T680 Seatbelt Locking Up

Topic 33660 | Page 1

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Pothole's Comment
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This is the 3rd or 4th time it’s happened in about 6 months.

This morning I sat down in the driver’s seat and the seatbelt was locked up.

The spool inside the plastic body panel from which pays out or winds the slack in the belt is stuck. Also, since the seatbelt is attached to the seat it won’t go up or down either.

The first time or two the spool would eventually release itself and I’d be able to pull the belt out and attach to the latch as normal.

However the last time this happened about a month ago it wouldn’t release after a day so I stopped at a KW dealership and two of the service writers managed to get it released. One guy lifted the seat to take some tension off the belt and the other guy kept yanking on the belt until it finally released.

That time it happened I had dropped my trailer at a customer site. The next morning when I left the truck stop the seat belt was locked up. I went about a mile and lost secondary air pressure. I pulled over on the shoulder ant let my pressure build then went and hooked up to the trailer.

About a week ago I had the terminal mechanic service the truck. He told me that he swapped the pressure sensor. I made a 3000 mile round trip and got back to the yard yesterday.

I bobtailed around the terminal yesterday. I lost pressure but it built right back as before. Told the mechanic and he said the truck would need to go to the dealer at some point. So I hooked up to a trailer and picked up a load.

After getting loaded I shut down on the shoulder in front of the customer site. This morning the seatbelt was locked up.

When I lose my secondary air pressure it drops from around 125 to 50 in about 1-2 seconds and the transmission won’t shift. Less than a minute later the pressure climbs back to 125 in about 1-2 seconds. However I don’t think I’m actually losing pressure in my tanks because I don’t hear any air bleed off. If I was really losing pressure that quickly there should be a loud blow off. But there isn’t one.

Since the seat is air ride I’m thinking the two may be related.

Any ideas what’s causing this?


"Bobtailing" means you are driving a tractor without a trailer attached.


A facility where trucking companies operate out of, or their "home base" if you will. A lot of major companies have multiple terminals around the country which usually consist of the main office building, a drop lot for trailers, and sometimes a repair shop and wash facilities.

Grinch's Comment
member avatar

The seatbelt spool locking and the pressure drop are two different un related items.. I run a 2020 t680 myself.

The air pressure drop is simple. The air pressure regulator cutoff switch needs to be adjusted down. What is happening is it is charging up hitting 150. And it temporarily overpressurizes the gauge, that make your needles drop down. Then next shift it bleeds enough pressure to read correctly. This is a common t680 issue.

The seatbelt is mechanical only. No air. It sounds like mine passenger one. Same issues replaced the seatbelt and spool and no more issues. Sometimes you just get a bad one.

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