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Discussion Starter #1 (Edited)
Have a set of Recaro seats from a 13-14 car, but you have a 2015+ and want to use them? I found myself in this situation. Unfortunately, there are plenty of people commenting casually "...the sensors are all the same..." and "...the wiring just needs to be spliced...", but no how-to. Here, I will describe how I accomplished this swap, and some of the issues. Sorry it is light on pics, but most is self explanatory. I did NOT deal with getting the heated seat function to work, but I did get the drivers side power working. Personally, if I had to do it over again, I would wait and buy seats appropriate for the year and avoid the headache. Its not too bad a job, but some changes need to be made to make them work...read on.

First, THESE INSTRUCTIONS INVOLVE MESSING WITH YOUR AIRBAG WIRING. I AM NOT RESPONSIBLE FOR ANY MISTAKES YOU MAKE OR DAMAGE YOU MAY DO TO YOUR CAR OR RESTRAINT SYSTEM. Now that is out of the way,

Parts I used:
FU5Z-14A699-GCA ~$30 Driver or passenger 15+ ST3 seat harness
FU5Z-14A699-GAA ~$30 Driver or passenger 15+ ST3 seat harness (I can't remember which is driver or passenger but you need both)
Lots of various size zip ties
A scratch awl or large screwdriver
Needlenose pliers
2 splice butt connectors, or soldering iron and solder

Optional (you can harvest these from your ST1 seats, or buy new):
EU5Z-14K155-F ~$65 Airbag harness jumper wire passenger side
????? ~$65 Airbag harness jumper wire drivers side (I ended up harvesting mine from my drivers seat)
Cut body to seat harness from the drivers side on the donor 2013. If you don't have this, you will have to cut two wires on the 2013 ST3 seat for seat power.

First, lets dispel the myth that the sensors are all the same - they are not. Comparing part numbers between years show that the airbag control module,
and the seat position sensors are not the same between 2013-14 and 2015+. In addition, the passenger occupancy sensor gel pad is not the same. The gel pad issue can
be resolved by swapping those between seats. The seat position sensors are different, but the old style appears to work on the 2015+. The purpose of this sensor is to tell the airbag module how close the driver or passenger is to the dash. If one is too close to the dash (as detected by the sensor), the airbag will not deploy or deploy with a reduced
force in a low speed collision. In 2013-14 seats, the sensor looks like this (square thing with wires on the left):

When the seat is brought forward enough, the sensor will be over a metal tang and the voltage through the sensor changes going to the airbag controller.In contrast, the 2015+ sensor rides along the seat rail with a specific air gap (the thing with the blue end):

When the seat is beyond a certain position forward, the airgap changes (the magnetic force is changed in the switch) altering the voltage to the airbag controller:

On the surface, these designs are flipped. In 2013-14, the sensor in a non forward position is not over the metal tang, whereas in 2015+ the sensor is alwayos
next to metal. I am making the assumption they are sending the same signal to the airbag controller. For some electrical engineering type person out there, bench testing these sensors should be able to determine this, but I don'tknow how to do it (what voltage supply to use, correct test leads, etc). It is also not wise to go probing around the live airbag system with a dvom trying to read the voltages of these sensors either. Whatever the case, I used the 13+ seat position sensor and I got no airbag light. I am making the ASSUMPTION that these sensors work send the same signal to the airbag controller. FYI, you cannot mount the 2015+ seat position sensor to the 2013 seat as the seat rail design is completely different.

So, lets start with the drivers ST3 seat. You have 4 things you want to take care of:
1. Seat buckle
2. Side airbag
3. Seat position sensor
4. Seat power.

Taking these in order:
1. The seat buckles mount the same with the same torx bit on the 13-14 seat and the 15+. I chose to transfer my current buckle to the ST3 seat. If your seats are from a wrecked car, this may be a wise decision. You should have a plug on the new driver side seat harness you bought that matches the buckle plug. Plug it in, and arrange the wiring in a way that it is secure (cue the zip ties).
2. The side airbag is wired on the 2013-14 ST3 seat to a junction box under the front of the seat into which the body harness plugs into:

In contrast, the 2015+ seats (ST1, ST2, ST3) have a jumper wire that goes from the side airbag that plugs into a connector coming from the seat harness (look under your ST1 seat at the yellow plug and you will see what I mean). This pic is the connector from the seat harness on a 15+ that goes to the airbag jumper wire:


Obviously that won't plug into the junction block on the 2013-14 seat. Ever look at those airbag terminals at the connectors? They are gold plated, and the wires are 22 gauge. Resistance is very important in these circuits, as is the length of the wiring to the airbag. Therefore, making a splice repair in this circuit is a bad idea. It may work, or it may fail. The best solution is to harvest the airbag jumper wire from your ST1 seat and use it on the ST3 seat. To do this, you will need to fold up the upholstery to get at the connector. When you can visualize it:


...use the needlenose and pull down on the orange portion and the wiring will disengage from the airbag. Take this jumper harness you removed from the ST1 seat (or bought new) and slide it up next to the existing wiring on the ST3 seat. I chose to unplug the ST3 airbag wiring, but leave it in place. Plug your ST1 jumper harness into the ST3 airbag and route it down under the seat (with needlenose, push the orange portion of the connector up to lock it into the airbag). Zip ties are your friend here. Plug the end of the airbag jumper wire into the yellow plug of the ST3 seat harness you bought. There is a little red locking tab to lock the connection. Now you should have the buckle and airbag plugged into your ST3 harness.

3. Unplug the exisiting ST3 harness going to the seat position sensor, and plug in your new ST3 harness to the seat position sensor. Now you should have the new harness plugged into the seat buckle, airbag, and seat position sensor.
4. Lastly you need to take care of seat power. Find the black/white and purple/red wires corresponding to slots 16 and 21 of the ST3 seat harness you bought. Cut them and solder the black/white wire to the black/purple wire going to the bottom of the ST3 seat junction block (see picture below), and solder the purple/red wire to the yellow/red wire going to the middle left of the ST3 junction block (see picture below).



If you don't have the cut body to seat harness from the 2013-14, you will need to cut the wiring behind the junction block on the ST3 seat. I am not sure if the wire colors change behind the block or not - just make sure you splice the right ones.. That takes care of seat power.

You should now have a few random plugs on your new harness. These are for heated seats and seat power switches, but I did not use them (and you shouldn't need them for seat power if you did what I did). Just find a way (zip ties to securely get them out of the way). Arrange all the wiring underneath the seat in a way it won't get caught in the seat rail or have a rear passenger hit it with their feet.

Now, lets move to the passenger ST3 seat. You have 4 things you want to take care of:
1. Seat occupancy sensor
2. Side airbag
3. Seat position sensor
4. Seat buckle


1. The passenger occupancy gel sensor is of a different design between 2013-14 and 2015+. In both cases, it seems to mount in a similar same manner. I chose to swap my 2015+ sensor into the2013-14 seat to alleviate the chance of any codes. I don't have the factory manual, but I have not seen evidence of a zero weight test needed for this gel pad type of sensor. That is basically
a test that you run on the passenger seat to calibrate when you first install it so it reads the weight correctly and turns the airbag on and off with the correct weight, but you needVCS and IDS
software to do it.Anyways I don't have the manual, but I don't think you need to worry about it. Anyway, you need to remove the sensor from the ST1 seat to swap it into the ST3 seat. On both seats, you need to free the wire "basket" under the seat from the bar on the back of the seat. Once that is free, the gel occupance sensor won't come out of either seat because it has two clips under the upholstery that hold it in. This is a picture of the ST3 seat, but the ST1 is similar. You need to lift up the upholstery and free those clips and the sensor should slip out.




The black clips on the front of the ST1 sensor are in a different place however (ST3 seat position pad pictured above, you'll see the difference from the ST1 when you remove it). Carefully use a scratch awl or screwdriver to make two new mounting holes in your ST1 gel pad to have it mount securely in the ST3 seat. MAKE SURE YOU DON'T PUNCH THROUGH THE GEL PAD. There is plenty of plastic you can punch through to avoid the gel pad. Once that is done, insert and install the ST1 seat occupancy sensor in the ST3 seat in the order you removed the original one. There is no convenient way to mount the sensor plug as it was before. Get creative with the zip ties. Then, find the plug on your new harness and plug it into the occupancy sensor.
2. Follow the same procedure as the driver side seat.
3. Follow the same procedure as the driver side seat.
4. Follow the same procedure as the driver side seat.

Now, you should have the driver and passenger seats all wired up. You should have spliced zero wires with the exception of the power to the seat motors on the drivers side ST3 seat. I did not disconnect my battery, but just unplugged each seat and installed the new ST3 seat.In retrospect, it would have helped to wrap the seat mounting legs in towels as I got a few scratches on some trim when trying to reinstall them (fitment is tight, and the ST3 seats are much heavier than the ST1 seats). When I started the car, I had no airbag light. When no one is in the passenger seat, the airbag is off; when I sit in it with the car running, the airbag is on. I have not tried with my co-pilot, Captain Kirk the Chihuahua to see if it stays off when he sits in it, but I expect it will function fine (it should not come on while a small dog is in the seat). Here is a picture of the wiring under the driver seat:

and passenger seat:


The finished product:

Improvements to this procedure would be:
1. A definitive bench test of both seat position sensors to confirm they work the same
2. Torque values for the seat buckle torx bolt and the seat base bolts
3. Figure out the seat heat wiring

I hope this helps others out that are trying to do this swap! If you have a more efficient way to do any of these steps or a better method, please provide it to help out the community.
 

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@Fuxalt, this would be great in the guides/how to section since it will quickly get buried in the general discussion forum.
 

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Discussion Starter #3
@Fuxalt, this would be great in the guides/how to section since it will quickly get buried in the general discussion forum.
I agree. I should have posted this in the guides section. I see this question about the 2013-14 seats come up fairly often and I think this should help somebody out. How do I contact a moderator to move this thread to the Guides and How-to forum?

Thanks -
 

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So in theory wouldn't st2 seats be an even easier swap? Basically just swap the gel pad for the weight sensor in the cushion on Passenger side right?
 

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The seat belt buckle torque is 47 Nm, seat bolts are 35 Nm. You should also disconnect the battery and remove Fuse 86 (10A) before fiddling around with things that have airbags.
 

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This seems a lot more difficult than the way I did it, all of the connectors into the sensors are the same so I just gutted the wiring from my 17 ST1 seat and hooked it up in the 13-14 ST2 seats. Also swapped seat belts, gel pad, and oscm


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Discussion Starter #7
Its the same as what you did, except I had 15+ ST3 seat harnesses (that came with the seats and the PO had purchased) so I didn't have to gut my ST1 seats.
 

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Its the same as what you did, except I had 15+ ST3 seat harnesses (that came with the seats and the PO had purchased) so I didn't have to gut my ST1 seats.
So out of curiosity, do you think I would be able to do the opposite of this? I found a guy online that wants to trade his 14's ST3 seats for the ST1 Seats my 2017 has... would you say the best thing to do in this situation would be?

Really appreciate your help on this! Thanks!
 

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I just swapped some 13-14 ST2 seats into my 2015 ST1. I stripped all of the wiring from the ST1 seats and transferred it to the ST2 seats. This required upclipping and peeling back the upholstery of all the seats to access the airbag wiring. The occupancy sensor needs to be swapped as well on the passenger seat but the gel pad itself doesn’t need to be swapped and is nearly impossible to remove from the ST2 seat.
 

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If you're installing ST3 seats from a 2015+ model into an ST1 which is also a 2015+ do you still need to swap out the occupancy sensor?
 
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