NHTSA ID Number: 11022458
Manufacturer Communication Number: SB777-3
TSB/Document Date: 2025-09-03
Summary
Thermo King
has introduced a new belt-tensioning tool. The Continental™ TensionRite Belt Frequency Meter. This tool measures the belt frequency with high accuracy and easy operation. This bulletin serves as guide for the specification and best practices of tensioning belts for all units.
Service Bulletin
SB777-3
Date:
14 August 2025
Subject:
SB777–3 - Belt Tension Guidelines
B u l l e t i n L o c a t i o n : e–Tech Library
Units Covered In This Bulletin:
Trailer Units
Truck Units
APU Units
Precedent S-750i
T-80 Series
TriPac Evolution
ADVANCER S-DRC
T-90 Series
TriPac 3
Heater Units
Heat King
SLXi LOCAL and DRC
Precedent S and C Series
SB Series
All Thermo King Units equipped with drive belts.
Comments:
Thermo King has introduced a new belt-tensioning tool. The Continental™ TensionRite Belt
Frequency Meter. This tool measures the belt frequency with high accuracy and easy operation.
This bulletin serves as guide for the specification and best practices of tensioning belts for all
units.
I m p o r t a n t : See the unit specific Maintenance Manual for detail belt service procedures.
I m p o r t a n t : The Maintenance Manuals will be updated with this bulletins information upon the
next revision.
I m p o r t a n t : VIDEO LINK: Continental™ TensionRite Belt Frequency Meter Video Link
Figure 1. Aftermarket PN: 2043185
1
Service Bulletin
SB777-3
Belt Tension Best Practices:
Belt tension should be checked and adjusted if found out of specification during routine
maintenance. Following Thermo King Specifications for belt tension adjustment will maximize
unit reliability.
Belt tension must be set properly to avoid accelerated belt wear or early component failure.
Over tensioned belt can cause: Early bearing, component, or belt failure. Under tensioned belts
can cause: belt failure and/or component slippage. Refer to the maintenance manual for proper
settings. Note that the P6K poly-V belt design is more sensitive to over-tensioning than the Vbelts used in the past.
During belt replacement, it is important to evaluate bearing condition. With belt removed spin
component pulleys. Rotate the fan shafts, alternator, generator, and/or idler pulleys by hand.
Inspect Belt Driven Components:
•
Pulleys should spin freely and smoothly.
•
Bearings should maintain concentric position without movement. Move the pulleys radially
to confirm that bearing clearances are tight, with no more than 0.005” movement.
•
Listen for noises as the pulley is rotated and investigate squeaking or rubbing sounds.
Roughness, looseness, or abnormal noises can indicate problems, such as a failing bearing.
•
Replace damaged components as needed to assure reliable operation.
Inspect for Belt Wear:
•
Glazing
•
Broken belt ribs and cracks
•
Frayed edges (possible misalignment of pulleys)
•
Replace as necessary
2
Service Bulletin
SB777-3
T-80 Unit Belt Information
Table 1. T-680R/T-880R/T-1080R
Lbs. Tension Using Commercially
Available Tool
Belt
Water Pump Belt
Engine/Electric Motor (Jackshaft)
Electric Motor (Jackshaft)/Compressor
Frequency Gauge P/N 2043185
Setting Where Applicable
New Belt
Field Reset
New Belt
Field Reset
40 lbs.
32 lbs.
126 Hz
118 Hz
—
—
62 Hz
55 Hz
Automatically tensioned by tensioner position. Refer to the “Belts” information in the
Maintenance Manual.
Table 2. T-680S/T-880S/T-1080S
Belt
Lbs. Tension Using Commercially
Available Tool
Water Pump Belt
Engine/Electric Motor (Jackshaft)
Electric Motor (Jackshaft)/Compressor
Frequency Gauge P/N 2043185
Setting Where Applicable
New Belt
Field Reset
New Belt
Field Reset
40 lbs.
32 lbs.
126 Hz
118 Hz
—
—
62 Hz
55 Hz
Automatically tensioned by tensioner position. Refer to the “Belts” information in the
Maintenance Manual.
Table 3. T-1080S SPECTRUM
Belt
Lbs. Tension Using Commercially
Available Tool
Water Pump Belt
Engine/Electric Motor (Jackshaft)
Electric Motor (Jackshaft)/Compressor
Table 4.
Frequency Gauge P/N 2043185
Setting Where Applicable
New Belt
Field Reset
New Belt
Field Reset
40 lbs.
32 lbs.
126 Hz
118 Hz
—
—
52 Hz
45 Hz
Automatically tensioned by tensioner position. Refer to the “Belts” information in the
Maintenance Manual.
T-1280R SPECTRUM
Belt
Water Pump Belt
Engine/Electric Motor (Jackshaft)
Electric Motor (Jackshaft)/Compressor
Lbs. Tension Using Commercially
Available Tool
Frequency Gauge P/N 2043185
Setting Where Applicable
New Belt
Field Reset
New Belt
Field Reset
40 lbs.
32 lbs.
126 Hz
118 Hz
—
—
69 Hz
55-60 Hz
Automatically tensioned by tensioner position. Refer to the “Belts” information in the
Maintenance Manual.
3
Service Bulletin
SB777-3
Figure 2. T-680R and T–880R Units
2
1
RAJ811
Figure 3.
T-1080R Units
2
1
RAJ810
1.
Engine Belt Tension Check Location
2.
Compressor Belt Tension Check Location
4
Service Bulletin
SB777-3
Figure 4.
T-680S, T-880S, and T-1080S
2
1
RAJ812
Figure 5.
T-1080S SPECTRUM
2
1
RAJ846
Figure 6.
T-1280R SPECTRUM
2
1
RAJ813
1.
Engine Belt Tension Check Location
2.
Compressor Belt Tension Check Location
5
Service Bulletin
SB777-3
T-90 Unit Belt Information
I m p o r t a n t : After installing new belts, the unit must be run for 20 minutes after the belt is
tensioned properly. After the 20 minute break in, re-tension the belts to the “new belt
tension specification”. See the maintenance manual for the proper procedure.
Unit
Belt
Initial, New Belt Tension
(Less Than 1 hr. Run Time)
Break-In / Field Reset Tension
(More Than 1 hr. Run Time)
ALL
Water Pump
Belt
126 Hz (40 lbs)
118 Hz (32 lbs)
Compressor
(6 Rib Belt)
156 +/- 4 Hz
134 +/- 8 lbs.
139–156 Hz
90–139 lbs.
Engine Belt
(3 Rib Belt)
61 +/- 6 Hz
119 +/- 12 lbs.
59–68 Hz
106–144 lbs.
Compressor
(6 Rib Belt)
139 +/- 4 Hz
138 +/- 8 lbs.
125–139 Hz
99–138 lbs.
Engine Belt
(3 Rib Belt)
63 +/- 6 Hz
132 +/- 12 lbs.
60–64 Hz
118–135 lbs.
Compressor
(6 Rib Belt)
150 +/- 4 Hz
147 +/- 8 lbs.
137–150 Hz
109–147 lbs.
62 +/- 6 Hz
149 +/- 12 lbs.
58–59 Hz
133–135 lbs.
T-590
T-690
Tool Used
T-890
T-1090
Units Built
Before June
2nd 2025
and SB995
Update NOT
Performed)
Engine Belt
(3 Rib Belt)
RECOMMENDED:
Hz - TK Belt Tension Tool
2043185
TEMPORARY:
Setting Tension in Lbs.
with Commercially
Available Tool
See notes below
T-1090
Units Built
After June
2nd 2025 or
SB995
Update
Performed)
T-1090
SPECTRUM
Compressor
(6 Rib Belt)
176 +/- 4 Hz
165–169 Hz
Engine Belt
(3 Rib Belt)
62 +/- 6 Hz
58–59 Hz
Compressor
(6 Rib Belt)
149 +/- 4 Hz
144 +/- 8 lbs.
135–143 Hz
106–132 lbs.
Engine Belt
(3 Rib Belt)
46 +/- 4 Hz
148 +/- 12 lbs.
44–54 Hz
132–201 lbs.
Note: The most accurate and recommend way to set belt tension is to measure and set the tension Hz with tool 2043185.
Note: Using a commercially available tool to set belt tension in lbs. may reduce belt life and should only be used as a temporary setting until
tool 2043185 can be used. This does not apply to the coolant pump belt.
6
Service Bulletin
SB777-3
Figure 7.
Tension Check Locations - Single Temperature Units
2
1
RAJ664
Figure 8. Tension Check Locations - Multi-Temperature Unit
2
1
RAJ678
1.
Engine Clutch
2.
Compressor Pulley
7
Service Bulletin
SB777-3
SLXi LOCAL and SLXi-DRC Unit Belt Information
Table 5. SLXi LOCAL and SLXi DRC
Belt
Specification
Engine/Cross Shaft (Jackshaft) Belt
New Belt and Field Reset:Use service tool P/N 2042436 to set belt tension to a distance of 139.0
mm.
See the service procedure.
New Belt:
106-118 Hz - TK Belt Tension Tool 2043185
Fan Drive Belt
Field Reset:
95-106 Hz - TK Belt Tension Tool 2043185
New Belt:
126 Hz - TK Belt Tension Tool 2043185
Water Pump Belt
Field Reset:
118 Hz - TK Belt Tension Tool 2043185
Figure 9.
1
SLXi LOCAL and SLXi DRC
2
1.
Tension Check Location
2.
Tension Check Location
8
RAJ814
Service Bulletin
SB777-3
ADVANCER S-DRC Belt Information
Table 6.
ADVANCER S-DRC
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TSB/Document ID: SB777-3
Replacement Service Bulletin Number:
MFR Communication Date: 2025-08-14
MFR Internal Campaign ID/Software Version:
Communication Type: Service Bulletin/Repair Instructions
NHTSA Components: ENGINE
MFR Component System:
MFR Component Subsystem:
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