Adding ventilated seats to Active Comfort heated seats?

**serious7series** · 08-14-2014, 03:23 PM

I have the heated Active Comfort Standard in my 2000 750iL. Having them cooled or ventilated would be a nice touch. I've read through some threads here on BF, but none have been able to confirm if it's possible. One idea that came to mind is the BMW E39 upgrade kit (part# 82300142328 or 82300142329). Has anyone tried this? Any input would be great.

If this kit won't work, what about retrofitting a universal kit (which would require replacing the seat cover inserts with perforated leather)?? Something like this:
http://www.seatcomfortkit.com/servle...-System/Detail

Link to the E39 upgrade kit:

http://bmwfans.info/parts-catalog/E3..._retrofit_kit/

Link to the BF thread:

http://forums.bimmerforums.com/forum...d-cooled-seats

**pizzaman09** · 08-14-2014, 09:38 PM

Typically those seats use perforated leather, of which I have never seen on an e38. Also the air bags for the active seats and lumbar would likely be in the way as well. It would not be a simple retro fit, that is for sure. It would likely include a very custom seat build. It would be interesting to see, you would probably want to copy a more modern seat. The other option would be to see if e65 seats can be retrofitted into your e38. I want to say that somewhere I remember seeing someone that did that but it has been a while. Also mounting the controls would be difficult since e65 seats had the seat controls on the center armrest.

**racer2086** · 08-14-2014, 10:35 PM

I thought the E39 seats were the same/very similar? By the same token, if they would work, I don't know why BMW wouldn't have offered the retrofit for the E38.

I think you would have the best shot at getting the E39 retrofit to work on the E38 seats. The seats themselves aren't very complicated, it's just a matter of getting all that stuff to fit. Does the retrofit come with the leather? I think that's going to be the hardest part, no matter what route you choose...the perforated leather is a tough one. May have to have an upholsterer make you some custom seat covers.

I retrofitted heated seats into mine. That was hard enough as it is. I told myself I wouldn't do anything like that again. I wish you the best of luck on this project...I don't think it'll be easy at all...

If you have any seat related questions, I'll try to help, since my heated seat project is still semi fresh in my mind...

**chrisn7** · 08-15-2014, 09:27 AM

I do have a .pdf document to do this retrofit - tried an attachment but it showed as an image? If there is no other way, pm me with an email address...

I have not tried this install, but it involves cutting 4 holes in both the seat squab and backrest foams, to insert the 8(!) motor/fan assemblies. The seat is accessed by removing the leather; the back by removing the rear cover and not the leather. There is a harness to the seat trim button area and glove box area. No coding required.

Having changed the squab foams in mine to retro the active seats, I can tell you its not a fun job....but that's another story

**Flying740iL** · 08-15-2014, 09:56 PM

This would definitely have a lot of cool factor. However, I find with tinted windows and a windshield reflective shade, the seats aren't that hot and the air conditioning gets things comfortable quickly. Heated seats are far nicer to have.

**shanecarmaster1** · 08-16-2014, 03:29 PM

I do have to say, to have the modern day, proper seat perforated with 18 or 20 fans (whatever crazy amount they use) is far more desirable than a few fans probably blowing hot air in a few concentrated areas. The kit seems sorta seedy.

**serious7series** · 08-21-2014, 02:56 PM

Yeah, I may have to have an upholsterer swap in perforated inserts.

Does anyone have a spare or broken Active/Comfort seat cushion that they'd like to donate for experimentation? I'll gladly cover the shipping costs. I'd be happy to report my findings here on the BF if someone has an extra cushion or seat bottom.

**Lamer321** · 01-26-2016, 03:29 PM

bringing this thread back to life!

has anyone taken this to the installation level yet?

has anyone ever considered removing the "active" bladders (leaving the wiring harness in place) and installing the fans powered by the "active bladder" harness? this way you don't have to run wires and you have a stock button installed. Giving you heated and vented seats...

I live in Houston and let me tell you, vented seats are FAR more desired than heated...although in this case the heated portion would still remain...

how beneficial/desired is the "active" seat feature anyways?

**serious7series** · 02-09-2016, 03:28 PM

I may have found an upper seat cushion for sale. I'm going to experiment on it, since the upper is easier than the lower (no massage bladders).

**Dan750iL** · 02-09-2016, 05:12 PM

I saw a link in E38.org for adding active comfort to sport seats but never seen anything about cooling. That would be sweet.

**Lamer321** · 02-10-2016, 07:46 AM

I think it would all depend on the type of seat heating pad you had in the seat....if you wanted to keep the seat heater in the first place....This is what I discussed in another thread, but no one has replied yet...

Trimming the heating element pad? specifically around the heating wire itself? (...to make openings for potential ventilation fans to blow air through...) It would appear that the only benefit of that material is to keep the pad in place and reduce movement. I would imagine that some adhesive would suffice.

The cutting would be done throughout the entire heating pad and would be much more precise then what is detailed below but you get the idea....cut out the red areas to open up the passage of air...

it should be noted that I have the active comfort seats and would not have to deal with the "hills and valleys" of the sport seats and may be easier to manage.

a second note should be that the active seat bladders would be removed (maybe), and I would utilize the wiring harness to power the fans. and as a result have stock switches on the console to operate the fans

a third note would obviously be that I would need to have perforated leather swapped into the seats in order for this whole plan to be effective.

finally a fourth note would be that I intend to do this to both the front and rear seats, all the while maintaining the heated option (depending on the type of heating pad that the seats have)

I am very interested to hear opinions and thoughts on this as I live in Houston the idea of vents far outweighs the idea of heated seats...

**chrisn7** · 02-10-2016, 07:49 AM

[QUOTE=Lamer321;29061533]bringing this thread back to life!

has anyone taken this to the installation level yet?

has anyone ever considered removing the "active" bladders (leaving the wiring harness in place) and installing the fans powered by the "active bladder" harness? this way you don't have to run wires and you have a stock button installed. Giving you heated and vented seats...

QUOTE]

Its not quite that simple. The bladders act on a board moulded into the bottom of the seat foam, so you would need to replace the foam. Why not just remove the board? Well, believe it or not, the seat springs are different too, and shaped to match the board, with a downwards v shape in them. Not changing the springs would leave the seat with a baggy, collapsed look. Also the non active seats have an across the seat metal link between springs, to stop you sinking between the springs. On active seats, this function is provided by the bladder assembly which is clipped to the springs, keeping their positions.

Wiring: the switch centre buttons for active seats just provide a signal to the active seat module, not a switched power supply, and the wiring is completely inadequate for all those fans. Forget the switch centre - its not codable, you can't add switches, nor move them around and is chosen to suit the cars equipment, which then determines if it is diagnosable or not. Since there is power to the seats, it would be easier and simpler to acquire the correct switch and fit into the blanked off position in the seat trim

**Lamer321** · 02-10-2016, 08:01 AM

Originally Posted by chrisn7

Its not quite that simple. The bladders act on a board moulded into the bottom of the seat foam, so you would need to replace the foam. Why not just remove the board? Well, believe it or not, the seat springs are different too, and shaped to match the board, with a downwards v shape in them. Not changing the springs would leave the seat with a baggy, collapsed look. Also the non active seats have an across the seat metal link between springs, to stop you sinking between the springs. On active seats, this function is provided by the bladder assembly which is clipped to the springs, keeping their positions.

Wiring: the switch centre buttons for active seats just provide a signal to the active seat module, not a switched power supply, and the wiring is completely inadequate for all those fans. Forget the switch centre - its not codable, you can't add switches, nor move them around and is chosen to suit the cars equipment, which then determines if it is diagnosable or not. Since there is power to the seats, it would be easier and simpler to acquire the correct switch and fit into the blanked off position in the seat trim

Interesting, you seem to know much about these seats so i'm going to take advantage and ask questions...

1: replace bladders with sections of foam to provide support which you discussed above. this would keep the board in place and equate the volume of space which the bladders previously kept.

2: Understood that the centre switch provides signal to the module, which then powers the "comfort unit" would it not be possible to have the module power the fans in place of the bladder pump? (granted remove everything downstream of the module less the wires to power the fans) (I am also assuming the module output would be enough to power the fans, if this is not so then your suggestion of adding a switch to the seat and tapping into the power already there would be the way to do it....I am just looking to utilize the switches provided...)

3: thirdly, as I understand it, he active comfort system uses air (correct me if I am mistaken) so what would be and issue to substitute the bladders with several sections of tubing spread throughout the seat? (the ends of which would be facing up towards the top of the seat)

**chrisn7** · 02-10-2016, 08:04 AM

Originally Posted by Lamer321

I think it would all depend on the type of seat heating pad you had in the seat....if you wanted to keep the seat heater in the first place....This is what I discussed in another thread, but no one has replied yet...

Trimming the heating element pad? specifically around the heating wire itself? (...to make openings for potential ventilation fans to blow air through...) It would appear that the only benefit of that material is to keep the pad in place and reduce movement. I would imagine that some adhesive would suffice.

The cutting would be done throughout the entire heating pad and would be much more precise then what is detailed below but you get the idea....cut out the red areas to open up the passage of air...

it should be noted that I have the active comfort seats and would not have to deal with the "hills and valleys" of the sport seats and may be easier to manage.

a second note should be that the active seat bladders would be removed (maybe), and I would utilize the wiring harness to power the fans. and as a result have stock switches on the console to operate the fans

a third note would obviously be that I would need to have perforated leather swapped into the seats in order for this whole plan to be effective.

finally a fourth note would be that I intend to do this to both the front and rear seats, all the while maintaining the heated option (depending on the type of heating pad that the seats have)

I am very interested to hear opinions and thoughts on this as I live in Houston the idea of vents far outweighs the idea of heated seats...

You are looking at the drivers seat heating there. Do not expect the passenger side to be the same. It may well have a 'floating' element that is not part of the seat cover, but the entire element floats between the cover and the foam, being attached to the foam in just 2 places.

The seat builders seem to have ensured that the spec was met, but you can find one non-active seat with active seat wiring, the other without. Similarly, you might find a heating element on a non heated seat. Seen both anomalies

**Lamer321** · 02-10-2016, 08:09 AM

Originally Posted by chrisn7

You are looking at the drivers seat heating there. Do not expect the passenger side to be the same. It may well have a 'floating' element that is not part of the seat cover, but the entire element floats between the cover and the foam, being attached to the foam in just 2 places.

The seat builders seem to have ensured that the spec was met, but you can find one non-active seat with active seat wiring, the other without. Similarly, you might find a heating element on a non heated seat. Seen both anomalies

that picture was just used as an example, (not my actual seat) I wanted to use the heating element as an example due to the location of the heating wire...

and one more question: the active comfort bladder system uses air? (correct me if I am mistaken) But what would be and issue to substitute the bladders with several sections of tubing spread throughout the seat? (the ends of which would be facing up towards the top of the seat)

**Liam79** · 02-10-2016, 10:05 AM

Hi folks. Just popping in E38 land from E39 land. Why have I not done this before?! Now this is my kind of thread!

Although I bought an E39 I almost bought an E38 and am in the process of fitting as many E38 bits and pieces in my E39 as possible, including Contour seats which I'll be adding active to also. I've also looked into the cooling option a bit too. I have collected some pics of how the E65 seats are constructed which I can post up later when I'm home if they will be useful for you guys.

Basically I think the downstream side of the fans in the foam is doable. You go through the heat element, but as above should be able to punch holes in it avoiding the wires. I've seen two constructions of the upholstery - one has a thin white heat element on which you can easily see the black wires, that is immediately under the leather, then padding beneath (about twice as thick in comfort seats compared to sport seats). Another construction is integrated heat element and padding that is thick and grey and you cant see the wires. I think that's an older construction (possibly very old E38 only).

You have to go through the padding also - on E38/E39 that is a pretty tight cotton wool-like padding. Not optimal to blow air through. The E65 ventilated seats seem to use a different type of padding with a very open structure allowing air to flow around evenly under the leather and come through all the perforations - not just directly over the fans.

Then of course the leather needs to be perforated. I'd be surprised if the retrofit perforated covers are available from BMW but not sure. Otherwise a trip to an upholsterer.

Upstream of the fans I'm less sure as I haven't been able to find any pics of how the E65 seats are constructed. The problem I see is the back of the fans are directly up against the lumbar bladders and active bladders/boards if you have those. Finding some way to duct input air past those from the side into the fans is perhaps the answer?

To answer some of your questions Lamer...

2. I believe upon sending the signal from the switch centre (via GM I think) to the active module, it will then expect an OK signal back from the active module if it is working or it will shut down (and maybe give an error code). Also the module has quite a specific control process running the pump to inflate one bladder, then pausing, then allowing that bladder to deflate, pause, inflate the other bladder, switching the valves as required. I think it would be hard to hijack the module output to run fans and give it's OK signal to the GM. But maybe doable if you could understand exactly what the active system is doing.

3. The active system actually uses a fluid (water glycol or something if I recall). But whether air or water, I think it would be difficult to tubing to give the same expansion as a bladder, but maybe not - worth looking into. Probably easier to just find a way to duct input air past them and retain them (and the lumbar bladders) stock.

**Lamer321** · 02-10-2016, 10:25 AM

Originally Posted by Liam79

Hi folks. Just popping in E38 land from E39 land. Why have I not done this before?! Now this is my kind of thread!

Although I bought an E39 I almost bought an E38 and am in the process of fitting as many E38 bits and pieces in my E39 as possible, including Contour seats which I'll be adding active to also. I've also looked into the cooling option a bit too. I have collected some pics of how the E65 seats are constructed which I can post up later when I'm home if they will be useful for you guys.

Basically I think the downstream side of the fans in the foam is doable. You go through the heat element, but as above should be able to punch holes in it avoiding the wires. I've seen two constructions of the upholstery - one has a thin white heat element on which you can easily see the black wires, that is immediately under the leather, then padding beneath (about twice as thick in comfort seats compared to sport seats). Another construction is integrated heat element and padding that is thick and grey and you cant see the wires. I think that's an older construction (possibly very old E38 only).

You have to go through the padding also - on E38/E39 that is a pretty tight cotton wool-like padding. Not optimal to blow air through. The E65 ventilated seats seem to use a different type of padding with a very open structure allowing air to flow around evenly under the leather and come through all the perforations - not just directly over the fans.

Then of course the leather needs to be perforated. I'd be surprised if the retrofit perforated covers are available from BMW but not sure. Otherwise a trip to an upholsterer.

Upstream of the fans I'm less sure as I haven't been able to find any pics of how the E65 seats are constructed. The problem I see is the back of the fans are directly up against the lumbar bladders and active bladders/boards if you have those. Finding some way to duct input air past those from the side into the fans is perhaps the answer?

To answer some of your questions Lamer...

2. I believe upon sending the signal from the switch centre (via GM I think) to the active module, it will then expect an OK signal back from the active module if it is working or it will shut down (and maybe give an error code). Also the module has quite a specific control process running the pump to inflate one bladder, then pausing, then allowing that bladder to deflate, pause, inflate the other bladder, switching the valves as required. I think it would be hard to hijack the module output to run fans and give it's OK signal to the GM. But maybe doable if you could understand exactly what the active system is doing.

3. The active system actually uses a fluid (water glycol or something if I recall). But whether air or water, I think it would be difficult to tubing to give the same expansion as a bladder, but maybe not - worth looking into. Probably easier to just find a way to duct input air past them and retain them (and the lumbar bladders) stock.

hmmm, that return signal could be an issue, and good point about ducting the air into the fans. there are numerous things to consider, but this would be one amazing feature to have. Ill try to look into the module functions and signals a bit more.

maybe best to remove module completely and hard wire the "ok" signal voltage back to the switch/computer. meanwhile using the switch to activate a STSP relay to allow power supply to the fans (hijacking said power from the seat position motor input power? seat heater power supply? comfort module power supply?.... or just running a new line from the battery, through a fuse, to the relay and directly to the fans.) obviously using the materials already under the seat would be best, but in name of innovation and ventilation this should be a breeze.

**Liam79** · 02-10-2016, 10:42 AM

A breeze ha ha awesome pun!

Personally I'm keeping active - in fact I haven't even got it yet so no way I'm going to all the effort of installing it in Contour seats to then remove it!

So I'll have to find some alternative for control signal (but how to make it look OEM arrghhh...).

One thought about using the active buttons though - even if it detects a fault and eventually shuts off, presumably the module's 'attempt' to startup the active system is some pulse of power to the pump or whatever. You could presumably hijack that to switch a latching relay that would turn the fans on. Plenty of power under the seat to run them. Another press of the active button would switch it off. So it would work but the indicator LED on the active button wouldn't stay on when the fans are on which isn't ideal.

**Lamer321** · 02-10-2016, 04:24 PM

Originally Posted by Liam79

A breeze ha ha awesome pun!

Personally I'm keeping active - in fact I haven't even got it yet so no way I'm going to all the effort of installing it in Contour seats to then remove it!

So I'll have to find some alternative for control signal (but how to make it look OEM arrghhh...).

One thought about using the active buttons though - even if it detects a fault and eventually shuts off, presumably the module's 'attempt' to startup the active system is some pulse of power to the pump or whatever. You could presumably hijack that to switch a latching relay that would turn the fans on. Plenty of power under the seat to run them. Another press of the active button would switch it off. So it would work but the indicator LED on the active button wouldn't stay on when the fans are on which isn't ideal.

hmmm good point, that could be a fall back if I cant find a way to bypass that "OK" signal. I would like the light to stay on as the indication of the fans actually running. Should be a fun little project.

I currently have heated front and rear seats and intend on testing this out with the rear seats first (as I don't often people haul) this would let me keep the seats out of the car for some time while I figure out how to ventilate past the heating element. Pending rear seat success the only other hurdle would be the comfort system switch for the front seats...

- - - Updated - - -

you will have to excuse my poor Microsoft word design skills but from my understanding this is what I will be dealing with inside the seat...particularly the top comfort push plate the the bladder pushes up on, and finding a way to duct the airflow into the fans, up through the airbag sensor (passenger only) through the seat heater and through the (eventually perforated) leather.

this is in the active comfort seats: correct me if I am wrong please.

Capture.JPG

**Liam79** · 02-10-2016, 05:49 PM

I found the old pics of E65 seats I had...

So actually I did find out how they get past the lumbar and active bladders - just forgot. And it's dead simple - they simply avoid them!

You can see in the first pic of a base cushion foam they just mount the four fans in front of the hard boards for the active bladders. On the backrest they just mount four fans above the lumbar bladders.

On the upholstry covering you can see the large holes punched through the padding and heater and I think there is in there somewhere a sort of 'distribution layer' of a 3D open structured material (last pic) that allows the air from the fans to spread to the whole area of the seat and exit through all the perforations. That last pic is from rear seats so I'm not 100% sure if that material is in the fronts but think it is (sure I did have a pic but maybe misremembering).

Best would be to get E65 upholstry in hand, which I guess these days probably isnt hugely expensive. If you have some sick haberdashery skills you could probably pick up a set of E65 foam and upholstry and unpluck all the fans, wiring and materials you need.

- - - Updated - - -

Here's the gumph about the actve seats. Even describes the feedback signal, so maybe possible to trick it and use the buttons to run your fans...

Function

Operating principle

Two liquid-filled plastic sachets (fluid bubbles) are integrated in the seat upholstery. These bubbles are uniformly filled when at rest. When the active seat is switched on, a pump is activated that empties one bubble and completely fills the other so that the seat surface is raised on one side. This status is maintained for approx. 10 seconds. The bubble is then emptied to the mid-position. After a renewed pause of approx. 10 seconds the bubble is completely emptied and the other bubble completely filled.
This process ensures that the pelvis is continuously tipped slightly resulting in movement of the lower spinal column. The muscles work permanently (as when walking) and do not suffer from fatigue. The body remains relaxed.
When at rest, both fluid bubbles are approx. 15 mm high. When the system is active, the height changes between 0 and 30 mm. Although the bubbles are incorporated under the seat upholstery no elevation in the seat surface can be noticed when the seat is not subject to load.
The active seat can be activated as from ignition lock position 1 (terminal R). After switching off, the pump continued to run until both bubbles are in the mid-position.
Push buttons

The push buttons for operating the active seats are integrated in the centre console switch centre.
The line to the control unit for the active seat is switched to low (ground) for 30 ms by pressing the corresponding push button in the switch centre of the centre console. The control unit activates the active seat and also switches the line to low (ground) for 30 ms. The function LED in the push button is then switched on.
Feedback does not take place and the function LED remains off if the line to the control unit for the active seat has a break or if there is a fault in the active seat.
No feedback is sent by the control unit when the active seat is switched off.
Pump unit

The pump unit contains the following components:

Fluid pump with DC motor
Pump with alternating direction of rotation for filling and emptying the fluid bubbles
Position transmitter (Hall-effect sensor)
The mid-position of the fluid bubbles is recognized by way of the position values.
Pressure switch
The pressure switch (one per bubble) switches off the pump when the pump begins to build up vacuum. The bubble is then completely empty.
Solenoid valve
The solenoid valve prevents the fluid flowing back

Fluid bubbles

The fluid bubbles are filled with a water-glysantin mixture. They are connected to the pump unit by means of plastic hoses. The pump unit and fluid bubbles must be replaced together in case of repairs.
Control units

Control units that control the pump unit are provided for the driver's and front passenger's seat. The control units are connected to the P-bus. The corresponding coding as to whether the control unit operates the driver's seat or the front passenger's seat takes place via Pin 5 (signal name COD) at the 6-pin plug connector of the control unit. The pin in the control unit on the front passenger's side is connected via a line to vehicle ground
The control unit for the driver's seat contains an acceleration sensor that registers the transverse acceleration of the vehicle. Operation of the active seat is temporarily interrupted at very high transverse acceleration levels.

**Lamer321** · 02-11-2016, 12:24 PM

Originally Posted by Liam79

I found the old pics of E65 seats I had...

this is what your pictures look like....
Capture.JPG

but good find, that is an interesting location for the fans. you would thin that you would want them on your lower back and closer to your bum for optimum cooling, im curious how effective they are in those locations. thanks for lookin out.

**Liam79** · 02-11-2016, 01:28 PM

Yeah not sure what's going on - the forum seems to be having problems loading my Imgur hosted pics the last two days. Dunno if it's the forum or Imgur but my pics seem to work on other forums???

I find if you right click, properties to get the image address (in IE) or right click, copy image address (chrome) then enter that in a new tab they work. Weird.

Hopefully you can see them!

- - - Updated - - -

Originally Posted by Lamer321

you would thin that you would want them on your lower back and closer to your bum for optimum cooling, im curious how effective they are in those locations. thanks for lookin out.

Well I thought that too - and I guess that's why they have this distribution layer of open structured material to allow the air to go everyhere instead of just blasting out directly above the fans. I've never tried the BMW ventilated seats, but have tried some in a new Kia something-or-other electric car and they work well with air coming out evenly when I always previously thought this feature must surely be a gimmick and you'd probably just sit on and block the perforations over the fans and never feel anything.

**Lamer321** · 02-11-2016, 02:59 PM

well I learned something about my computer today, it can "Inspect" the images you posted...SO I COULD SEE THEM! and they look great, that placement is perfect! especially with that 3D mesh stuff.

The only reason I would use the active comfort button would be if I had removed the active comfort system entirely (thus leaving the button free to function the fans) but from looking at your pictures (which I will post in the next reply for all to see) it seems very doable to add them around the active comfort system.. and as Chrisn7 stated earlier, put an era appropriate switch in the blanked out space on the sat trim...

awesome pictures, helped a lot. but a few more questions:

in the third picture though, is that the standard seat heating element?

and can you just cut through any part of it or were those holes strategically placed to avoid the heating coil? (I cannot make out any pattern of heating coil in that pad)

- - - Updated - - -

Originally Posted by Liam79

I found the old pics of E65 seats I had...

So actually I did find out how they get past the lumbar and active bladders - just forgot. And it's dead simple - they simply avoid them!

You can see in the first pic of a base cushion foam they just mount the four fans in front of the hard boards for the active bladders. On the backrest they just mount four fans above the lumbar bladders.

On the upholstry covering you can see the large holes punched through the padding and heater and I think there is in there somewhere a sort of 'distribution layer' of a 3D open structured material (last pic) that allows the air from the fans to spread to the whole area of the seat and exit through all the perforations. That last pic is from rear seats so I'm not 100% sure if that material is in the fronts but think it is (sure I did have a pic but maybe misremembering).

Best would be to get E65 upholstry in hand, which I guess these days probably isnt hugely expensive. If you have some sick haberdashery skills you could probably pick up a set of E65 foam and upholstry and unpluck all the fans, wiring and materials you need.

- - - Updated - - -

Here's the gumph about the actve seats. Even describes the feedback signal, so maybe possible to trick it and use the buttons to run your fans...

hopefully the pictures are now visible...