i-350 L5-3.5L (2006)
Seat Belt: All Technical Service Bulletins
Restraints - Seat Belt Locking Characteristics
TSB # IB07-11-S004
Issue Date: APRIL 2007
Subject:
Safety Belt Locking Conditions
Affected Vehicles:
2005-2007 Isuzu Ascender
2007 Isuzu i-290/i-370 (TI)
2006 Isuzu i-280/i-350 (TI)
Service Information
The purpose of this bulletin is to explain when the front safety belts are supposed to lock. There are several different locking situations.
Vehicle Sensing
This type of locking occurs in response to the vehicle under the following conditions:
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The vehicle changes speed or direction abruptly (the vehicle goes into high acceleration OR high deceleration).
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It can also occur in a static condition when a vehicle is parked on a large slant (fore-aft or side-to-side) such as streets in San Francisco California.
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It may also occur over rough road conditions where the retractor mechanism is bounced into a locked condition.
In all of these conditions as long as tension is maintained on the webbing the belt will stay locked. When the tension is released the belt retracts slightly
the lock bar disengages and the safety belt should return to normal function. Please inform customers that may comment that "the belt locks
intermittently" that this is the design intent and the belt is functioning properly.
Web Sensing
This type of locking occurs in response to the extraction of webbing. When the webbing reels out at an accelerated rate it goes into lock mode and stays
there until tension is again released. To observe this condition extract the webbing quickly. Customers may refer to this condition as "intermittent
lock-up" and encounter it when trying to put the belt on too quickly.
Automatic Locking (ALR)
This type of locking is provided at the right front passenger position of most vehicles. When the webbing is pulled all the way out it automatically
converts the retractor into a cinch-down mode (i.e. ALR). This is typically used to tightly secure a child seat to the vehicle. Some customers may
experience inadvertent activation of ALR mode if they happen to pull the belt all the way out to the end of travel while they are putting the belt on. The
ALR mode of operation is automatically cancelled when the belt is unfastened and stowed (the belt returns to normal sensitive function).
Overspool Lock
There is an unintentional locking condition that ALL safety belts from ALL manufacturers may experience called "overspool lock". If the webbing snaps
back to the stowed position rapidly enough the retractor will lock with the belt fully stowed. This is more likely to occur when customers "help" the belt
to retract. Without the weight of the latch plate and friction to slow the retractive speed of the webbing the higher than normal webbing retraction speed
that occurs engages the locking mechanism when a sudden stop occurs at the end of web travel. Since the webbing is now fully loaded on the spool the
retractor cannot rewind itself further to release the locking mechanism. When this happens the belt cannot be pulled out to wear. When customers bring
their vehicle to the dealership with this condition they believe replacement is necessary. Replacement is not necessary for this condition. All the Service
Advisor needs to do is pull hard on the locked webbing and then release. The hard pull extracts a small amount of webbing from the retractor which in
turn permits a small amount of retraction to occur when released. This is all that is needed to disengage the locking mechanism. The safety belt will now
function properly.
Disclaimer