Aftermarket Heated Seats

[narkotic]

Hi - I want to swap my factory leather seats (with heat) for aftermarket seats (with heat). I imagine the aftermarket ones are less complicated, but I could not find much here regarding this topic.

I want to integrate the factory heated buttons to these new seats. Is it as simple as locating the wire and connecting, or is it some overly complicated CAN-controlled system and I need some sort of aftermarket module (or build one via ESP32)?

Controlling levels 1,2,3 are hopefully as simple as different voltage outputs. But in the BMW world everything is overly complicated. The german way. thanks.

[smokinjoe64]

Originally Posted by narkotic

Hi - I want to swap my factory leather seats (with heat) for aftermarket seats (with heat). I imagine the aftermarket ones are less complicated, but I could not find much here regarding this topic.

I want to integrate the factory heated buttons to these new seats. Is it as simple as locating the wire and connecting, or is it some overly complicated CAN-controlled system and I need some sort of aftermarket module (or build one via ESP32)?

Controlling levels 1,2,3 are hopefully as simple as different voltage outputs. But in the BMW world everything is overly complicated. The german way. thanks.

Generally, replacing OE to AM seats is fairly simple, "uncomplicated" for a DIY project. Did my Recaro install solo...toughest part was wrestling those heavy OE seats out
Coding is required to eliminate airbag related warnings.

All BMW electrical wiring for seat controls resides underneath each seat; all plug-in to a simple harness [ie motors, seat belt sensor, airbag, heater]. Typically, no special tools required, yet depends on AM seat and features involved.

Keys to success include:

> Compatible AM selections - Seat wiring/harness, mounting assy etc.; especially for motorized seat replacements
> Time & Patience

Post threads and YT vids exist to give a sense of topic...

[narkotic]

Yea - I appreciate all of that but I am already aware as I found tons of topics on the whole airbag thing and how to code stuff.

I'm asking how to integrate aftermarket heated seats to a BMW heated seat interface. Do the wires that ultimately go to the OE seat simply supply different voltage to the coils, or is it more complicated. Like, do I need to keep a box behind, or can I find the pins and just connect them to give me low/med/hi .

[smokinjoe64]

Originally Posted by narkotic

Yea - I appreciate all of that but I am already aware as I found tons of topics on the whole airbag thing and how to code stuff.

I'm asking how to integrate aftermarket heated seats to a BMW heated seat interface. Do the wires that ultimately go to the OE seat simply supply different voltage to the coils, or is it more complicated. Like, do I need to keep a box behind, or can I find the pins and just connect them to give me low/med/hi

Depends on your choice of how this function to work and AM seat config.

> Model intended to install?
> Already 'compatible' ready for BMW harness?

There are options for how-to methods along with different config requirements.
For instance, Recaro CS use simple 12V heating circuits (2-stage or 3-stage depending on model/variant).
Typical options:

1. OEM-style (retain BMW buttons & functionality)
2. Standalone Recaro heating
3. Hybrid (OEM buttons => aftermarket controller)

Easiest method for use of OE buttons, load handling, w/o CAN headaches:

• Use BMW heater output to trigger relays
• Power Recaro heaters from fused 12V
• Keep OEM control working
  > Friends example, retained OE wiring harness from donor seat. Build custom adapter harness (don’t cut car wiring).

All said, precisely why didn't opt to carry over heated seats to Recaro's.
IMO, too much hassle - - additional direct cost increase of seats; required mods/customization efforts...living in SoCal who 'needs heat'

[narkotic]

Ok, I figured it out.

If you have fully loaded seats equippied (airbag, motorized, heated) you will have a big ECU under the seat A187 (Driver side) with a ton of plugs going in and out of it.

Reading the diagrams in ISTA, you only need connector X733 (seat pad / heat sensor), X732 (rear pad) and X13709 (input from car / yellow plug). The rest are for motors, airbag stuff, etc. With the connectors facing you, it goes X13617 / X733 (3 pin) / X732 (2 pin) / X13709 (5 pin)

I connected X13709 to the car (Power / CAN) and X733 to the seat pad and a 10k ohm thermistor, and X732 to the rear pad. Polarity doesn't matter. The pads are driven via PWM.

The thermistor connects to pin 3 on X733. You can opt to just leave it there which isn't safe, or you can stuff it in the seat where it will actually monitor the temps and shut down the system if it gets too hot. Your call.



Hope this helps someone in the future retrofitting a generic seat heating pad (two wire).

[narkotic]

Update : sensor is also there for closed loop monitoring and temperature control / regulation of the pads. Without it inserted, the system eventually gets really hot and then due to no feedback shuts down. Takes a few minutes.. I'll have to either insert them into the seats somehow, or just use a fixed resistor around 7-8k ohm to trick the system into thinking they are warm.

[smokinjoe64]

Originally Posted by narkotic

Ok, I figured it out.

If you have fully loaded seats equippied (airbag, motorized, heated) you will have a big ECU under the seat A187 (Driver side) with a ton of plugs going in and out of it.

Reading the diagrams in ISTA, you only need connector X733 (seat pad / heat sensor), X732 (rear pad) and X13709 (input from car / yellow plug). The rest are for motors, airbag stuff, etc. With the connectors facing you, it goes X13617 / X733 (3 pin) / X732 (2 pin) / X13709 (5 pin)

I connected X13709 to the car (Power / CAN) and X733 to the seat pad and a 10k ohm thermistor, and X732 to the rear pad. Polarity doesn't matter. The pads are driven via PWM.

The thermistor connects to pin 3 on X733. You can opt to just leave it there which isn't safe, or you can stuff it in the seat where it will actually monitor the temps and shut down the system if it gets too hot. Your call.

Hope this helps someone in the future retrofitting a generic seat heating pad (two wire).

Originally Posted by narkotic

Update : sensor is also there for closed loop monitoring and temperature control / regulation of the pads. Without it inserted, the system eventually gets really hot and then due to no feedback shuts down. Takes a few minutes.. I'll have to either insert them into the seats somehow, or just use a fixed resistor around 7-8k ohm to trick the system into thinking they are warm.

Nice job sorting challenge...sounds like a favorable outcome
If plausible, any supporting pics, clips illustrating above 'notes' certainly helpful for DIYers.

[narkotic]

[narkotic]

Ok, now they really work. I found some larger format NTC thermistors (same value) and un-hooked the fabric from the seat in the front and stuffed them in under the front of the pad (did it all by feel). They now measure down in resistance when the pad is on and the car likes it.

[smokinjoe64]

Originally Posted by narkotic

Ok, now they really work. I found some larger format NTC thermistors (same value) and un-hooked the fabric from the seat in the front and stuffed them in under the front of the pad (did it all by feel). They now measure down in resistance when the pad is on and the car likes it.

Sweet
When you have the chance...what's the all-in tally for parts/componets, et all used to retrofit?

[narkotic]

The parts are cheap. It's the labor and the knowledge research that isn't. I'm an EE so these things come easy to me.

So - to answer your question, parts-wise, $10? Not including the seats of course with the heating pads installed.

But having to figure out how it works, take the seat apart, install it, that is 5-8 hours right there. At my rates, that is $1,500. Hope that helps.