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Anyone figured out how to use the ST3 seat heaters after a recaro swap w a base seat?

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Location
st Louis
#1
I’ve had ST3 recaros for about a year and love them but getting the heated seats working would be spectacular. Anyone done it or know how I could?


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OP
ruscarus
Messages
17
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1
Location
st Louis
Thread Starter #4
I almost ordered one but wasn’t clear how to make the adjustment, or if there is one needed, for the ST3 focus recaros


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Messages
43
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10
Location
Fairfield County
#5
Oh you have the Focus ST3s. Best bet would be to try and find the heat pads and swap them out. The FoST recaros have multiple settings, not just on/off.
 


Krug

Active member
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MI
#6
I'll chime in since I have some second-hand knowledge of the Focus Recaro heaters and assisted a customer with getting my harness to work with them with some success.

If I recall, the multiple heat settings of the Focus seats are managed by modules attached to the seats themselves. The Fiesta seats have a single level controlled by the BCM. Theoretically it is possible to bypass this module completely and connect the retrofit harness to the heater elements directly. This would allow the Focus seat heaters to operate just as the Fiesta seat heaters would since they'd now be functionally identical.

The trick here is to identify the heater wires (should be two per pad, so four wires per seat), disconnect them from any other circuit, splice them together in parallel (which should give you a total resistance that falls within 2.2ohm to 3.3ohm) and then connect those leads to the retrofit harness as you would the Fiesta Recaro seats.

Unfortunately I no longer have a copy of the Focus seat wiring diagrams, so someone else will need to supply that.
 


OP
ruscarus
Messages
17
Likes
1
Location
st Louis
Thread Starter #7
I'll chime in since I have some second-hand knowledge of the Focus Recaro heaters and assisted a customer with getting my harness to work with them with some success.

If I recall, the multiple heat settings of the Focus seats are managed by modules attached to the seats themselves. The Fiesta seats have a single level controlled by the BCM. Theoretically it is possible to bypass this module completely and connect the retrofit harness to the heater elements directly. This would allow the Focus seat heaters to operate just as the Fiesta seat heaters would since they'd now be functionally identical.

The trick here is to identify the heater wires (should be two per pad, so four wires per seat), disconnect them from any other circuit, splice them together in parallel (which should give you a total resistance that falls within 2.2ohm to 3.3ohm) and then connect those leads to the retrofit harness as you would the Fiesta Recaro seats.

Unfortunately I no longer have a copy of the Focus seat wiring diagrams, so someone else will need to supply that.
@Krug could I adjust your wiring harness to a 3 temp switch? any more wiring harnesses that I could start from or are you all sold out?


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Krug

Active member
Messages
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460
Location
MI
#8
@Krug could I adjust your wiring harness to a 3 temp switch? any more wiring harnesses that I could start from or are you all sold out?


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I'm all sold out and have no plans to produce more, sorry. I've made plans and required materials available here on the forum. I'd have it linked in my sig, but for whatever reason I cannot add links to my sig anymore.

As for implementing a "3 temp switch," I'm gonna need more information about how you plan for this to operate before I can tell you yes or no. Offhand, I would say no, or at least "not well," because the harness I devised replicates the factory wiring and operation, and therefore all heater functions are actually controlled by the BCM which tries to hold a set heat level by cycling power to the heaters on and off based on what I believe is a timer function.

Basically, if you wanted the harness as I designed it to allow multiple levels, you would have to somehow program that into the BCM and alter the factory switch telltales to signal which heat level is enabled (in other words, not realistically possible). Else, you could put the level switch in-line of the heater power wires but this would require you to first hit the factory heater button, then set your level with another switch, and would furthermore have the drawback of only receiving intermittent power due to the BCM timer function. This could definitely work, but I cannot guarantee how well it will work in practice. You would also need to find a location for these level switches.

If you were to use an eBay seat heater kit with multiple levels or similar, you'd be much better off not using my harness at all, using whatever harness it comes with to bypass the BCM entirely and just tap into a +12v lead in the passenger fusebox that is only hot when the ignition is on (this is important so that the heaters are not operating while the car is off, draining your battery. I cannot remember if the spot my harness taps into is ignition-hot or not, so verify that), and placing the control/level switch wherever you like. That's the easiest, and most trouble-free way to get multiple heat levels, but will require you to find a placement for the switches. I wanted to avoid this because I did not want to drill holes somewhere in my console or dash for the aftermarket switches and just wanted to replicate the factory operation as it was intended. It's up to you, of course.

Now, with the control modules in the Focus seats, I do not have direct hands-on testing experience with them so as far as I know there is NO way to get the built-in modules and switches to operate correctly with the Fiesta. I do not know if the seat modules communicate with the Focus BCM in any way or if they are purely independent and simply need power supplied to them. It might be possible, but it is not something that I have explored and I do not think I will ever have the chance to do so.
 


Last edited:
OP
ruscarus
Messages
17
Likes
1
Location
st Louis
Thread Starter #9
I'm all sold out and have no plans to produce more, sorry. I've made plans and required materials available here on the forum. I'd have it linked in my sig, but for whatever reason I cannot add links to my sig anymore.

As for implementing a "3 temp switch," I'm gonna need more information about how you plan for this to operate before I can tell you yes or no. Offhand, I would say no, or at least "not well," because the harness I devised replicates the factory wiring and operation, and therefore all heater functions are actually controlled by the BCM which tries to hold a set heat level by cycling power to the heaters on and off based on what I believe is a timer function.

Basically, if you wanted the harness as I designed it to allow multiple levels, you would have to somehow program that into the BCM and alter the factory switch telltales to signal which heat level is enabled (in other words, not realistically possible). Else, you could put the level switch in-line of the heater power wires but this would require you to first hit the factory heater button, then set your level with another switch, and would furthermore have the drawback of only receiving intermittent power due to the BCM timer function. This could definitely work, but I cannot guarantee how well it will work in practice. You would also need to find a location for these level switches.

If you were to use an eBay seat heater kit with multiple levels or similar, you'd be much better off not using my harness at all, using whatever harness it comes with to bypass the BCM entirely and just tap into a +12v lead in the passenger fusebox that is only hot when the ignition is on (this is important so that the heaters are not operating while the car is off, draining your battery. I cannot remember if the spot my harness taps into is ignition-hot or not, so verify that), and placing the control/level switch wherever you like. That's the easiest, and most trouble-free way to get multiple heat levels, but will require you to find a placement for the switches. I wanted to avoid this because I did not want to drill holes somewhere in my console or dash for the aftermarket switches and just wanted to replicate the factory operation as it was intended. It's up to you, of course.

Now, with the control modules in the Focus seats, I do not have direct hands-on testing experience with them so as far as I know there is NO way to get the built-in modules and switches to operate correctly with the Fiesta. I do not know if the seat modules communicate with the Focus BCM in any way or if they are purely independent and simply need power supplied to them. It might be possible, but it is not something that I have explored and I do not think I will ever have the chance to do so.
Thanks for all this info Krug!


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Krug

Active member
Messages
708
Likes
460
Location
MI
#10
Thanks for all this info Krug!


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No problem at all.

After contemplating it, I do believe that if you place a "level switch" inline of the power wires for the heaters, that alters the resistance in steps of like 0.3ohm per step, with the max setting having no added resistance, it could work. The caveats here are that this switch or whatever else is altering the resistance MUST be able to handle up to 100w without failing or bursting into flames, and that you be aware that after the initial switch-on period, the heaters will cycle on and off every few minutes per the BCM programming.

The heater power circuit is a very "dumb" circuit - the BCM simply gets a signal from the momentary switch on the center stack when pressed, and turns on the LED telltale in the switch and triggers the heater power relay to close the power circuit. It does not monitor the heater circuit resistance or anything like that. There's no actual "logic" besides the BCM timer cycling the relay on and off. When the relay is on, the heaters are basically connected straight to the +12v system in the car, so the peak heat output is determined by the resistance of the pads. (Power = Voltage^2 / Ohms)

Now, I would say that you might have better luck adding a 2-setting switch that can switch the way the pads are wired (parallel for high, series for low) but the output on the low setting might be too low. I'll explain.

Assume that the each of the two pads per seat (cushion and backrest) have resistances of 4.4ohm.

When in parallel (both pads "positive" leads wired together to power source, and both "negative" leads wired together to ground) the resistance is cut in half which results in 2.2ohm resistance and about 89w output at 14v for quick heat and a toasty butt on cold winter days.

When in series (first pad "positive" connected to power, its "negative" connected to the second pads "positive," and second pads "negative" connected to ground) the resistance is doubled, resulting in 8.8ohm resistance and about 22w output. I'm not sure that this would be sufficient.

Even if you were to devise a way to have each pad on its own circuit, the output would be ~44.5w (4.4ohm@14v) per pad, so total output per seat would be the same as the "high" setting. If the low setting had each pad on its own circuit it would also have to add another ohm or so to each pad circuit to keep total output around the 45w mark.

Anyways, good luck with whatever you decide to do.
 


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