1993 SL2 Automated shoulder belt dashboard light stays on

I have a 1993 SC2 with a manual transmission: This pertains to the driver side belt. These cars came with the automatic shoulder belts that open and close in sync with the status of the door. There is a light (shoulder belt icon) on the dash indicator bar that turns off when the shoulder belt is secured, as well as another light ("lab belt") that does the same when the waist belt is secured. The waist belt light works fine. I replaced the whole shoulder belt track and motor assembly this past November after the previous assembly had jammed partially open. After installing the replacement system the dash light worked correctly, however, as the winter months went on, sometimes while driving it would stay off, and other times it would stay illuminated, despite the belt being secured in the right place. Other times the light would turn on and off, irregularly, within the same drive. It is now stuck in the on position; the shoulder belt icon light is now always on whether the belt slider is parked in the open or closed position. The chime sound and glowing light on the dash while the belt is correctly stowed has gotten annoying. I am trying to correct the problem and silence both.

A few days ago, I took apart the control module under the parking brake/console and cleaned the contacts for the respective connectors, especially those for the automatic belts system. They were not corroded, but I cleaned them anyway. I also checked the seating of the two connectors that plug in at the seat belt motor. One connector comes from the slider end position switches of the two latch/parking mechanisms built into each end of the rail, and the other provides power to the motor from the battery. I took apart the closed-position latch for the slider and reassembled it. This seemed to have solved the problem, restoring the on/off function of the light, but only for the moment that I tested it with the interior all taken apart. After reattaching the rear seat and all of the interior panels and sealing everything back up, the light remained on again.

Does anyone understand the dash light feedback system for these shoulder belts? Where is the signal made that tells the dash light to illuminate or turn off. As far as I have learned, there are two position switches (very small tabs) that tell the system to stop the motor when the slider reaches the end of travel for both the open and closed positions. Is there an electrical loop within these that is synchronized with the closed position end that, upon contact/no contact, triggers the light? I suspect there is a lack of contact for the closed position somewhere. Is there a contact point or suspect component on these? Am I missing something?

Thank you all for your help.

 

Thank you for the link. There is a lot tied into this system, and it will be difficult to test every associated wire.

I took the seatbelt rail system apart and tested the switches at both (open/closed) positions, as well as the continuity of the circuits up to, and through, the junctions at the retractor motor. The switches do their job, the motor works, and those circuits seem to be working fine. The light stays on.

I think I will have to dive deep and take out the driver's seat and area carpeting to access the lines that run from the motor unit junctions to the PRCM box under the console. I suspect that there might be a faulty circuit in that section of wiring.

 

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It is not too terrible to remove the center console to access the control module. I did that, inspected, and cleaned everything up on the module/terminals. Thankfully, no drinks have been spilled on this one. I imagine that that somewhat precarious location is why such a robust case surrounds the PRCM circuit board. The terminals are still vulnerable, though, but not much corrosion was on mine.

I could take it all apart again and see if the wires running from the module to under the seat and out to the motor are in proper condition. At this point, I am unsure of the nature of the wiring routing from the door sill motor location to the control module under the console. Is there a ground location under the carpet that serves various wires? There has been some water in the driver footwell a long time ago from when the sunroof drains were plugged up and some prolonged rain overwhelmed them: flooded carpets. I wonder if there is wiring/ground damage somewhere in this unknown-to-me under carpet area that recently worsened to the point of failure. Just thinking out loud.

I imagine that there are not many of these cars on the road with the belt track system, let alone a working one. My car is ancient by current standards; I can see how my asking this question now is a bit surprising for you.

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I like your idea of taking apart a seatbelt buckle and learning its components. Interesting that you mention the possibility of an in-buckle switch there. The lap belt works correctly--no dash light issues there--but the shoulder belt . . . I don't see any wires that are attached to the mouse belt slider male end. The shoulder belt buckle (female) has no wires, either, but maybe there is still a magnetic switch within that buckle that eludes my understanding. How would such an in-buckle signal transmit? The only wired switches for the shoulder belt that I am aware of are the A and B position proximity ones that the motor seems to use when the belt is in either position. It would be interesting if there is indeed a magnetic handshake in the shoulder buckle that controls the telltale light on the dash.

Looks like I will be going to the salvage yard as soon as I can to take some shoulder belt buckles apart. Do you know if the plastic casing on the buckle is glued, or does it use slot/tabs to encase the mechanism? I've never opened one up and want to know if I'll need to bring something extra to cut open a glued/welded plastic buckle without destroying it. I will investigate the shoulder belt buckle situation before tampering with any carpeting in my car.

Thanks again for your help. Were you on the Saturnfans forum before the site went down? I feel very lucky that this one exists for help. I bet my question had already been answered in that massive repository of knowledge for these cars.

 

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I went to the salvage yard and got the shoulder buckles from the driver and passenger seats from an SL2 of the same year as mine. [That car was in immaculate condition; someone already took the whole front end/drivetrain, including front axles and knuckles, as well as the instrument cluster and driver's seat. The OEM exhaust system was still silver in color, as was the shielding. Car must've never been driven. Rear calipers and knuckles still silver colored. . . zero rust on anything. Wishing there were more parts left to take on that thing.]

The shoulder buckle designs are identical to those in my car, and the passenger and driver side buckles are also the same. I opened the plastic shell (pried at the seams) and was able to look inside. Looks purely mechanical on these cars, as far as buckle to slider connection is concerned. The internals of the mechanism are composed of a compact, yet robust, metal housing coated in plastic that has two springs to actuate the lock/release of the buckle via the orange button on the exterior. The entire housing is about 1.5" x 2". There is no room inside the housing for any sensing switches, reed type, or otherwise. Strictly, there is a slot for the mail end within the metal housing and the springs to actuate the release/hold mechanism. No wiring or unaccounted for space within the housing or on the mouse slider (as mentioned in a previous post).

I suspect that the mouse belts are somewhat of a nonspecific system, where the actual connection of the shoulder belt buckle to the slider isn't important, but rather the position of the slider itself being the case. I imagine that the A vs B position of the mouse signals via the microswitches to the SRCM under the console whether the light should come on or not. I tried both of the buckles I got from the yard and neither made any difference at the dash when the belt was in the closed, "B" position.

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Everyone knows that anything found on the internet is correct. Always.

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The mechanical switch described in your findings is indeed present in the lap belt buckle, but absent on the separate shoulder belt one. There is a wire that feeds from that lap belt buckle into the console, presumably to the SRCM. Somebody also took the driver seat from that car I mentioned above, including the lap belt switch mechanism. I wanted to investigate that while I was in there, but someone beat me to it. The passenger seat lap belt does not indicate open/closed with a dash light for these cars, so there is no switch or wiring for that one. I suspect the lap belts use the same type of microswitch as found in the mouse track system (A and B positions) and the closed position on the sunroof rail. (I recently rebuilt my broken sunroof rail componentry, and saw the same type of microswitch as found on the SRS track positions.)

Yeah, most of the switches on these cars seem to be electromechanical. No Hall effect switches on the belts. I took apart a microswitch (from a donor car closed "B" mouse belt track position) and there was a simple spring actuated open/close gate that closes/opens the circuit with the slightest touch from the little tab on the exterior of the microswitch.

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I find this interesting: the switches themselves are good, as I tested them for continuity, and the motor knows to shut off when the belt reaches position A and B. There is only one wire coming from position A and one from B going into the wiring junction at the motor. Several wires, of different color than those of the A and B switches, exit the seatbelt motor junction area and feed into the harness under the doorsill. I wonder if some of the A vs B position, open/closed, signal is used by the PRCM to light the dash or not. If so, maybe there is a fault along the way from the motor junction to the PRCM. I think I may have to check the condition of the wires running under the doorsill, seat, and carpet.