Service Bulletin
SB995-1
Date:

August 15, 2025

Subject:

T-1090 Single Temp. Harmonic Vibration Unit Update

Location:

e-Tech Library

Units:

T-1090 single temperature, self-powered truck units produced before June 2,
2025. Only units produced before June 2, 2025 with excessive harmonic vibration
are affected.

Description:

Firing frequencies of the engine and compressor are in close proximity to each
other and may create harmonic vibration concerns on some units. The
motor/jackshaft pulley, engine, and compressor belts included in kit 750025 along
with new SR-3 software D0B0 and HMI software 75C9 must be updated to
alleviate the vibration.
For unit coverage, contact your local commercial team with unit details.
This update will not be covered under warranty or campaign.

Labor Time:

2.5 Hours

Parts:

Kit 750025, includes:
Ref. #
1
2
3
-

Part Number
781669
772965
782094
941352

Description
BELT - engine to motor/ jackshaft (3-rib)
PULLEY - motor/ jackshaft
BELT - motor/jackshaft to compressor (6-rib)
Completion Label

1

Procedure:
1. Disconnect the unit battery and all electrical power sources from the unit.
2. Remove the top cover to access the belt area (if equipped).
IMPORTANT: Do not allow the alternator heat sink to contact other components during
service procedures. The heatsink can be damaged if it contacts other components
during service procedures.
3. Remove the single wire plug off the rear of the alternator.

4. Loosen alternator bolts 1, 2, and 3 shown below to relieve belt tension.
5. Remove and discard the 6-rib belt.
6. Remove bolts 1 and 2 shown below. Position alternator out of the way for access.

2

7. Remove the frame cross member located next to the coolant tank. Keep the cross member
and hardware for reinstallation.

8. Slightly loosen the engine belt tensioner lock nut (1).
9. Rotate the belt tensioner adjustment bolt (2) counterclockwise to raise the pulley and relieve
belt tension.

10. Remove and discard the motor/jackshaft to compressor 3-rib belt.

3

11. Mark the four corners of the motor or jackshaft mounting points on the frame with a paint pen
to aid in realignment.
12. Remove the four motor or jackshaft to frame mounting bolts.

13. Remove the four bolts securing the motor or jackshaft support bracket to the frame bracket
shown below.

14. Slide the motor or jackshaft assembly towards the front of the unit to gain access to the
motor or jackshaft pulley.
IMPORTANT: Do not allow fan blades to contact the radiator fins.
15. Remove and discard the motor or jackshaft pulley and hardware.

4

16. Verify the new motor or jackshaft pulley (PN 772965) has a key installed. Slide the new
pulley onto the motor or jackshaft shaft. Leave the pinch bolts loose for pulley alignment in a
later step.

17. Slide the motor or jackshaft back into position referencing the paint pen markings from step
11.
18. Install but do not tighten the four motor or jackshaft to frame bolts.

19. Install but do not tighten the four bolts securing the motor support bracket to the frame
bracket shown below.

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20. Use pulley alignment tool 2043191 to align compressor pulley to the motor / jackshaft pulley.
It may be necessary to loosen and adjust the four motor or jackshaft mounting points to
properly align the pulleys front to back and side to side.

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21. When the pulleys are in alignment torque the four motor or jackshaft mounting bolts to
specification: 24 ft-lbs (33 Nm) to lock it into position.

22. Torque the four bolts securing the support bracket to frame backet: 24 ft-lbs (33 Nm).

23. Torque the motor or jackshaft pulley split hub pinch bolts to 24 ft-lbs (33 Nm) to lock it onto
the shaft. Rotate the fan to verify it does not contact fan shroud.

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24. Install and properly route the new 3-rib engine belt (PN 781669).

25. Install the alternator. Leave all mounting hardware slightly loose. Reconnect the wire
connection removed in step 3.

8

26. Install and properly route the new 6-rib compressor / alternator belt (PN 782094).

9

27. Set the belt tension of the 3-rib engine belt first. Rotate the belt tensioner adjustment bolt (2)
clockwise to lower the pulley and increase belt tension. Use TK PN 2043185 Tension-Rite
frequency meter to check belt tension.
SPECIFICATION: 62 +/- 6 Hz
-

Set belt tension to initial specification at the location shown below:
Tighten the belt tensioner lock nut

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28. Set the belt tension of the 6-rib compressor belt. Rotate the alternator adjustment bolt (3) to
tighten the belt. Use TK PN 2043185 Tension-Rite frequency meter to check belt tension.
SPECIFICATION: 176 +/- 4Hz
- Set belt tension to the initial specification at the location shown below:
- Tighten the alternator mounting bolts.

29. Reinstall the cross member using the original hardware.

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30. Reconnect the unit battery and run the unit for 20 minutes.
31. After the 20-minute run time, turn the unit off and disconnect the battery.
32. Use TK PN 2043185 Tension-Rite frequency meter to recheck and adjust the tension of
BOTH belts to the Break-In Tension:
Belt
3-rib Engine Belt
6-rib Compressor Belt

Initial Tension
62 +/- 6 Hz
176 +/- 4 Hz

Break-In Tension
58-59 Hz
165-169 Hz

33. Verify all tensioner and alternator hardware is secure.

To connect Wintrac to a T-90 unit, the following components are needed:

Ref. #
1
2
3
4
5

Description
PC with Wintrac software
ADAPTER - serial port to USB
CABLE - data (15-pin D, 9-pin D PC)
ADAPTER - cable (15-pin D PC to 5-pin Deutsch)
Communication Cable (connects to J9 on SR-3 board)

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Part Number
N/A
420575
449417 (20 ft.) or 449418 (50 ft.)
2049018
415484

34. Update the base controller software to D0B0 using Wintrac; link here: A46A.
35. Update the HMI software to 75C9 as shown in CB779; link here: CB779.
36. In the HMI, navigate to Programable Features. Set the T-1090 Pulley Update to YES.

37. Set the engine RPM using procedure F11A; link here: F11A.
38. Clean the condenser plenum and apply the completion label TK PN 941352 where shown
below:

39. Reinstall unit top cover (if equipped).
40. Verify proper unit operation.

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