There were a handful of cool suit system failures in the NASCAR Cup race at the Circuit of the Americas and while many might want to place the blame on faulty hardware the root cause is actually a bit more complex and often due to team choices for performance.
A cool suit system typically consists of a small box that is a miniaturized air conditioning unit which has an input and output for a hose that runs over the chiller. Those hoses are connected to hoses which are coiled on a shirt that the driver wears under their firesuit. When the system is functioning correctly fluid circulates through the cool suit unit and is chilled before getting to the hoses on the shirt. The ambient heat in the car and the body heat of the driver will warm the liquid as it moves through the coils in the shirt but it will still cool the driver down and be chilled again once it circulates back through the unit.
