If the system runs such a long time, won’t this run the battery down?

Yes and no. The AUTOTHERM ERS system is powered from the vehicle battery. However, the pump takes about ¾ of an amp to pump 3 gallons a minute. Most of the power is used by the fan.

This varies from vehicle to vehicle from a low of 2-3 amps at low speed to 5-6 amps in older vehicles when set at the low/medium fan speed, which is the maximum needed to keep the interior warm.

The fan speed should run at the lowest speed that maintains comfort.

All AUTOTHERM ERS systems are equipped with a solid state battery voltage sensor that monitors battery voltage at all times and under all conditions of vehicle operation, engine off or on, ERS with system running or off.

If low battery voltage is encountered, a blinking red light warns of low battery voltage and turns the AUTOTHERM ERS system off if it is running. This leaves enough battery voltage to restart the engine.