TT Seats in Mk4 Golf

[Nuje]

Feels like this is about 15 years late, but since I couldn't find anything really definitive for installing TT seats in a Mk4, I figured I'd write this up for posterity, if nothing else.

First up, the issue. Mk4 VW seats mount into the car via two side rails - the seats have little wheels and sliders that run in those rails. The Mk1 TT seats, however, are more typical in that they'd bolt straight to the floor of the vehicle. And if you did bolt these seats straight to the floor of your VW, you'd be sitting very, very low.

My first thought was to find something that I could bolt to the floor and then mount the seats to that - and found (thanks to slick winter roads and people around here who don't believe in bespoke winter tires) a road sign post or two lying in the ditch that would probably fit the bill. Good and strong, anti-corrosion treatment, many holes at regular intervals. But....that would mean drilling through the floor pan of the car and hopefully not hitting anything crucial, so....

Plan B: Found some mounting brackets for just such a purpose. Not cheap however - at $185 for just one ($370, thus, for both front seats) from PlantedTechnology.com. Similar (cough-cough) options seem to also exist at significantly cheaper prices ($150 shipped for the pair) - eBay link, so it'll probably expire, but the seller is mitstocks.

Here's a video that explains (with video quality that makes you really appreciate the HumbleMechanics for the world) the basic functionality and installation process in a Mk4.

Given that both 5'11" me and 5'4" Mrs. Nuje (maybe?) will both drive this car, I wanted some seat adjustability and the TT seat rails have front anchors that pose a bit of a problem, some metal-moving had to occur.

The TT seats front bolt anchor points are bent forward at a ~45° angle, and gusset-reinforced.

So, out came the M18 angle grinder with cutting wheel and we hacked away that gusset.

Then, I supported that end of the rail by jamming a piece of 2x4 between the rail and the seat bottom and hammered the formerly gusseted extension flat.

At the other end of the rails, there's a locater pin that extends upward and just barely gets in the way (or not quite) of that mounting plate (sorry - no photo, but you'll know what I'm talking about if/when you get to this), so I ground away a bit of the corner - like maybe 2mm in each direction, just so I had a little wiggle room if needed.

After that, it was just a matter of figuring out how to bolt it together. I went with a heavy-duty washer (the ones that come with the 6point axle nut work great) on that gusset-removed area, along with the bolts/nuts from bottom mk4 shock mount (M10x1.5). You can't mount the plate directly to the seat rails because the spring-guided pins that lock the seat in place when you adjust front/back need roughly 5-8mm of headroom.

So, I stacked three M10 washers between the plate and the rails. At the front (gusseted) end, I went with the bolt head through the rail, through the washers, through the plate, then another washer and then the M10 locking nut. There was maybe 20mm left sticking out, so I just cut those off with the cutting wheel.

At the back (notch-cut) end, I re-purposed the M10 washered bolts that hold the Mk4 upper rear shock mounts - perfect length and should be plenty strong. Same M10 locking nut as the rear bottom shock mount. At that end, I put the bolt through the bottom of the mounting plate, then used a magnet to get the nut into position (it's inside the seat rail, so space is at a premium), then wedged a screwdriver in there to counter hold as I tightened the bolt.

Finished product looks like this from the bottom (back is up top, front of seat at the bottom). You can see the locating pins that are kinda / maybe in the way in this photo; maybe didn't need to grind anything away, but in dry-fitting things, having a little room to move helped.

The little tabs at the bottom mount up behind the lip where the OE seats bolt; for the rear, there are two little "tongues" that slide into the car's seat rail side "slots", and then again, those rear upper shock mount bolts are the perfect length and threading to lock those in place.

Wiring:
The good news is that the wiring is the same on these seats as in the OE seats.
The bad news is that the wiring connectors for the airbags and seat belt tensioners/locks (or whatever that other one is for) are different. TT on the left (seat side), Mk4 Golf on the right (car side).
Green connector is the seat heat (no change necessary); red is the seatbelt thingy (two wires on passenger side, four on driver side); yellow is the airbag (three wires on each sides). The colors matched up, so it was pretty straightforward. (Of course, I stood back when I first turned the key; YMMV )

At first I thought I could just pull the terminals and move the existing wires to a VW Mk4 connector, but alas, the wire terminals are different shaped between the two cars. So, it was snip-and-heat-shrink-butt-connect.

The finished product:

 

[Nuje]

Spoke too soon.
Finally got the plates for this car and took it out for a drive and within 5min, got a AIRBAG fault code.

                Address 15: Airbags       Labels: 6Q0-909-605-VW5.lbl
Control Module Part Number: 1C0 909 605 F
  Component and/or Version: 08 AIRBAG VW61 0202 0001
           Software Coding: 12344
            Work Shop Code: WSC 00000 
                      VCID: 271E3780C72506ABAA-513C
2 Faults Found:
00592 - Seat Belt Switch; Passenger (E25)
            33-10 - Resistance Too Low - Intermittent
00591 - Seat Belt Switch; Driver (E24)
            33-10 - Resistance Too Low - Intermittent

"Resistance too high" I've seen and dealt with before, but "too low"....? Might have to scrounge some seatbelt latches from a true Mk4?

Any ideas on how to address this? Tie a resistor of some sort into the wiring...?

Does anyone know what exactly that "switch" does? I know there's an explosive pre-tensioner or something in the actual seatbelt reel, but the latch on the seat...? What does it do in the event of a collision?

 

[Zak99b5]

I think the latch switch just lets the air bag controller know it’s buckled. Weird that it’s reading resistance value though.

 

[PakProtector]

First thing comes to mind is measure the Mk4 latch's switch and the TT's switch. Do *NOT use a DMM Ohm-meter. It will take a volt meter, a resistor and a battery. Suggest 10 Ohms, and use the car battery. Then measure battery voltage, resistor voltage and switch voltage. Use Ohm's Law to calculate current, and then resistance of the switch. Measure voltage across the 10R resistor, and voltage across the switch.

Douglas

 

[Nuje]

I think the latch switch just lets the air bag controller know it’s buckled. Weird that it’s reading resistance value though.

Good to know - makes sense. So doing what I found (next post) won't impede any safety functionality given that latching the seatbelt is an automatic whenever driving.

 

[Nuje]

First thing comes to mind is measure the Mk4 latch's switch and the TT's switch. Do *NOT use a DMM Ohm-meter. It will take a volt meter, a resistor and a battery. Suggest 10 Ohms, and use the car battery. Then measure battery voltage, resistor voltage and switch voltage. Use Ohm's Law to calculate current, and then resistance of the switch. Measure voltage across the 10R resistor, and voltage across the switch.

Douglas

Thanks for the instructions - kinda what I'd had in mind (without knowing any specifics of how exactly to do it, so your reply was exactly what I was looking for. Until....).

But then I came upon this thread at Vortex where someone posted how to just connect the positive/negative wires across a resistor and be done with it. 470Ω on the driver-seat wires, 2.2kΩ on the passenger-seat. Ordered a multi-pack of resistors to give it a try. If not, then it's back to Douglas's how-to above.

 

[Nuje]

Following up on the preceding:
Driver-side of the car was in the shade yesterday, so tackled that side first.
Put in the 470Ω resistor inline between the ground and positive wires on the car-side. Cleared the fault codes to check/hope that the driver one wouldn't come back and....neither came back.
Didn't have to do the passenger side. Drove for at least an hour since with a dozen or so starts and seems to be holding.
Haven't had a passenger in that seat yet (using the seatbelt latch), so hopefully that doesn't change the equation.
EDIT: Turns out this matters. See post #10 below.

 

[Fahrvegnugen]

Nice your resistors came fast! Happy seating. Who knew it’d require ohms law. I want laws to keep their distance. However I might do well to learn Ohms equation. But tt seats probably are worth it.

 

[JHands]

How much vertical did this mounting system add? As in, with the TT seats all the way down, how much higher, if any, is the center of gravity compared to any of the MK4 golf/Jetta seats with seats all the way down?

 

[Nuje]

Follow-up to my post #7 above:
"Put in the 470Ω resistor inline between the ground and positive wires on the car-side. Cleared the fault codes to check/hope that the driver one wouldn't come back and....neither came back. Didn't have to do the passenger side. Drove for at least an hour since with a dozen or so starts and seems to be holding. Haven't had a passenger in that seat yet (using the seatbelt latch), so hopefully that doesn't change the equation."

Narrator: It most certainly did change the equation.

As soon as I had my wife along in the passenger seat and she buckled up, the airbag light came on.
(A smarter person would've checked this before being rushed to catch a ferry to drop the car off to my parents for a couple weeks.)

I quickly looped back to the house, though, grabbed the bag o' wiring stuff, the box of (now 398) resistors, and drove a little faster to make the ferry on time. Then was able to get under the seat (didn't have to remove any bolts) and snip the wires and run the 2.2KΩ resistor between them.

Cleared the codes and then drove off the ferry and the rest of the trip with no airbag warning lights.

 

[Nuje]

How much vertical did this mounting system add? As in, with the TT seats all the way down, how much higher, if any, is the center of gravity compared to any of the MK4 golf/Jetta seats with seats all the way down?

@JHands asked some other questions via pm, so I'll include answers to those things here for anyone else who might be looking at this.

Seat height: I haven't measured, but with the seat in the lowest position possible, it doesn't feel like it's much higher (if any) than the stock seat. With that said, I always had the stock seat cranked up a couple pulls of the lever. When I do lower the TT seat all the way, it does feel WAY too low for my liking, though. So....I'd say it's at least close.

I will mention, though, that at 5'11", I need to have the seat slid almost as far forward as it goes. That could be mitigated to a reasonable extend by moving the front mount point from behind the lip that sticks up from the car body, to being in front to it. But (a) it fits me and I'm the only one who's gonna be driving it; and (b) it's not the stock way of setting things up, so I figured, why mess with "good enough".

The other question asked was around the airbags / resistors:
The main reason I wanted to fix the airbag light was that, from what I recall reading, if there's on airbag fault, it disables the full airbag / SRS system.
Maybe true, maybe not, but I'd rather have a fully operational safety system either way.

The fault code was simply indicating that the resistance across those wires (running through the seat belt latch) wasn't what was expected, so it fired off the error. The reasoning being that if the seat occupant isn't wearing a seatbelt, it won't fire the airbag as the airbag can do a lot of damage to a human body that isn't in the position expected by the design of the airbag explosion.

We always wear seatbelts (I feel something akin to naked without one nowadays), so I don't feel like I'm defeating a safety system with my workaround.

 

[JHands]

@JHands asked some other questions via pm, so I'll include answers to those things here for anyone else who might be looking at this.

Seat height: I haven't measured, but with the seat in the lowest position possible, it doesn't feel like it's much higher (if any) than the stock seat. With that said, I always had the stock seat cranked up a couple pulls of the lever. When I do lower the TT seat all the way, it does feel WAY too low for my liking, though. So....I'd say it's at least close.

I will mention, though, that at 5'11", I need to have the seat slid almost as far forward as it goes. That could be mitigated to a reasonable extend by moving the front mount point from behind the lip that sticks up from the car body, to being in front to it. But (a) it fits me and I'm the only one who's gonna be driving it; and (b) it's not the stock way of setting things up, so I figured, why mess with "good enough".

The other question asked was around the airbags / resistors:
The main reason I wanted to fix the airbag light was that, from what I recall reading, if there's on airbag fault, it disables the full airbag / SRS system.
Maybe true, maybe not, but I'd rather have a fully operational safety system either way.

The fault code was simply indicating that the resistance across those wires (running through the seat belt latch) wasn't what was expected, so it fired off the error. The reasoning being that if the seat occupant isn't wearing a seatbelt, it won't fire the airbag as the airbag can do a lot of damage to a human body that isn't in the position expected by the design of the airbag explosion.

We always wear seatbelts (I feel something akin to naked without one nowadays), so I don't feel like I'm defeating a safety system with my workaround.

Hey brother. Thanks for the reply. It’s hard to tell from the photos, but can you mount the seat at different positions on the frame relative to the front and rear of the vehicle? My wife and I drive the car, and she’s shorter than me by a bit, plus prefers to drive it like a go kart. I need the range of forward/backward adjustability if I’m going to try to tackle this install.

By mounting the plate forward of the lip, are you referencing the lip where the two nuts connect to the front of the slides on the OEM seats? Wouldn’t that only give you the difference of the thickness of the metal?

 

[Nuje]

By mounting the plate forward of the lip, are you referencing the lip where the two nuts connect to the front of the slides on the OEM seats? Wouldn’t that only give you the difference of the thickness of the metal?

Yes - that's exactly what I mean. But I was thinking you could also use some longer bolts as well as some spacers to gain maybe an inch or so. I don't know how robust this would be, so you'd be on your own there. Keep in mind what forces would be acting on the front seat in the event of a forward impact....I don't know that a bolt would hold that (it is bolted down quite solidly in the back)....maybe an engineer can chime in and help out.

As for how the seat rails bolt to the frame, there are a lot of cut-outs in there - I just chose what seemed to fit best with what was pre-existing and hoped that it'd fit. I was at least half-expecting that I was gonna have to take them off again and do some adjusting but the "close enough" turned out to be close enough for me.

If I knew my wife was going to be driving the car regularly, I'd figure out a way to mount things further forward on the bracket.
You can see on the image below that there's plenty of room to move the bracket further upwards (effective moving the seat closer to the steering wheel when installed).

You wouldn't use those angled gusseted bolt holes that I discussed early in my post and instead use a set of them further back. Might have to drill a couple holes in the bracket depending on where your attachment points line up, and where those alignment pins (red arrows above) are protruding but I'm pretty sure it'd be do-able.

Just do it when you have a spare seat in the car and thus don't have time pressure to get it finished, start on the passenger seat to see what's what, and I think you'd be fine.

 

[JHands]

Yes - that's exactly what I mean. But I was thinking you could also use some longer bolts as well as some spacers to gain maybe an inch or so. I don't know how robust this would be, so you'd be on your own there. Keep in mind what forces would be acting on the front seat in the event of a forward impact....I don't know that a bolt would hold that (it is bolted down quite solidly in the back)....maybe an engineer can chime in and help out.

As for how the seat rails bolt to the frame, there are a lot of cut-outs in there - I just chose what seemed to fit best with what was pre-existing and hoped that it'd fit. I was at least half-expecting that I was gonna have to take them off again and do some adjusting but the "close enough" turned out to be close enough for me.

If I knew my wife was going to be driving the car regularly, I'd figure out a way to mount things further forward on the bracket.
You can see on the image below that there's plenty of room to move the bracket further upwards (effective moving the seat closer to the steering wheel when installed).

You wouldn't use those angled gusseted bolt holes that I discussed early in my post and instead use a set of them further back. Might have to drill a couple holes in the bracket depending on where your attachment points line up, and where those alignment pins (red arrows above) are protruding but I'm pretty sure it'd be do-able.

Just do it when you have a spare seat in the car and thus don't have time pressure to get it finished, start on the passenger seat to see what's what, and I think you'd be fine.

The one question I forgot to ask…will this work with the mk4 arm rest in place? Do you feel there is room between the bolsters?

 

[Nuje]

Oh yeah - there's plenty of room for the armrest. Pretty close to the same amount of gap for you to drop stuff next to the parking brake plastic, but not nearly enough to get your hand down there to fish it out.