer to Symptom 7, RemediesAthrough D.
5. Can not build system
airpressure. A. Kinked orblocked
(plugged)dischargeline. A. Check to determine if air passes through
discharge line. Check for kinks, bends,
excessive carbon deposits, or ice blockage.
6. Airdryerdoesnot purge
or exhaust air. A. Faultyairdryerpurge
valve.
B. See Causes, B, E, and
G for Symptom #4.
A. Afterdeterminingairreachespurgevalvecontrol
port by installing aT-fitting with a pressure
gaugeintothegovernorunloaderport,repair
purgevalveifnecessary.
B. Refer to Symptom 4, Remedies B, E, and G.
Also refer to Symptom 1, Remedy B.
7. Desiccantmaterial
beingexpelledfromair
dryerpurgevalve
exhaust (may look like
whitish liquid or paste
or small beads.)
A. Faultydryercartridge.
B. Excessivedryervibration.
A. ReplaceAD-IS®air dryer cartridgeand/or
AD-IS®airdryer.
B. Checkreservoirmountingforloosenessor
damage. Repairmountingandreplacecartridge.
8. Unsatisfactory
desiccant life. A. Excessive system
leakage.
B. Wrongvehicleapplication
forAD-IS®air dryer.
C. Compressorpassing
excessive oil.
A. Refer to Symptom 1, RemedyA.
C. Check for proper compressorinstallation; if
symptoms persist, replace compressor. Refer to
BendixAdvancedTroubleshootingGuideforAir
BrakeCompressors(BW1971).
A. A slight “pinging” sound may be heard during
system build up when a single cylinder
compressor is used. If this sound is deemed
objectionable, it can be reduced substantially by
increasingthedischargelinevolume.
This can be accomplished by adding a 90 cubic
inchreservoirbetweenthecompressorand the
AD-IS®airdryer.
9. “Pinging”noise
excessiveduring
compressorloaded
cycle.
B. Refer to Symptom 2, Remedy C.
A. Singlecylinder
compressorwithhigh
pulse cycles.

14
A. Compressorfailsto
“unload”.
10. The airdryer purge
piston cycles rapidly in
thecompressor
unloaded(non-
compressing)mode.
A. Checkairhosefromgovernortocompressorfor
a missing, kinked or restricted line. Install or
repairairhose.
Repairor replace compressor unloader.
DRM™/AD-IS®AIR DRYER TROUBLESHOOTING CHART (Continued)
SYMPTOMS CAUSE REMEDY

15

16 BW1948 © 2007 Bendix Commercial Vehicle Systems LLC All rights reserved. 3/2007 Printed in U.S.A.