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Service bulletin SF631

A bulletin is a manufacturer's communication to its dealers, as NHTSA indexes it. The summary is NHTSA's. The document is the manufacturer's: read it at NHTSA. A bulletin is not a recall, and listing a model year does not mean every vehicle of it is concerned.

The communication, as NHTSA indexes it (as of 2026-10-19)
TypeService bulletin
NHTSA id10199364
Published by NHTSA2021-07-22
Manufacturer's numberSF631
Manufacturer's date2021-07-01
NHTSA componentENGINE AND ENGINE COOLING

NHTSA's summary

Field Service Campaign for Detroit Diesel Engine Fan Activation with A/C. On certain Freightliner and Western Star vehicles with Detroit Diesel engines, the engine fan fails to activate when the A/C pressure switch circuit is opened, resulting in poor A/C cooling performance at idle.

The document

The document is the manufacturer's. This site does not hold it. NHTSA files a document at one of these two addresses; we have not asked NHTSA which.

Components

Engine

Vehicles listed
FREIGHTLINER 108SD2022
FREIGHTLINER 114SD2022
FREIGHTLINER 122SD2022
FREIGHTLINER BUSINESS CLASS M22022
WESTERN STAR 47002022
WESTERN STAR 49002022
WESTERN STAR 57002022

Listing a model year does not mean every vehicle of it is concerned: the document says which.

Other bulletins for the same vehicles and component
CXA 03_26_Surge Tank2026-04-02. Other. CX Advocate for discolored coolant surge tanks (24CSA-20)
FleetCom_Heater Core2026-01-08. Other. Fleet Communications for Heater Core Plugging
TSB54-377-FTL2026-01-07. Service bulletin. Technical Service Bulletin Low Coolant Sensor
CXA_10_25_Conmet Oil Pan2025-11-05. Other. CX Advocate for ConMet Oil Pan Insert Additional Issues
CXA_9_25_Tech Questions2025-10-03. Other. CX Advocate for technical questions/issues raised
CXA_8_25_Tech Questions2025-09-02. Other. CX Advocate for technical questions/issues raised
24CSA-19Rev2025-09-02. Other. Revised Customer Service Annoucement for No Trouble Found Heavy Duty Engine Product (HDEP) Oil Separator Leaks
CXA 4_25_DPF Outlet Temp2025-05-02. Other. CX Advocate for DPF Outlet Temp High Gen5 DD15 ENGINES
CXA 3_25_NOx2025-04-02. Other. CX Advocate for NOx conversion low faults
CXA 3_25_DPF Outlet Temp2025-04-02. Other. CX Advocate for DPF Outlet Temp High Gen5 DD15 ENGINES