Converting a Sprinter 3-passenger Seat to a 2-passenger
I kept one of the 3-passenger seats that came with my passenger van so that I could carry extra passengers in the second row. Unfortunately, I had to remove the galley cabinet whenever I wanted to install the seat. I knew my ideal setup would be to have a two-passenger seat that I could install without having to remove the galley cabinet. I didn’t have any luck locating a double seat that would fit in the factory rails, but I did run across a forum post that described the process of converting an existing factory seat. With this inspiration, I embarked on the conversion.
Disassembling the Factory Seat
The first step was to remove the seat belts and associated fixtures so I could remove the seat cover. After removing the seat belts and fittings, I began removing the seat covers. This mostly involved un-clipping a series of connectors that attach the fabric to the seat frames and cushions.
The seat belt covers are held in place by a small screw that is hidden under belt inside the cover.
Inside the shoulder belt cover is a plastic piece (which serves as a handhold) that can be pressed out after the cover is removed. Once the covers are removed, the seat belts and receivers can be unbolted from the seat.
The seat covers are held in place by a variety of clips that can be easily located and detached.
The fabric around the seat belt attachments is clipped to wires that are embedded in the foam.
A wider angle looking at the wire that holds the seat cover in place at the seat belts.
The seat release mechanism has cables that are simply zip-tied to the frame and springs. I cut these ties.
Here the seat cover is pulled back showing the seat belt inserts. The covers are also attached at “tuck-clips” embedded in the foam at the seams of the seat. These clips are stout but can be released by pulling on the cover. You can also work as small screwdriver into each clip to make it a bit easier.
This seat also had a plastic back-panel under the fabric that simply held on with screws. The back cover had zippers on the sides – obviously making the removal much easier!
This is looking from below at headrest brackets. These plastic inserts can be removed by pressing on the plastic tabs that hold them in place along the sides. This was made much easier by removing the rear plastic panel and pulling up as much of the back of seat cover as possible.
The last part of the dis-assembly was removing the seat cushions. I don’t have any photos of this because it involved simply pulling the foam off the frame.
Modifying the Seat Frame
This was the critical part of the 3 to 2 modification. In general, this involved measuring and marking the section to be cut out, cutting out the middle of the frame, fitting the frame ends back together, and welding the frame together.
I took great care in measuring the section that needed to be removed. The resulting spacing between the seat supports needed to be 18 1/4″ to match the factory rails. There is some leeway here, but not much, maybe a 1/8″ either way. It seemed to me the key to getting a good fit was to cut as precise as possible then fit the seat into place before doing the final welds. I made my cuts away from the supports (about 2″) to give me more room for the welding and fitting. In theory, the section to be removed was same width as the spacing between the supports (since one support is being removed) which was 18 1/4″ between cuts. Nevertheless, I left one side a bit long understanding I would need to do a second cut. After I got into it, this proved to be unnecessary caution.
I used the straight edge of a piece of paper wrapped around the tubes to mark a straight cut-line. My reciprocating saw fitted with a metal cutting blade cut the tubes quickly and cleanly.
One set of cuts done. Note that these were a bit long on purpose. I cut the upholstery attachment rods and brackets closer to the support frame making sure to leave enough to weld them back in place. The bracket holding the release mechanism was mounted on the middle section, so I cut this off to use later on the modified frame. I also had to remove the back springs since they ran horizontally and attached to the middle section.
During the cutting process I found that in the front of the seat frame, there’s a smaller diameter extension pipe that is fitted into the main pipe. This inner pipe is welded in place, but extends a good distance inside the main tube and past my cut line.
After carefully cutting through the just the outside tube, I was left with a section of inner tube that extended out about 3″.
I liked the idea of using inner sleeves (tubes) to hold the frame together. This method would make the sizing of the seat width and the welding much easier. It would also add considerable strength to the assembly – especially with the smaller gauge tubes.
The initial fitting and measuring to check if I was in the ballpark. Note the release mechanism on the floor. I didn’t need to take the cabling off, just move it out of the way as I was cutting and welding.
Though I did a fair bit of searching, I had a hard time finding stock tubing that would fit snugly into the factory tubes. I ended up cutting 4″ sections of the factory tubes from the scrapped middle section. I cut a lengthwise slot in each of these using my angle grinder. By gently hammering each section closed again, I effectively created a smaller diameter pipe. Of course, the width of this lengthwise cut (and corresponding decrease in circumference) was dependent on the diameter of each tube. I could have done the math on this, but ended up just estimating the width and gradually decreasing the diameter in small increments. Although this sounds complex, the process only took about 30 minutes to fabricate all the sleeves I needed.
A nice feature of these custom sleeves was that I could make them fit pretty tight (I had to tap them into place) which held the seat frame together for a final sizing to the rails. I also found that by using these sleeves, I could make my final cuts in the seat frame a bit wider than necessary to allow some leeway for adjustment and sizing.
I had a buddy come over and weld the joints as well as the small metal rails for the seat cushion and upholstery attachments. (I finally bought a welder after this, so hopefully in the future I’ll be doing the welding part myself).
Here’s the frame tack-welded together. The bracket for the release mechanism still needed to be welded on.
After welding, I rechecked the fit in the van and it fit perfectly. Honestly, cutting-sizing-welding was the part that intimidated me the most and kept me from doing this mod for almost a year. As it turns out, it wasn’t that difficult to get the sizing correct.
Cutting the Seat Cushions.
The sizing of the cuts for the seat cushions was pretty straightforward: I simply measured and marked the center of the hump between each seating space and cut out the middle seat section. Before cutting I verified that the remaining sections would fit the same cutouts and attachments and thanks to the symmetry of the factory seat design, everything was in place. In my seat, there was a wire attachment fixture that’s embedded in the foam. I cut these wires with a hacksaw where they crossed the cut line. These wires aren’t structural so I wasn’t worried about trying to retain the full fitting (and it wasn’t a problem). I cut the cushions using my ever-handy foam cutter (an electric carving knife), which is really the absolute best way to cut foam.
I assembled the cushions back together using adhesive spray rated for foam. It took a couple coats of glue but it worked quite well. I could have cut the cushions in a less obtrusive location, but I wanted to use the thickest part of the foam to get a larger surface to glue.
Also beware that those annoying clips that are embedded in the foam inside the seating area serve a very important purpose in holding the covers in place, so you don’t want to cut through or damage them.
Seat Cover Modification
I initially thought I would modify the seat covers the way suggested by the forum post I was following: by simply cutting the middle section out along the space between the seats – allowing for enough extra to sew back together. However after seeing how the covers were actually assembled I realized that they were designed in modular fashion. I assume this is so Benz can use the same basic cover patterns for 2, 3, or 4-passenger seats by just adding seat sections. In theory, all I needed to do is remove the middle section of each cover and sew it back together.
I looked for how the pattern repeated and selected the seams at the edge of this pattern. I busted out my handy seam ripper and separated the sections out. Here one section of the back cover is removed. When I tested the assembly of the remaining pieces, even the pattern match-marks (the little “V” cut into the edge of the fabric) matched up on the remaining pieces.
This is the back fully separated into the three sections. You can see how the two end sections will fit together. (Ignore the lines I drew on the fabric, those were from when I thought I had to cut the sections out.)
I did the same process on the seat bottom, removing the middle section.
I sewed the covers (minus the middle section) back together using my home sewing machine with heavy duty upholstery thread (the fake leather was really easy to sew). This entire process maybe took a couple hours and most of that was ripping the seams – being careful not to damage the fabric. Note that some of the seams included the plastic strips that attach to the “tuck clips” in the seat cushion. I made certain to include these when I sewed the sections together.
The re-assembly was much as you’d expect: basically the reverse of what you did to take everything apart. I think the trickiest part was getting the seat cover clips to tuck into the fittings that are embedded in the seat foam. No special instructions for this, except for simply pressing the covers at the clip locations until you hear them click in place.
The result looks pretty much like a factory seat. It retains all it’s Iso-fix attachments for child car-seats and retains the two locking latch supports of the 3-seat original. (The middle support that is removed does not lock in place.)
