Cooled seats not cooling

[GT Pony]

Does anyone know how the peltier is cooled?

https://en.wikipedia.org/wiki/Thermoelectric_cooling

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[GT Pony]

Maybe that is the foam Free Agent is stalking about?

It looks like that foam piece is what separates the hot side from the cool side of the Peltier unit. I can see the cutout now where the hot air probably exits out of the hot side. I don't think I'd be messing with the thin Styrofoam piece.

http://www.mustang6g.com/forums/attachment.php?attachmentid=31721&d=1434251073

 

[Droid_Junky]

It looks like that foam piece is what separates the hot side from the cool side of the Peltier unit. I can see the cutout now where the hot air probably exits out of the hot side. I don't think I'd be messing with the thin Styrofoam piece.

http://www.mustang6g.com/forums/attachment.php?attachmentid=31721&d=1434251073

It seems that there is more air flowing over the heat sink side when it is set to cool. If that air flow was actually over the cool side I suspect we would have cooler seats. Maybe the lower unit is dispersing the air more evenly between both plates?

 

[Crais]

https://en.wikipedia.org/wiki/Thermoelectric_cooling

I think you misunderstood my question. :doh:

The hot side of any TEC, especially a peltier (which cannot sink remotely without a cooling apparatus) needs to do something with the heat. You certainly don't want it just to sink to the surrounding air because you end with a large net increase in temperature and a ruined device.

If there is a peltier for the seat, cooling it would need some way to keep the hot side cool other than just powering off when it overheats. Varying the voltage and PWM are both not appropriate for controlling a peltier, which would lead me to Ford using a simple On/Off (thermostat) circuit.

 

[GT Pony]

^^^ Look at the wiring diagrams in Post #145. There is obviously some kind of electrically powered cooling unit inside these units and a fan. My guess is the heat is blown out or just convected out. The units in the bottom section of the seat work fine ... the ones in the back don't and it very well could be because they can not reject the heat generated during cooling.

 

[GT Pony]

Here's my stab on what I think is going on. In the photo below, the red arrows show the rejected heat, the blue arrows show the cooled air that goes up inside the rubber duct after the fan blows it across the cold side of the Peltier unit and out the back of the seat perforations. The warm spot you feel on the back of the seat is being warmed up by the warm air rising out of the hot side of the Peltier unit.

The yellow arrow shows the thin Styrofoam insulation wall that separates the cold side from the hot side of the Peltier unit. The hot air just rises up and out of the hot side via natural convection, as the red arrows would be pointing in the upward direction based on how the unit is mounted in the seat back.

 

[Crais]

I'm missing what you're referring to.

Those schematics show a heater, variable resistor, what appears to be a motor relay or controller, and the motor.

The variable resistor is likely a RTD.

No sign of a peltier or an associated cooler.

 

[GT Pony]

I'm missing what you're referring to.

Those schematics show a heater, variable resistor, what appears to be a motor relay or controller, and the motor.

The variable resistor is likely a RTD.

No sign of a peltier or an associated cooler.

I believe what you think is a variable resistor is a temperature sensor ... probably for temperature control of the cold side. Look at the labeling of that circuit on the control module. Plus, Droid_Junky said the dealer plugged in a diagnostic computer and could read the temperature of the unit ... probably was measuring that very temperature sensor.

The Peltier unit is that thing in the schematic that looks like a little grill ... there is no heater in these units. The heated seat operation is not part of these units, it's a totally different mechanism to heat the seats.

 

[Crais]

Exhausting the heat from the very inefficient peltier cooling into the cabin would be a terrible design decision. That's not even touching on the tendency of the cold side of a peltier plate to condensate with even the slightest humidity. I don't see Ford doing this.

The heatsink is more likely to provide a sink for the (probably marginal)heat from the motor and/or SCME circuitry to prevent it heating up the air being pushed through the seat.

I could very well be wrong and I haven't looked beyond the photos posted here. If I can manage I'll take a look into my car tomorrow.

 

[GT Pony]

Exhausting the heat from the very inefficient peltier cooling into the cabin would be a terrible design decision. That's not even touching on the tendency of the cold side of a peltier plate to condensate with even the slightest humidity. I don't see Ford doing this.

And probably the very reason the units in the seat back don't want to cool down. Yes, I believe Ford can do this ... because I think we've proven they did do this. :doh:

The heatsink is more likely to provide a sink for the (probably marginal)heat from the motor and/or SCME circuitry to prevent it heating up the air being pushed through the seat.

I think that heat sink is indeed the hot side of the Peltier unit - it has to reject heat someplace. Any heat that the very low power fan motor produces is carried away by the ambient intake air by the fan, and cooled by the Peltier unit before it exhausts out the seat perforations.

 

[Crais]

I believe what you think is a variable resistor is a temperature sensor ... probably for temperature control of the cold side. Look at the labeling of that circuit on the control module. Plus, Droid_Junky said the dealer plugged in a diagnostic computer and could read the temperature of the unit ... probably was measuring that very temperature sensor.

The Peltier unit is that thing in the schematic that looks like a little grill ... there is no heater in these units. The heated seat operation is not part of these units, it's a totally different mechanism to heat the seats.

I read schematics as part of my job and unless the originator of those schematics isn't following standards that is a resistive heater element.

RTD = resistance temperature detector

EDIT: Apologies, I didn't realize that symbol can be a bit ambiguous. The function is the same but the method isn't always specific (i.e. still a heater, may not be the resistance sort).

 

[GT Pony]

I read schematics as part of my job and unless the originator of those schematics isn't following standards that is a resistive heater element.

RTD = resistance temperature detector

Are mixing terms? "resistive heater element" ... "resistance temperature detector". Isn't the RTD basically a "temperature sensor" like I said?

Now why would there be a resistive heater element inside a device that is supposed to cool?

 

[Crais]

Sorry, I was all over the place in that post.

It appears to me that the diagram is for the entirety of the climate controlled seats. When heat is engaged, the air is actively heated. When cool is engaged, the air is "not hot." However, cool doesn't mean actively cooled, merely circulated to provide a cooling effect.
The squared line (the grill looking thing) is the heater element used for heating the air when the heated seats are engaged. It could very well be that it heats the seat's surface and doesn't use the blower. The principle is still the same.

The variable resistor is likely an RTD, exactly what you said.

 

[GT Pony]

^^^ I tested my heated seats tonight while out on an evening drive. The whole seat surface heats up, both bottom and back - they work quite well actually. I think someone else mentioned that the heaters in these seats is more like and electric blanket design (ie, heating elements running all along the seating surfaces, bottom and back).

I think the little "grill" figure in the wiring diagram is indeed representing the Peltier unit. Note that in the wiring diagram in Post #145, they show a box around "blower motor" (label they use), and the number of wires in the schematic match the number of wires going into the fan/cooling unit. So everything inside that box in the schematic is what's inside the fan/cooler assembly you see in the photos posted in this thread. So the little "grill" figure do-hickey is inside the fan/cooler unit.

There is probably a separate schematic for the heated portion of the seats.

 

[Crais]

I see what you're saying, now. The key could be the boxing in of the "grill" since I've never actually seen a peltier drawn as a symbol, perhaps they improvised.

You might be correct, but I still can't see Ford exhausting peltier heat into the cabin. That's a pretty significant amount of heat relative to the cooling provided.

I have a suspicion that we're missing something important somewhere. If I have some time tomorrow I'm going to begin dismantling and see what I find in there then report back.

I'm going to hit the sack before I convince myself I need to do it right now.

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