Seat belt won't tighten - MY MISTAKE

[Paul]

Evening all,

Despite owning it for quite some time I've only just found that the front passenger seatbelt in my CROWN Vic never goes taut. I can yank on it from all angles and it never goes tense. All the others are remarkably sensitive and easy to catch.

My son has to sit up front now (he needs a 3 point seatbelt for his car seat) and I'm not keen on him flying forward because of a faulty seatbelt - is it possible to service or repair the tensioner? I can get spares from the US but they ain't cheap...

[mk2cossie]

Does it lock if you are actually braking?

As not all seatbelts will lock if you give them a quick tug whilst pulling on them

It may even just need the mechanism blowing out of accumulated dust and fluff too

[comfortablynumb]

Does it need to be OE, or would a generic belt do, even as a temporary repair?
My grandsons seat is fitted in the centre of my rear seat with a lapbelt, I've found that by putting my knee in the seat, I can pull the belt tighter and stop any movement, and then of course he's held in by the straps in the seat

[LowStandards]

Do you mean it doesn't return?


Pull it all the way out and clean the belt, then spray it with furniture polish

[droopsnoot]

It might be less costly to have it refurbished in the UK than to source one from the US, even though that doesn't sound likely. I've had seatbelts done by Quickfit SBS and FDTS with very good results - though the main reason I went to FDTS for the second set was because Quickfit weren't replying to emails, one of my pet hates. May be different now though.

[Paul]

Feb 18, 2022 8:11:01 GMT LowStandards said:

Do you mean it doesn't return?


Pull it all the way out and clean the belt, then spray it with furniture polish

It returns fine... It just doesn't seem to lock when you yank on it.

Great tip on slow returning seatbelts though!

[slater]

It's a simpme mechanism that may well have just seized up. Clean and lube may well fix it.

[jimi]

Feb 17, 2022 20:44:57 GMT mk2cossie said:

Does it lock if you are actually braking?

As not all seatbelts will lock if you give them a quick tug whilst pulling on them

^^^^^^^^
This, they have an internal inertia locking mechanism that only locks under braking ( a sort of pendulum latch) IIRC correctly it used to be mentioned in the MOT manual that that it couldn't be checked for technical reasons.

[Paul]

Feb 23, 2022 1:41:39 GMT jimi said:

Feb 17, 2022 20:44:57 GMT mk2cossie said:

Does it lock if you are actually braking?

As not all seatbelts will lock if you give them a quick tug whilst pulling on them

^^^^^^^^
This, they have an internal inertia locking mechanism that only locks under braking ( a sort of pendulum latch) IIRC correctly it used to be mentioned in the MOT manual that that it couldn't be checked for technical reasons.

Quick update - I've taken the whole mechanism off the car (4 screws, 3 bolts - a doddle).

Strangely when unbolted from the car it works absolutely fine - it's sensitive too tugs in any and all directions and locks as it should.

So I blasted it with compressed air and a tiny spritz of WD40 on the wheels.

Refitted and exactly the same problem ☹️. It must be the exact angle of the webbing being pulled out.

It's not possible to inspect the mechanism as it is - it's protected by a plastic shroud. Definitely looks like a pendulum-type mechanism in there. However it's only held in place with one rivet.

Looks like I'll have to snap that off to get a closer look as it's trying to to do its job.

[jimi]

I think your seeing a problem where there isn't one, they are meant to lock under braking not when stationary. The only way I can think of to test it properly would be to pull it under braking which is not really practical. Even the MOT doesn't check that part of seatbelt operation mattersoftesting.blog.gov.uk/urban-myths-of-the-mot-test/

[misterm]

Inertia belts are quite sensitive to the position they are fitted in. Does it have some sort of locating peg to make sure it is only fitted in one position? This is why the generic ones have adjusters so that when fitted the setting can be suited to the angle the reel is fitted at.

[jimi]

Found an interesting video on seat belt design & operation Learned a few things from it

[Paul]

Feb 23, 2022 10:41:02 GMT jimi said:

I think your seeing a problem where there isn't one, they are meant to lock under braking not when stationary. The only way I can think of to test it properly would be to pull it under braking which is not really practical. Even the MOT doesn't check that part of seatbelt operation mattersoftesting.blog.gov.uk/urban-myths-of-the-mot-test/

I hear you, but all other 4 inertia reels (including the driver's which is identical but flipped) lock as they should when pulled. They pretty sensitive.

It's not an MOT issue - it's to do with getting a car seat in the front. Now that he's older my boy needs a bigger booster and that requires a 3 point belt to secure...the ones in the back are only 2 point.

[jimi]

I learned from the video I linked to that there are basically 3 types one will not lock by pulling, one will lock if pull it quickly enough ( it has two separate mechanisms) and the third will lock on a quick pull but will release slightly under enough load.
I didn't know about types 2 & 3 so my previous comment isn't really valid, apologies. Sounds like you may have have type 2, have you tried pulling it really quickly?

[Paul]

Feb 23, 2022 10:41:02 GMT jimi said:

I think your seeing a problem where there isn't one, they are meant to lock under braking not when stationary. The only way I can think of to test it properly would be to pull it under braking which is not really practical. Even the MOT doesn't check that part of seatbelt operation mattersoftesting.blog.gov.uk/urban-myths-of-the-mot-test/

Well I owe you an apology - you were quite right, I was wrong. Because my wife (who only has experience of newer cars) was quite insistent there was a problem, I went looking for a problem.

Here's the seatbelt removed from the car



One little rivet (already removed by me) holding the cover on



Pendulum design




So of course the reason it was latching in every position but the fitted one was because it is working as designed...any jolting off centre was using gravity to lock the seatbelt.



I needed the comic sans font version to understand it.

Well, mechanism cleaned up, refitted and headache sorted.

[jimi]

No apology necessary, without removing the cover there was no way of being sure and you want to be sure when it comes to seat belts.
Good to see the pictures and the diagrams, all stored away in the back of my memory for future reference