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Service Bulletin No. 2790
102D3, 102DL3
Product Improvement
04 - Brakes & Air System
Jul 11, 2001


Parts may be purchased from MCI Service Parts, Louisville, Kentucky or from MCI Service Parts, Newcastle, Ontario.
PDF Download - Click on file ->2790.pdf


Effective with unit number 53455, MCI has made design changes to the AD9 Bendix air dryer installation, adding a ball valve and a PuraGuard filter.

The PuraGuard filter functions as a filtration device for air entering the supply reservoir. The ball valve is used to bypass the air dryer and PuraGuard filter in the event of an air line freeze-up. The bypass valve can be manually set by the operator, restoring air supply and allowing the safe return of the coach to the garage.

The emergency bypass valve is for short term use only, due to unprocessed air entering the supply reservoir.



Qty.__New P/N__Description

1___4L-7-129__PuraGuard Bypass Retrofit Kit
______________Kit contents are:

__1___ 4L-19-210__PuraGuard bypass assembly

__2___ 19-1-1095__ Capscrew, hex, 5/16-18 x 1 inch, SS

__1___ 19-10-1472__ Elbow, male, 3/4 inch T, 1/2 inch MPT

__2___ 19-10-1495__ Fitting, straight, 3/4 inch NT, 1/2 inch MPT

__2___ 19-10-1684__ Elbow, 90 degree, 3/4 inch NT, 3/4 inch MPT

__1___ 19-10-2283__ Fitting, 3/4 C tube, 1/2 inch MPT

__1___ 19-10-544__ Tee fitting, 1/2 inch FPT

__8___ 19-11-258__ Tyrap

__9___ 19-11-259__ Tyrap

__3___ 19-12-27__ Grommet, 7/8 inch ID.

__1___ 19-12-4__ Grommet, 3/8 inch ID.

__2___ 19-2-198__ Lockwasher, 5/16, SS

__4___ 19-2-62__ Flatwasher, 5/16, SS

__ 2___ 19-3-314__ Hexnut, 5/16-18, SS

__ 2.3 ft._ 21-7305-5__ Pipe insulation, 7/8 inch ID x 3/8 wall

__26 ft._ 24-54-0011__ Pipe, tube, 7/8 inch ID x 3/8 wall

__1___ 4L-10-16__ Decal, air dryer

__a/r_ 21-7203-2__ Sealant

__1___7L-13-4038__Air Dryer Bypass Switch Kit
__________________Kit contents are:

____2___ 19-1-632__ Screw, #10-24 x 3 / 8 inch

____1___ 19-11-258__ Tyrap

____1___ 19-11-322__ Connector, water tight

____6___ 19-11-569__ Tyrap

____2___ 19-2-48__ Lock washer, #10

____4___ 19-2-7__ Washer, flat, #10

____1___ 4L-19-211__ Plate, switch, bypass valve

____1___ 7K-8-209__ Switch

____1___ 7L-12-3281__ Harness, Air Dryer Bypass

____1___ 7L-13-4067__ Schematic, Air Dryer Bypass

1___7L-14-0145__Electrical Installation Kit, Air Dryer Bypass
_______________Kit contents are:

__1___7L-8-3658__Tell tale light, air dryer bypass

__1___ 3L-1-1573__Plug, snap-in




Service Information:

1. New parts will be available for service replacement.

Service Procedure:

General notes

Read this entire procedure before beginning work.

Use Safe Shop Practices At All Times.

1. Turn the main battery disconnect switch to OFF.

2. Open the LH, front side service compartment door. Pull the front bumper release handle to access the spare tire compartment ( Figure 1 ). Carefully remove the spare tire to gain access to the spare tire compartment.

Figure 1. Front bumper release handle.

3. On the rear wall of the spare tire compartment, use a pencil and tape measure to mark the center of the three air line holes, 1.5 inches from the bottom of the angle ( Figure 2 ). Mark intersecting lines ensuring 2.0 inches between the centers of the holes. Using a 1 1/4 ( 1.25 ) inch hole saw, cut three holes ( located on the back wall of the spare tire compartment ) at the intersection of the lines. Install grommets ( part number 19-12-27 ) into the three holes.

Figure 2.

4. Open the front, side service door. Using a tape measure, mark a line 9.0 inches from the outer wall, and 13.0 inches from the floor, on the rear wall of the compartment. Position the PuraGuard bypass assembly ( part number 4L-19-210 ) on the rear wall, with the RH bracket hole centered over the intersection of the two lines ( Figures 3, 4, and 5 ).

Figure 3.

5. Using the bracket of the PuraGuard bypass assembly as a template, mark two holes. Place the PuraGuard bypass assembly aside and drill the two holes using a 11 / 32 inch diameter drill bit.

Note: Use a drill bit depth gauge to avoid damage to other components.

6. Mount the PuraGuard bypass assembly to the compartment wall using the two capscrews ( part number 19-1-1095 ), four flat washers ( part number 19-2-62 ), two lock washers ( part number 19-2-198 ), and the two hex nuts ( part number 19-3-314 ) ( Figure 4 ).

Figure 4. PuraGuard bypass assembly.

7. Using a 5/8 inch drill bit, drill a hole through the floor ( approximately 2 1/4 inches from the back wall ) in line with the drain tube. Install the grommet ( part number 19-12-4 ) into the hole. Position the drain tube through the grommet ( Figure 5 ).

8. Slide the switch plate ( part number 4L-19-211 ) over the valve handle. Install the switch plate to the valve using the two screws ( part number 19-1-632 ), four flat washers ( part number 19-2-7 ) and two lockwashers ( part number 19-2-48 ) ( Figures 4 and 5 ).

Note: To ensure proper alignment between the valve and the switch plate, the flat washers ( which function as shims ) must be installed between the switch plate and the valve.

Figure 5.

9. Raise the coach to the desired height. Position jackstands at the front and rear frame support points, according to Figures 6 and 7, to ensure that the coach is securely supported before attempting work underneath the coach.

Note: Refer to Section 3G / Jackstand Support Points, in the MCI 102D Series Maintenance Manual, for the basic rules, procedures and safety precautions that must be followed before a coach is to be lifted.

10. Locate the air line from the air dryer delivery port to the wet tank. Remove and discard the air line.

11. Remove the insulation over the copper tube ( air dryer supply line ) ( Figure 8 ). Cut the copper tube, 3 inches below the tunnel floor.

12. Remove the existing elbow at the supply port of the air dryer. Install the elbow ( part number 19-10-1684 ) at the supply port of the air dryer ( Figures 8 and 9 ).

13. On a workbench, pre-assemble the two fittings ( part number 19-10-1495 ), the tee fitting ( part number 19-10-544 ), and the copper tube connector fitting ( part number 19-10-2283 ) ( Figure 8 ).

Note: Apply sealant ( part number 21-7203-2 ) to the threads, before assembly.

Figure 8.

14. Cut a 1 foot piece off of the nylon tube ( part number 24-54-0011 ). Install the tube into the bottom of the tee assembly and connect the tube to the elbow, installed in Step 12. Connect the copper tube connector to the copper line.

15. Cut the nylon tube ( part number 24-54-0011 ) into three pieces, 7 feet, 8 feet and 10 feet.

16. Install the nylon tube ( 7 feet long ) from the tee connector to the PuraGuard assembly, at location " A " ( Figures 9 and 12 ).

17. Install the nylon tube ( 8 feet long ) from the delivery port of the air dryer to the PuraGuard assembly, at location " B " ( Figures 9 and 12 ).

Figure 9.

18. Install the nylon tube ( 10 feet long ) from the delivery port of the PuraGuard assembly to the wet tank, at location " C " ( Figure 10 ).

Figure 10.

19. In the spare tire compartment, secure the nylon tubes using tyraps ( part number 19-11-259 ) ( Figure 11 ).

Figure 11.

20. Route the tubes up and around the fresh air intake. Using three tyraps ( part number 19-11-259 ), secure the tubes to the existing harnesses and airlines ( Figure 12 ).

Figure 12.

21. Install the insulation ( part number 21-7305-5 ) over the air dryer supply line and elbow ( Figure 8 ).

22. Lower the coach to the ground.

23. Open the LH front side service compartment door. Using a clean cloth and isopropyl alcohol, wipe clean the area where the air dryer decal is to be applied ( Figures 5 and 12 ).

Note: Allow 10 minutes for isopropyl to flash off.

24. Apply the PuraGuard bypass decal ( part number 4L-10-16 ), 3.50 inches from the outer wall and 5.00 inches from the floor ( Figures 5 and 12 ).

25. Using an allen key, remove the four screws from the LH switch panel, in the drivers compartment.

Figure 13.

Note: The harness ( part number 7L-12-3323 ) will be routed from the ADBP switch located in the front, side service compartment to the air dryer bypass telltale light installed in the drivers instrument panel. One end of the harness will have routed up through the electrical junction box to the drivers instrument panel. The other end of the harness will have to be routed down through the electrical junction box to the front, side service compartment.

Note: The air dryer bypass telltale light should be installed in one of two designated locations, either a blank plug in the LH switch panel or in the blank plug beside the windshield wiper controls ( Figure 13 ). If the telltale is to be installed in the location beside the windshield wiper controls, the existing snap-in plug will have to be discarded and replaced with the plug provided in the parts list.

26. Open the front junction box door, located on the roadside of the coach. Feed a fish wire up through the harness tunnel in the front junction box, leading up to the LH switch panel ( Figure 14 ).

Figure 14.

Note: If the telltale is to be installed in the location beside the windshield wiper controls, then the instrument panel will have to be pulled forward to route the harness. Use an allen key to remove the eight screws from the instrument panel, to allow the panel to be pulled forward.

27. Route harness ( part number 7L-12-3323 ) from the electrical junction box so that:

a. wire 55BP ( with #10 ring terminal ) is routed to Stud 55,

b. wire 36BP ( with #10 ring terminal ) is routed to ground studs,

c. wires ADBP and 55BP ( with fast-on terminals ) are routed up to the blank telltale location,

d. wires 36 BP and ADBP ( with #8 ring terminal ) are routed down to ADBP switch.

28. Attach the end of the harness ( wires ADBP and 55BP ) to the fish wire, and pull the harness up into the drivers compartment through the LH switch panel ( Figure 14 ).

29. Secure wires 55BP and ADBP ( using fast-on terminal ) to the telltale. Secure the telltale into plug.

30. In the front side service compartment, remove the switch housing from the switch on the air dryer bypass control lever, by removing the two screws on top of the switch. Feed the harness through the water tight connector ( part number 19-11-322 ) and secure wires 36BP and ADBP ( using ring terminals ) to the NC and C contacts on the switch.

31. Re-install the switch housing on the switch, using the two screws removed in Step 28. Tighten the water tight connector.

32. Install the switch ( part number 7K-8-209 ) to the switch plate, mounted on the valve assembly, using the two screws ( part number 19-1-720 ), two lockwashers ( part number 19-2-83 ) and two nuts ( part number 19-3-26 ) ( Figure 5 ).

33. Secure wire 55BP ( using ring terminal ) to Stud 55 ( Figure 14 ).

34. Using tyraps ( part number 19-11-569 ), secure the harness every six to eight inches.

35. Re-install the LH switch panel.

36. Turn the main battery disconnect switch to ON position.

37. Turn the valve handle on the air dryer pass assembly to the " bypassed " position. Enter coach and verify that the telltale is illuminated on the instrument panel.

Note: If the telltale is not illuminated, turn the main battery disconnect switch back to the OFF position and verify installation.

38. Once installation is complete and verified, turn the valve handle back to the normal position.

39. Secure the handle into position using a tyrap ( Figure 5 ).

Procedure complete.
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