Yellow connectors are part of the air bag system. Don't apply a voltage to any wires going to a yellow connector. If you power the wires going to the bag igniter, the bag will deploy.

I'd get hold of the schematics for both models and figure out what goes where by following the diagrams.

I'm just guessing here but one modal may have a "seat-occupied" sensing switch that the other doesn't. One modal may have a "belt-latched" sensing switch that the other doesn't.

 

They sure look like airbags to me. However, the seatbelt wire is also a yellow plug. Trace it down from the buckle. Should only be a 2 wire plug

 

The B5.5 seat has two yellow connectors, the airbag one has a spring loaded connector and has the same wiring colors as the B5 connector shown in the second picture (Brn, wht, grn). I only took a picture of the seat belt one as it the only one I have a question on.

In the bottom picture the red is the B5 seat belt and the yellow is the airbag.

I probably should have been a bit clearer and taken a few more shots (I didn't take any of the seat belt plug itself) - it was late and a few beverages were involved. The top picture is the floor connector for the B5.5 and does match up with the seat belt (traced them out to make sure it wasn't the airbag one). The B5.5 seat belt does also have 4 wires.

I would guess based on the lack of threads I found, most have just swapped over the B5 seat belt. I'm going to pull out the multi meter and take some readings on the pairs of wires with the belt attached and see which ones give me a closed circuit and try splicing in the B5.5 harness into the floor harness. Worst case, I'll have to swap over the B5 belt.

I'll document what I come up with as it may help someone else in the future.

Thanks

 

Careful. The seatbelts have explosive tensioners; even putting a meter on the connectors may be sufficient to set them off. At least one member has been injured that way.

 

I saw that thread when I was searching. What I'm going to measure is the seat belt buckle end. I'm assuming there is a contact switch in the buckle. I'm going to use the B5 seat belt buckle first, attach the seat belt and see what I read across the two wires, I should see a closed connection.

I'll do the same with the B5.5 buckle and see what I read across the two pair of wires.

I've already disconnected the battery, and going nowhere near the tensioner in the door pillar, everything I'm doing is on the seat buckle itself.

 

As scotts13 said; I suggest you use the wiring diagrams to determine which wire connects to what.

 

Swapping the seat belt pieces from the B5 to the new seats, is exactly what I did. I simply removed the tear drop piece, by unscrewing it. There is a crush washer under it, that needs to be replaced to put the new one on. It is really that simple. I have seen threads where they will break that piece off and flip it around. I have had my seats in for about a month, and have had zero problems with the seat belts.

 

Shaggy, saw that in multiple threads. As we also swapped out the center console as well, I'm leaning toward trying to keep the B5.5 buckle as it is about 1.5" taller than the B5 one and should be a little easier to work with the new console.

So I'll try to document what I'm doing in case it does work....

Here is the B5 Seat Bottom (original seat),

Original floor harness

Here is the B5.5 Seat bottom; you can see there are two yellow connectors, one is spring loaded for the airbag - the other is the seatbelt. (Note this seat is heated, the original wasn't - I'm going to wire that later when I have to work under the dash).

Although my line drawing skills suck, and black on black doesn't show well - you can see the seat belt wire going to the connector;

Here is the B5.5 floor wiring harness, the airbag uses the same wire colors as the B5 airbag, so that one is straight forward. You can see the second yellow connector for the seatbelt and the 4 wires, two of which have the same colors as the B5. The Green is for the heated seats. I have the switches and the dash connectors, I'm just debating on building the harness or buying one (found one on line for $58, which may be a better option than building one).

Thought I'd get this posted, I'm going to put the original seat in and take some readings with a multimeter and then do the same with the B5.5 seat. If I can identify the correct wires, I'm going to splice the new connectors into the floor harness.

More to follow.

 

Well after all the searching, this actually turned out to be no big deal.... I actually think this is a better approach than swapping over the B5 seat belt to the new seat.

I guess I should put a disclaimer, follow this at your own risk. Before you start, disconnect the battery. Also before touching the airbag connector, touch some metal to discharge any static electricity. If you set off your airbag, you're on your own.

So first task was seeing what the seat belt connector shows with buckle inserted. I pulled the connector to the top of the seat to make documenting this a bit easier. With out the buckle inserted, it showed a closed connection (I was expecting an open circuit, but thinking about it it makes more sense). (Note the nasty original seat)

I then inserted the buckle and inserted the buckle and it showed an open circuit.

Next was swapping in the new seat and doing the same thing with the two pairs of wires;
The Brn - Brn/Red was first as these were the same colors as the original seat. Note I had the pigtail from the donor car, so it made it easy plug the connector in and use the pigtails. The wires going to the seat buckle are actually 4 different colors.
With no buckle, I also showed a closed circuit like the original seat.

And with the buckle inserted, an open circuit - so these were the wires I needed to splice in. As they were the same color, I could have assumed it was the same function, but wanted to make sure.

 

I also decided to check the other pair, the Brn - Red that were twisted together.
They showed two different resistance values, may have to find some wiring diagrams for the B5.5 to see what they're for - but as I didn't need that circuit, I wasn't really worried about them.

So now that I had the correct two wires, I simply spiced in the air bag connector and seat belt connector. The air bag uses the same colors, so not a big deal. A bit of solder and shrink wrap and good to go.

Some friction tape, and looks almost stock.

 

Oh the passenger side, there is no seat belt connector on in the B5, so the only connection to worry about was the airbag.

Soldered and shrink wrapped.

The end result, no seatbelt or airbag light and no pyrotechnics...

I really think the B5.5 belts work better as they are taller and bend a bit - particularly with the B5.5 center console.

Hope that someone else finds this useful.

 

Now I want the taller seat belt connectors too! I've had several people unable to buckle the passenger side since I added the B5.5 center console. I never realized the B5.5 had them.

 

That was reason I wanted to take this approach, given that they are about 1.5" longer and have some flex. I had seen some comments where people had problems with the B5 belts after upgrading the console.

I was going to try this today if I needed pull off the old seatbelt. Most seem to disconnect the bolt on the tear drop part (and dealing with a crush washer and such), but I was going to try to remove it by the M8 triple square fastener on the bracket. As I didn't need to remove it, I didn't try. But thought it would be easier than the normal way.

 

Nice job!

 

The piece you have circled in green, is the one that I removed to swap out the seat belts on my seats.

 

The threads I saw removed the other one, but thought the one I circled would be easier.. thanks for confirming that. Now you just need some B5.5 belts..

 

would really help if i could see the pictures posted, anyone know why i cant? im trying to swap mk6 gli seats into my b5.5 and having trouble m figuring out what wires are which as the mk6 only has 2 wires and the b5.5 has 4?????