Passenger cabin seat belt issue

[K120]

I have a 1999 Expedition XLT. Most of my passenger cabin seat belts won't engage the belt lock when I pull suddenly on them. I'm concerned that they won't lock up in the event of an accident/sudden stop.

Has anyone here had this issue, and if so is there any kind of DIY fix for it or do I need to find some replacement seat belts? The driver and front passenger belts lock immediately with just a short tug.

Thanks.

 

[jr1under]

According to my 1999 Owner's Manual, there are two types of locking modes: vehicle sensitive and automatic. Vehicle sensitive is the default and locks in response to vehicle movement like a sudden braking or impact.

My second row outboard belts won't lock just by yanking on them unless I buckle the belt, pull it out as far as it will go and let it retract. I guess that is automatic mode.

 

[K120]

I was under the impression that "vehicle sensitive" locking was true of all retracting seat belts, whereas "automatic" locking was a secondary (but less common) feature. I find it hard to believe that the second row belts are only supposed to have the "automatic" (pull out to lock) mode. Surely you'd want every single passenger seat belt to lock when there's an accident?

Out of curiosity, do your third row outboard belts lock when pulled on? If they do, then why don't the second row belts?

 

[jr1under]

I find it hard to believe that the second row belts are only supposed to have the "automatic" (pull out to lock) mode. Surely you'd want every single passenger seat belt to lock when there's an accident?

I think maybe the words got in the way of the meaning here, mine and Ford's. The second and third row outboard seats have both modes as does the front passenger seat.

Automatic(I would have called it 'fixed') mode locks the shoulder belt at whatever length it is when buckled and there's no give. It's restrictive for a normal passenger but what you'd use to secure a child seat, package, etc.

Vehicle sensitive is the default mode. The shoulder belt allows freedom for the normal movements made in a car but the belt locks upon abnormal events such as hard braking, sharp turning or 5+mph impact. I don't know how to verify that it's operational but yanking on the belt is not a valid test.

 

[K120]

Okay that's what I thought, but I'm still puzzled why 3 out of 4 rear passenger belts don't lock when I yank on them. The front two do, and at least one of the third row belts does. Why is that not a valid test, given that it works for some of them? I'm very concerned that the belts won't lock in an accident. How else can you test them?

 

[jr1under]

Mea culpa.

I searched online for an explanation of why the yank test isn't useful and instead found the opposite - it is indeed a valid test. Some sites call it a sudden jerk test which also describes how I feel about disputing it.

Thanks to your persistence, I'm now checking into possible problems with my own second row belts.

 

[K120]

No problem. Please let me know if you find anything!

 

[jr1under]

No problem. Please let me know if you find anything!

I did find that yanking on the belt is a test of the Emergency Locking Retractor - if the belt doesn't lock, the ELR is probably bad. A lot of plastic trim has to be unsnapped just to get to the mechanism and that's as far as I got before bailing.

 

[K120]

Where did you see that yanking on the belt is a genuine test of the ELR? I've always assumed that's the case (especially since my front belts do what I expect i.e. lock immediately) but I recently read another forum thread that seems to indicate that's not necessarily the case (see here - it's for an 80s Ford Ranger, not a 99 Expedition, but I assume the principle (if correct) might still apply).

 

[jr1under]

Until this thread, I'd assumed it wasn't a legit test but some fact-checking proved me wrong. Here's a couple of links:

You can also Google "testing seat belt by jerking" to check out other results plus the AI Overview.

How To Check If My Seat Belt Will Work In An Accident?

How To Check If My Seat Belt Will Work In An Accident?

www.team-bhp.com

How To Test a Seat Belt: Step-by-Step Guide

Learn how to test your seat belt with this step-by-step guide. Spot issues early and rely on MyAirbags for fast, certified repairs that restore safety.

blog.myairbags.com

 

[K120]

Apparently the issue might be that the rear belts lock via a "vehicle-sensitive" inertia-based mechanism, and thus jerking on them doesn't engage the lock. I read you may be able to test this by parking nose-down on a steep slope, or by slamming the brakes or going over a speed bump rapidly. The front belts presumably have a so-called "belt-sensitive" locking mechanism which will lock when the belt is yanked on regardless of the vehicle movement/orientation.

Here's an example link: https://saferide4kids.com/helpie_faq/when-i-tugged-the-seat-belt-it-didnt-lock-is-it-working/

I'm still looking into it.

 

[jr1under]

Well, I certainly know more about seat belts than before this thread started but there's still some uncertainty.

The 1999 Owner's Manual states that vehicle-sensitive is the normal mode for lap/shoulder belts. There's no mention of belt-sensitive yet both front belts lock when yanked. Does this mean the front is both vehicle- and belt-sensitive?

You mentioned that one of your four rear outboard belts did lock when you yanked it. None of mine do. Wonder what's up with that outlier?

 

[K120]

I need to test it again, it might have been a mistake on my part. Or the car was on a slope, or I pulled it out too much (engaging the ALR) or something.

I think the front belts are both vehicle- and belt-sensitive. Or possibly belt-sensitive is superior (i.e. more reliable, or quicker to respond) and so the front belts only have the belt-sensitive locking mechanism.

If the manual itself says the rear belts are vehicle-sensitive then that probably answers the question. I do wish there was a way to test it easily (i.e. without slamming the brakes with someone strapped in) though.