Ice engines were originally designed as direct replacements for ice cooled cars that began operating in the 1920's. They were used in many heavyweight cars. Pullman used ice cooling in sleeping cars and diners.

Two ice chests under the car could hold up to seven tons of ice in 200 or 300 pound blocks. All the windows had been double glazed with two sashes to provide better insulation. The ice was supported above the floor of the ice chests so water could collect underneath. This cooled water was pumped into heat exchangers that resembled auto radiators located over the passenger compartment. Electric fans blew cooled air into ducts to circulate it throughout the car.

Most Pullman cars originally had clerestory roofs. An arch roof built over the original roof contained the air cooling equipment. Each Pullman section had its own cooled air vent in both upper and lower berths. Thermostatic temperature control was very primitive. Frequently you needed an extra Pullman blanket to sleep at night.

Water returned from the heat exchangers went into sprinlers located over the ice blocks so it was cooled on its way down to the cold water sumps. As the ice melted surplus water was dumped onto the tracks.

Ice engines directly replaced the ice chests. Propane powered four-cylinder Waukesha engines provided mechanical cooling for water. Then this cold water (usually brine) was pumped into the existing air cooling equipment. No modifications were required. Other variations replaced the heat exchangers with Freon evaporators. These did not require draining water out to prevent freezing damage in cold weather. Some long haul train runs required both heating and cooling of passenger cars during the trip.