Man… Talk about unpredictable and defying all conventional logic and reasoning!!!
I reasoned that if there were a break in any one of the wires, it would have occurred where the wires experience the most flexure. In my case that would have been somewhere after the wires disappear into the hole of the seat cushion. Just by pressing down on the seat bottom, I could see that that was the only place where any visible movement or flexure was occurring. Elsewhere, the wires were tied down and would essentially remain unmoving when anyone adjusted the seat or sat down on it.
I almost gave up right there, because I didn’t want to remove the leather seat cover entirely to get at the wires near the sensor itself. Nevertheless (against my logical intuition), I decided to test the continuity of the wires anyway, because of the experiences reported by others in this thread. Outside of the cushion, the three wires are encased in a black molded-on sheath. I carefully cut open this sheath, as near to the bottom of the cushion as I could get, and tested continuity of each wire between there and the yellow receptacle (don’t call it a plug). I simply clamped a sharp needle into some locking forceps, attached my tester to that, and poked each wire. It took almost no pressure to penetrate the thin insulation on each wire with the needle and make contact.
Damned if I didn’t find a break in the white wire! Then it became a matter of locating the break. Again, I made small cuts in the black sheathing and tested the exposed wires with the needle, using logic to guess where the break might be. I ended up making radial cuts at 6 different places along the length of the sheathing before I narrowed it down, because the break in the white wire wasn’t anywhere near a tie, a sharp bend, or anywhere else where you might have guessed it would be. I am thinking now that the break occurred, not because of normal movement of the seat, but simply because of small vibrations. I think the manufacturer used a bad batch of wire, where at some places the copper strands were mostly already broken and just barely hanging together by a thread to begin with, or that wires got pinched during the assembly process.
So, let this be a lesson. Set aside all logic and reasoning and just go by the experiences of others and myself in this thread. This has to be one of the weirdest problems I have ever encountered. I don’t think MB can be blamed for using solid-core wire. In fact, the conductors inside my white wire were clearly multi-strand. But I do think MB can be blamed for not investigating why so many sensors fail and for shoddy quality control, particularly because this problem seems to transcend many different models and years. A simple stress test would reveal when a bad batch of wire comes in to the manufacturing facility. Nowadays, there are also electronic tests that can detect and pinpoint where faults or weaknesses occur along long lengths of insulated wire in bulk shipments. And a simple review of assembly procedures would reveal if handling there were causing the breaks.
My white wire clearly showed telltale signs of having been pinched and nearly severed before it was encased in the black sheath. I think I was just plain lucky that it was in an accessible place. Sure, it still took several hours to find and repair it, but it saved me hundreds. Kudos to this forum.
I reasoned that if there were a break in any one of the wires, it would have occurred where the wires experience the most flexure. In my case that would have been somewhere after the wires disappear into the hole of the seat cushion. Just by pressing down on the seat bottom, I could see that that was the only place where any visible movement or flexure was occurring. Elsewhere, the wires were tied down and would essentially remain unmoving when anyone adjusted the seat or sat down on it.
I almost gave up right there, because I didn’t want to remove the leather seat cover entirely to get at the wires near the sensor itself. Nevertheless (against my logical intuition), I decided to test the continuity of the wires anyway, because of the experiences reported by others in this thread. Outside of the cushion, the three wires are encased in a black molded-on sheath. I carefully cut open this sheath, as near to the bottom of the cushion as I could get, and tested continuity of each wire between there and the yellow receptacle (don’t call it a plug). I simply clamped a sharp needle into some locking forceps, attached my tester to that, and poked each wire. It took almost no pressure to penetrate the thin insulation on each wire with the needle and make contact.
Damned if I didn’t find a break in the white wire! Then it became a matter of locating the break. Again, I made small cuts in the black sheathing and tested the exposed wires with the needle, using logic to guess where the break might be. I ended up making radial cuts at 6 different places along the length of the sheathing before I narrowed it down, because the break in the white wire wasn’t anywhere near a tie, a sharp bend, or anywhere else where you might have guessed it would be. I am thinking now that the break occurred, not because of normal movement of the seat, but simply because of small vibrations. I think the manufacturer used a bad batch of wire, where at some places the copper strands were mostly already broken and just barely hanging together by a thread to begin with, or that wires got pinched during the assembly process.
So, let this be a lesson. Set aside all logic and reasoning and just go by the experiences of others and myself in this thread. This has to be one of the weirdest problems I have ever encountered. I don’t think MB can be blamed for using solid-core wire. In fact, the conductors inside my white wire were clearly multi-strand. But I do think MB can be blamed for not investigating why so many sensors fail and for shoddy quality control, particularly because this problem seems to transcend many different models and years. A simple stress test would reveal when a bad batch of wire comes in to the manufacturing facility. Nowadays, there are also electronic tests that can detect and pinpoint where faults or weaknesses occur along long lengths of insulated wire in bulk shipments. And a simple review of assembly procedures would reveal if handling there were causing the breaks.
My white wire clearly showed telltale signs of having been pinched and nearly severed before it was encased in the black sheath. I think I was just plain lucky that it was in an accessible place. Sure, it still took several hours to find and repair it, but it saved me hundreds. Kudos to this forum.
