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Volvo 850 Seatbelt Jamming

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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Volvo 850 Seatbelt Jamming

Post by Cookeh » Fri Aug 23, 2019 8:03 am

Good morning,

Yesterday my 850s drivers side seatbelt completely jammed on me, wouldn't retract or extend. After some Googling I found quite a lot of links to here and other forums, where it appears to be a somewhat common problem, with no real fix other than replacing it. I had a need to get to work this morning, so I had to try and fix it, and it seems that I managed just that - so I will document the process here in the hope that it helps someone else in the future.

Any comments or questions, please ask and I am also happy to make edits to what follows to make it clearer or easier to follow. Pictures aren't great as daylight was failing and I was in somewhat of a rush.

Here is the problem I was facing, wherein my seatbelt was completely jammed and would neither release nor retract.

1) Using a 10mm socket/wrench undo the negative battery terminal and remove it. Insert your key into the ignition and move it to position III to drain the remaining power from all the relays. This is important to avoid any SRS lights/errors.

2) Moving inside the car, we need to remove the trim piece at the side of the seat, which is done by lifting it up to 40 degrees or so and then pushing it towards the back of the car. I would then always put the safety block into the airbag trigger (if you have mechanical triggers).

ImageTrim panel removed

3) Next, undo the 12mm bolt that is holding the seatbelt to the seat rail. At this point, it might be useful to use something to stop the seatbelt from further retracting. I used mole grips, but needle-nosed mole grips would be better.

ImageLower belt mount

4) Remove the B-pillar trim. I find this easiest to remove when I pull from the top and make my way down. There are no bolts, just clips. Take care at the bottom as it is held under tension to the sill/door trim pieces which are decidedly more fragile. This exposes the seatbelt mechanism:

ImageSeatbelt assembly

5) Unclip (just pull straight outwards) the SRS cable

ImageSRS cable unplugged

6) Undo the two 14mm bolts (one of which is visible just above the SRS clip, the other is at the top of the seatbelt assembly) and the single T30 screw securing the P-clip on the cylinder at the base of the mechanism (visible with a red head in the above picture). This will now free the assembly completely and you can remove it. Mine was very tangled, which may have contributed to the issue, and certainly was causing it to retract more slowly and with more resistance than it should have.

ImageSeatbelt tangled

7) I took the time to untangle my seatbelt and re-route it correctly. In the bottom of this picture you can see thick butyl tape just beneath the reel. Beneath this is a clip and two push-rivets, which contains the cogs and the seatbelt gyroscope.

ImageRewound seatbelt

8) With this lower panel removed or simply lowered for access, you can clearly see the mechanics of the seatbelt.

ImageWind and lock mechanism

Not pictured is the 'gyroscope' that controls when the seatbelt locks. It is shown in the following video, also demonstrating how it works:

Now that we can see the components, we can try and understand how the seatbelt works and what is causing the jamming. In the video, we can see a little arm that sticks out from the assembly. That arm sits in the 'D'-shaped green loop pictured above.

When the seatbelt is in its normal position, this arm sits flat and pulls the 'D' away from the cog. This is the main part that allows it to spin and move freely. When the seatbelt is in any other position (such as when the car is on an angle/rolled/inverted/etc), this arm is pushed away from the assembly, pushing the 'D' into the cog which locks its position.

In addition to the two green components (the 'gyroscope' and the 'D') you can also make out a small metal piece, almost triangular in shape, just in front of the plastic 'D'. This, from what I experienced, affects release/extension of the seatbelt but not it's retraction or locking. When in the position pictured, it rests against the pin on the bottom of the 'D' and allows movement. When behind (from the POV of the picture) the pin on the bottom of the 'D', the seatbelt can be retracted but will not extend.

Hopefully that all makes sense, and hopefully with that knowledge we can now try and fix the seatbelt.

9) Using a pick or small thin object, ensure that the 'D' is pulled away from the cog, and the metal triangular pin is in front of (from POV as pictured) the 'D'. This should then enable you to fully extend the seatbelt and let it retract slowly, ensuring it doesn't foul anywhere on the cartridge. It should look as pictured, with the addition on the gyroscope on the RHS.

ImageWind and lock mechanism

10) The next step is reassembly. Closing up the bottom plastic piece and bolting the mechanism back onto the B-pillar. I would recommend, however, taking an additional step first. Use some thin string/fishing line/dental floss/similar to tie a loop around the 'D' and feed it out before you close it the area up and remount the belt. After approximately 4 attempts of making sure the 'D' was pulled away and everything was working okay, I found that the second I tilted it to mount it and got it bolted up it would jam again. By tying the string around it I was able to mount it, and then release the 'D' so I could extend and then retract the belt once more.

By doing these steps, and ensuring there was something attached to the 'D' to pull to release it after mounting I now seem to have a fully functioning seatbelt again. I have just tucked the line behind the B-pillar trim so it is out of the way, should I need it again.

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Re: Volvo 850 Seatbelt Jamming

Post by Kara503 » Fri Aug 23, 2019 5:59 pm

Thanks for posting!!!! I had this problem not too long ago on my 855 and just opted to replace the whole assembly with one I found at a yard. I'll try your process on the old one that is still jammed, I kept it :)

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