BENDIX R-12DC DBL CHECK RELAY VALVE Manual Download Page 4

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*Crack Pressure is the amount of control
pressure required by the valve to initiate
air delivery.  For Crack pressures other
than 4 psi, a differential spring is used in
the assembly to produce the required
valve response.
(Models designed to have a 4 psi crack
pressure do not require a differential spring.)

Key No.

DESCRIPTION

1

VALVE COVER

2

VALVE SPRING

3

CHECK VALVE GUIDE

4

CHECK VALVE

5

O-RING

6

DOUBLE CHECK COVER

7

O-RING

8

O-RING

9

RELAY PISTON

10

VALVE BODY

11

INLET & EXHAUST VALVE

12

VALVE RETAINER

13

SPRING

14

O-RING

15

O-RING

16

EXHAUST COVER

17

RETAINING RING

18

DIFFERENTIAL SPRING (IF USED)

PRIMARY CONTROL

PORT 1/4 NPT

SECONDARY

CONTROL PORT

 1/4 NPT

16

CAP SCREW

2

1

10

11

CAP

SCREW

3

4

5

6

7

9

8

DIFFERENTIAL SPRING

(CONTROLS CRACK PRESSURE*)

(NOT REQUIRED FOR MOST

MODELS.

SEE BELOW.)

17

15

14

13

12

VERTICAL
DELIVERY

PORTS

SUPPLY

PORT

HORIZONTAL

DELIVERY

PORTS

DIFFERENTIAL SPRINGS

FIGURE 7 - R-12DC

 EXPLODED VIEW

1. Remove the four cap screws securing the mounting

bracket and cover to the body.  Retain the cap screws
for reuse.

2. Discard the mounting bracket.

3. Remove and discard sealing ring (7) from the cover (1).

a. Remove the 2 torx screws securing the double check

cover (6) to the cover (1).

b. Remove the double check cover (6) from cover (1)

and remove and discard spring (2), guide (3), double
check diaphragm (4), and o-ring (5).

4. Remove and discard sealing ring (7) from the cover (1),

and mounting bracket.

Caution: Drain all reservoirs before attempting to remove
the inlet exhaust valve.

DISASSEMBLY

Note: Prior to disassembly, mark the location of the
mounting bracket to the cover and the cover to the body.

CAUTION: The valve body may be lightly clamped in a bench
vise during disassembly, however, over-clamping will result
in damage to the valve and result in leakage and/or
malfunction.  If a vise is to be used, position the valve so
that the jaws bear on the supply ports on opposing sides of
the valve’s body.

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Summary of Contents for R-12DC DBL CHECK RELAY VALVE

Page 1: ...LVE MODEL WITH 4 VERTICAL DELIVERY PORTS EXTERIOR R 12DC VALVE MODEL WITH 2 HORIZONTAL AND 2 VERTICAL DELIVERY PORTS PRIMARY SERVICE PORT FIGURE 2 R 12DC RELAY VALVE WITH BIASED DOUBLE CHECK SECTIONAL...

Page 2: ...e will move shutting off the primary service line and instead allow the secondary service line to apply the air pressure needed to operate the valve Note Secondary service line may leak out of the pri...

Page 3: ...ded if intrusive maintenance is performed during the warranty period No two vehicles operate under identical conditions as a result maintenance intervals may vary Experience is a valuable guide in det...

Page 4: ...NTAL DELIVERY PORTS DIFFERENTIAL SPRINGS FIGURE 7 R 12DC EXPLODED VIEW 1 Remove the four cap screws securing the mounting bracket and cover to the body Retain the cap screws for reuse 2 Discard the mo...

Page 5: ...cover assembly 16 2 Install o ring 8 on piston 9 3 Install sealing ring 7 on cover 1 4 Install retainer 12 on inlet exhaust valve 11 and insert both in the body 10 5 Install spring 13 in the body 10 6...

Page 6: ...R R 12DC RELAY VALVE COMPRESSOR FIGURE 8 TYPICAL PIPING SCHEMATIC DC 4 DOUBLE CHECK VALVE ANTI COMPOUND LINE GAUGE SR 1 SPRING BRAKE VALVE SERVICE BRAKE VALVE SPRING BRAKES PARKING VALVE ABS ECU MODUL...

Page 7: ...he 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 deac...

Page 8: ...8 BW1933 2007 Bendix Commercial Vehicle Systems LLC All rights reserved 3 2007 Printed in U S A...

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