The “cool” function uses a fan, heat does not. Neither use the HVAC blower.
Both use a fan but for the heat function the fan comes on for a few seconds and doesn't stay on for very long but for the cool it stays on the entire time. I've had heated/cooled seats for 10 years and this is how they work. No one said anything about the HVAC blower. The fans are built into the seats.
Also found this technical explanation:
The seats use Peltier/Thermoelectric Plates. So it blows both hot and cold air. There is a module in the seat bottom and one in the seat back. They basically consist of a fan that blows over a Peltier plate. The plate can become hot or cold depending on the polarity. That's the simple explanation anyway.
And another:
These seats, like all Ford / Lincoln heated cooled seats, use a "TED" (Thermo-electric device) to generate the heat and the cold.
These devices generate heat on with polarity on one side, and remove heat with polarity on the opposite side. Pressing the cool button simply switches the polarity on the device.
A fan moves air across the heat sink of the device in both cases and blows this air through ducting up through the perforations on both the seat backrest and base. There may be 2 TEDs in each seat, we haven't determined that fully with this model yet.
The TEDs are more effective at heating than cooling, plus hot air rises. The fan will operate, but at a very low speed (so as not to cool the TED) but still move the air to the perforations.
Cooling uses more airflow to try and be effective.
The heated seat fans sometimes turn up and then down to control temp.
