Seat Heat/Cool Ventilation Blowers

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2008 GMC Yukon XL, 2008 GMC Yukon, 2008 Chevrolet Tahoe, 2008 Chevrolet Suburban, and 2008 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

The ventilation blowers are self contained electronic air conditioners consisting of a blower motor with an inlet air filter, thermal electric device (TED), temperature sensor, and waste air duct. The air flow from the blower is divided into 2 streams and directed across both sides of the TED, one side into vent passages through the seat foam and the other out the waste air duct. While the system is operating in either the heat or cool modes both heated and cooled air is generated as it passes across the TED. When voltage is applied to a TED, one side releases energy as heat, while the opposite side absorbs energy and gets cold. Heat or cool modes are determined by the polarity of the supply voltage to the TEDs. The climate control seat modules (CCSM)s rely on inputs from temperature sensors located in the ventilation blowers near the TEDs to control seat temperatures. The thermistors are 2 wire sensors supplied with a 5-volt referenced signal circuit and a low reference circuit from the CCSM. Resistance through the thermistors varies with temperature causing the heated seat sensor signal circuit voltage levels to decrease as the TED temperatures rise. The CCSM monitors the temperature of the air flow into the seat foam and continuously adjusts the blower speed and TED temperature by regulating the current flow through each component.