We installed seats with air suspension and swivels. That combination made the seats too high for the van. So we swapped out the seat bases for lower versions.
We love the Knoedler air suspension seats we bought. It’s also really helpful to be able to swivel the passenger seat to face backwards when we are camping. To make this setup work, we needed lower seat bases.
Mercedes makes shorter seat bases. They are used with the factory swivel option and with the factory suspension seat option. We should have had factory suspension seats in our van, only the dishonest dealer sold the van we custom ordered to someone else.
The bases are about 3-1/4″ lower than stock. The handbrake moves down with the lower base, but not by the full 3-1/4″ so it might still interfere with a swivel on the driver’s side. There’s no need to re-tension the cable, because the cable/housing length doesn’t change. You just push a little more of it down through the floor grommet. We had to trim about 1/4″ of plastic off the base of the handbrake cover, but that could also be because we took the opportunity to add some sound damping under the rubber floor in the driver and passenger footwells at the same time as changing out the bases.
The seat bases come in beautiful primer black. We decided not to bother painting them, and they actually blend in better than the originals.
Installing lower seat bases
To swap the bases out, you start by removing the seats (and the swivels in our case). Do NOT put the key in the ignition while you have the seat wiring unclipped. You’ll end up with SRS warnings which may or may not need a scan tool to reset. I also unhooked the battery disconnect next to the accelerator pedal and also undid the cable from the auxiliary battery terminal under the hood.
The whole job is much easier if you remove the rubber floor mats from the van. First you have to take out the plastic panel at the top of the door step (Torx 20 screws) and the tool cover in the footwell, then you can just pull the floor mat out. The pieces behind the seats just slot in place. Give them a little tug and they will come free.
Inside the passenger seat base you’ll probably find at least one mystery box with wires coming out of it. Remove the screws attaching it to the seat base (Torx 20 or Torx 25 screw heads) but leave it wired. It can just rest on the floor while you change out the bases.
Each seat base is held in place with four bolts. The bolts have Male Torx (E type) heads, which need a special socket set. If you don’t have it already, it’s worth getting for all the other bolts on the van. The bolts are tightened down well and they have a nice coating of rubber undercoat holding them in place from below. You’ll need to give them some persuasion to work them loose.
Once all four bolts are out, you can carefully lift up the seat base and remove it.
My seat base had a couple of extra pieces inside it because I’d already run an air hose and some wires from the driver’s seat base across under the plastic raceway. If you were planning on adding wires, this is an ideal time to do it because with both seat bases removed you can actually undo the plastic raceway and fish around inside it – something that is impossible with the seat bases in place. I took the opportunity to add more cables for a subwoofer install later.
Now it’s time to install the new lower seat base. Use the same four bolts that you removed. Place it carefully over the mystery electrical box and any other wires you ran, and then bolt it down. Check carefully that you haven’t trapped anything under the perimeter of the base before you tighten it fully. I added some sound dampener and foil faced foam insulation inside the original base, and I had to make sure it didn’t get squashed under the new base as I installed it.
The driver’s side base is pretty much the same, only you have a lot more wires to contend with. Use a voltmeter to check that absolutely nothing inside the seat base has any voltage flowing to it before you start. If it does, you will most likely short it out which could mean troubleshooting either burnt-out fuses or burnt-out cables. Save yourself the hassle. Disconnect all of your power sources first.
In this picture you can see the mess you are left with after you’ve removed each component, removed the base, then carefully placed the new base over all the cables, relay bars, and fuse panels. We worked on this together to avoid trapping anything.
Our original seat base had a 12v outlet in it. We were under a time crunch and didn’t have the patience to work out how the outlet disconnected from the base. We should have spent the time figuring it out, because now we have to drill a 1-1/4″ hole in the new base while it is in place. It would have been much easier and cleaner to do this before we bolted it down. By the way – we got the outlet out of the old base by bending some of the metal that forms the shield inside the socket, so that the plastic clips that push against the opening could move back away from the opening.
Buying the right parts for the lower seat bases
Buying the seat bases aftermarket isn’t too hard. They cost around $200 each from online stores. The part numbers are A9069107300 (passenger) and A9069107900 (driver, with handbrake mount). You might need to remove the leading “A” if you’re searching online.
If you order from an online source, do NOT enter your VIN number – they’ll substitute the correct seat bases for your van without telling you (ask us how we know). Instead, just read and ignore all the stuff about how they won’t do a refund if the parts turn out to be wrong if you haven’t entered your VIN.
Also, do not expect any customer service from the online merchants. Even though they are actually Mercedes dealers (genuinemercedesparts.com is a dealership in Georgia, for instance) they have very slim margins on their online sales and their level of service reflects this.
If you are in Europe, FASP make a different replacement seat base. It’s slightly taller than the lower OEM base.
If you are thinking of adding a driver side swivel, you can buy a folding brake lever that kind of flops down after you’ve pulled it up/on. The parts you need are: 906-420-03-12 (Brake lever); 906-427-06-34 (Brake lever cover); 906-427-01-20 (Brake lever handle); 906-420-54-85 (Brake cable, 144″ wheelbase); 906-420-55-85 (Brake cable, 170″ wheelbase). Alternatively, you can leave the handbrake off while you rotate the driver seat, then put it back on when you’re done scooting it around.