Bendix® GSAT® (Global Scalable Air Treatment) Air Dryer Heater Kit
for Daimler® Truck North America (DTNA)
KIT COMPONENTS

GENERAL SAFETY GUIDELINES

The following component is in the Bendix® GSAT® (Global
Scalable Air Treatment) air dryer heater kit for Daimler®
Truck North America (DTNA):
Item No.

Component

Quantity

1

Heater 12V

1

Bendix Kit Part Number: K279104K57

NOTE: Image shown without air dryer cartridge. For most vehicles, it
is not necessary to remove the air dryer cartridge in order to replace
the air dryer heater.
Figure 1 – GSAT Air Dryer Heater Kit

VEHICLE PREPARATION
1. Park the vehicle on a level surface and chock the wheels.
2. Turn the ignition switch OFF.
3. Drain all reservoirs to 0 psi (0 kpa).
4. Clean the exterior of the air dryer body, cartridge, core
module, and core module silencer(s) to remove any
dirt and debris.

Always depressurize the air dryer and all other
reservoirs on the vehicle to 0 psi (0 kpa) before servicing
the air dryer. Failure to drain the air pressure from the
air dryers and all other reservoirs may result in property
damage, serious injuries, and/or death.

WARNING! PLEASE READ AND
FOLLOW THESE INSTRUCTIONS
TO AVOID PERSONAL INJURY OR DEATH:

When working on or around a vehicle, the following
guidelines should be observed AT ALL TIMES:
▲Park the vehicle on a level surface, apply the parking
brakes and always block the wheels. Always wear personal
protection equipment.
▲Stop the engine and remove the 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.
▲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.
▲If the work is being performed on the vehicle’s air brake
system, or any auxiliary pressurized air systems, make
certain to drain the air pressure from all reservoirs before
beginning ANY work on the vehicle. If the vehicle is
equipped with a Bendix® AD-IS® air dryer system, a Bendix®
DRM™ dryer reservoir module, a Bendix ® AD-9si ®, AD-HF®,
or AD-HFi ® air dryer, be sure to drain the purge reservoir.
▲Following the vehicle manufacturer’s recommended
procedures, deactivate the electrical system in a manner
that safely removes all electrical power from the vehicle.
▲Never exceed manufacturer’s recommended pressures.
▲Never connect or disconnect a hose or line containing
pressure; it may whip and/or cause hazardous airborne
dust and dirt particles. Wear eye protection. Slowly open
connections with care, and verify that no pressure is
present. Never remove a component or plug unless you are
certain all system pressure has been depleted.
▲Use only genuine Bendix ® brand replacement parts,
components and kits. Replacement hardware, tubing, hose,
fittings, wiring, etc. must be of equivalent size, type and
strength as original equipment and be designed specifically
for such applications and systems.
▲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.
▲Prior to returning the vehicle to service, make certain all
components and systems are restored to their proper
operating condition.
▲For vehicles with Automatic 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.
▲The power MUST be temporarily disconnected from the
radar sensor whenever any tests USING A DYNAMOMETER
are conducted on a vehicle equipped with a Bendix ®
Wingman ® system.
▲You should consult the vehicle manufacturer's operating
and service manuals, and any related literature, in
conjunction with the Guidelines above.

1

DISASSEMBLY

ASSEMBLY

NOTE: This maintenance kit does not typically require
removal of the air dryer from the vehicle; however, if removal
is necessary, adhere to the following caution.

1. Slide the heater assembly into the body, making certain
not to damage the seals.

While performing service on the GSAT air dryer, do not
use a clamping device directly on any die cast aluminum
component as damage may result. Instead, install a fitting
in the supply port and clamp the fitting into a vise. For
replacement kit part numbers and instructions, refer to
S-1706, Bendix® GSAT® (Global Scalable Air Treatment)
Air Dryer Replacement Kits for Daimler® Truck North
America (DTNA), on B2Bendix.com.

NOTE: Typically, there is an alignment feature (a tab, lug,
or other) on the air dryer body assembly which aligns with
the heater assembly.
2. Secure the heater assembly to the air dryer body with the
mounting screw using a T-27, 6-lobe drive to a torque
of 28 in-lb (3.2 N•m). See Figure 2.

1. D
isconnect the vehicle wiring harness electrical connector
from the heater electrical connector on the body of the
air dryer. See Figure 1.
NOTE: Lift the locking tab on the vehicle wiring harness
connector BEFORE attempting to disconnect the connector.
2. Unscrew the mounting screw that secures the heater
assembly to the air dryer body using a T-27, 6-lobe drive.
3. Carefully pull the heater assembly straight out of the air
dryer body.
4. Discard the old heater.

Cleaning and Inspection
1. Using a clean rag, wipe the air dryer heater bore clean,
taking care to not knock contamination into the bore.
2. Inspect for physical damage to the body casting and
take note of broken or missing parts.

Figure 2 – Assembly

3. Inspect the visible parts of the air dryer for severe
corrosion, pitting, and cracks. Superficial corrosion
and/or pitting on the exterior portion is acceptable.

3. Connect the wiring harness to the heater assembly
on the dryer. Push the wiring harness onto the heater
connector until the connector stops and compress the
locking feature, thereby securing the harness in place.

4. Inspect the bore for deep scuffing, gouges, nicks, or
damage that would prevent proper operation.

4. Before placing the vehicle back into service, perform the
Operational Test.

NOTE: If any of the conditions in Steps 2 to 4 are noted, repair
the damage or replace the GSAT air dryer as necessary.
5. Inspect all air line fittings for corrosion. Clean, repair,
or replace corroded or damaged fittings as necessary.

IMPORTANT
Failure to maintain and replace corroded fittings may
result in poor vehicle performance and may be a violation
of commercial vehicle regulations.

2

NOTE: The heater only turns on in cold environments below
44 ± 12°F (7 ± 6°C).

OPERATIONAL TEST

TECHNICAL ASSISTANCE

Before placing the vehicle in service, perform the following
tests.

For additional assistance, the Bendix Tech Team can
be reached by email at [email protected] or by
phone at 1-800-AIR-BRAKE (1-800-247-2725), option 2.
Representatives are available Monday through Thursday,
8:00 a.m. – 6:00 p.m., and Friday, 8:00 a.m. – 5:00 p.m. ET.

1. Close all of the reservoir drain cocks.
2. Start the vehicle. With the engine at 1800 rpm, build
up system pressure to system cutout while observing
that both service reservoir dash gauges show a rise in
pressure from 0 psi (0 kpa) to system cutout. If either
gauge fails to display this condition, stop testing and
check the installation. Note that the GSAT system
regenerates/purges with an audible escape of air
when system cutout pressure is reached. Refer to
SD-24-250D, Bendix® GSAT® (Global Scalable Air
Treatment) System for Daimler® Truck North America
(DTNA), on B2Bendix.com for more information on
troubleshooting a GSAT system.
NOTE: The service reservoir pressures will drop slightly
during regeneration/purge.
3. Fan down the service brakes by repeatedly pressing
and releasing the service brakes to reduce system air
pressure to system cut-in. Note that the system – once
again – builds to full system pressure and is followed
by a regeneration/purge event at the GSAT air dryer
primary exhaust.
4. To verify proper park brake function, use the Hand Control
Unit (HCU) to release and apply the tractor park brakes
several times. The HCU and/or dash cluster should
illuminate, indicating a proper park state. Refer to the
applicable Operator's Manual for HCU statuses.
5. It is recommended that the following items be tested for
leakage to ensure the GSAT will not cycle excessively:
a. A
ir brake system (Refer to the Bendix® Air Brake
Handbook, BW5057, on B2Bendix.com)
b. Compressor unloader mechanism
c. GSAT core module pneumatic connections
d. D
rain cock and safety valve in first (supply) reservoir
(if equipped)
e. A
ll air connections leading to and from the first
(supply) reservoir (if equipped)

3

24/7/365 ACCESS
FULL SERVICE AT YOUR FINGERTIPS

1-800-AIR-BRAKE (1-800-247-2725)
TECHTEAM@BENDIX.COM

WEB-BASED TRAINING
LOG ON AND LEARN FROM THE BEST

Any references in this document to DAIMLER and any other company or trademark are solely for
identification and cross reference purposes. The trademarks are the property of their respective companies.
Unless otherwise indicated, the trademarks used in this document, including Bendix,
are United States trademarks owned by, or licensed to, Bendix Commercial Vehicle Systems LLC.

4

S-1703 Rev 000 © 4/2025 Bendix Commercial Vehicle Systems LLC, a member of Knorr-Bremse • All Rights Reserved