How does the AUTOTHERM ERS system work?

When a vehicle is driven, only 40 to 60% of the energy available from the fuel is used to propel the vehicle.
The rest of the energy is lost as waste heat and transferred to the water surrounding the engine and dissipated to the outside air by the vehicle radiator.

In winter, this hot water is circulated by the engine pump to the cabin heater to keep the passenger compartment warm.

This engine coolant contains a large amount of latent energy that is available to the cabin heater as long as the engine pump keeps running and circulating it to the heater.

As soon as the engine is turned off, circulation stops and the heater begins to rapidly cool blowing cold air in a few minutes. Using a small magnetically coupled pump, the AUTOTHERM system continues circulation of hot engine coolant to the heater when the engine is off, operates the heater fan and effectively continues vehicle interior heating with the engine off.
This is thousands of times more energy efficient than idling.


I run overnight in a sleeper cab and stop to rest for 3 or 4 hours. Is the AUTOTHERM ERS system able to keep the sleeper warm?

The system is not designed for sleepers for 8 hours of rest.
There is not enough heat energy stored in the system to accomplish this.

However, sleepers with integral bunk heaters can be kept warm for approximately the same time as the cab, which might be sufficient for short rest stops of 3 or 4 hours.

A sleeper kit is available for this purpose and allows the driver to actuate the bunk heater fan.


Can I install the AUTOTHERM ERS system myself?

If you have experience working on and maintaining your own vehicle, changing fuses, engine oil, antifreeze and filters and can read pictorial drawings, yes.

There are only five vehicle connections to make. The rest are system connections.


How long does it take to install the system on a truck?

The average experienced mechanic will take 2½ to 3 hours to install the standard T-2500 AUTOTHERM ERS system, including one or two options.

Once he has made a couple of installations and is familiar with the particular vehicle and the installation requirements of the AUTOTHERM ERS system, he can cut this to under 2 hours.

Detailed and condensed instructions and a pictorial schematic makes subsequent installations easy.

Also, help is available from the factory. Just give us a call Monday thru Friday and we’re happy to help.


How much fuel can the AUTOTHERM ERS system save me?

I always thought diesel engines sipped fuel and needed to be idled because they’re so hard to start in the cold?

Small truck diesel can easily consume ¾ of a gallon of fuel in an hour at low idle.
A large class 8 truck engine can burn 1 to 1.2 gallons or more at high idle.

According to the U. S. Dept. of energy, idling each winter costs the long-distance trucking industry a per-truck average approaching $5000 per winter for fuel, maintenance and decreased vehicle service life. Multiply this by 400,000 to 500,000 L. D. trucks and the money wasted in idling each winter becomes substantial.

A well-maintained diesel engine with winter fuel or fuel additive is not difficult to start.

And a warmed diesel is not difficult to restart.

The AUTOTHERM ERS systems never cool engine coolant down to ambient (outside) temperatures. Operation terminates when coolant temperature drops to around 95° F. T
he rest of the engine coolant cool-down takes place at the same rate as any shut-off engine. In extremely cold weather, ether starters help cold engine starting.


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.


Why do you call AUTOTHERM ERS a system?

Because AUTOTHERM ERS systems are integrated into the vehicle’s electrical, heating and engine systems to operate automatically in cold weather each time the engine is turned off.

No buttons to push or adjustments to make.

The heater continues to run at the same comfort level as when the engine was running.

A seasonal on/off switch turns the system on at the beginning of the heating season and off at the end. An automatic version even turns the system on and off between seasons.

A nice feature for truckers traveling between warm and cold areas of the country.

A central control unit monitors all functions and operations, automatically turning the system on when the engine is turned off and terminating operation when engine coolant temperatures drop below comfort levels.


Do I need my ignition key to run the AUTOTHERM ERS system?

No, you do not need the key in the ignition.

Leaving the ignition key in the on or accessory positions will prevent the system from functioning.

AUTOTHERM ERS systems work only when the engine is off.

The vehicle can be left safely locked with the system running.

The driver can return to a warm interior hours later without the need to clear snow or ice since it usually melts as it falls on a warm surface.


How long will AUTOTHERM ERS systems keep a stationary truck warm?

Heating time is influenced by four main factors listed in diminishing order of influence:

  • size of engine (coolant capacity),
  • outdoor temperature,
  • wind and sun.

The main factors are coolant capacity and temperature:

  • A typical V-8 equipped car will stay warm (72° F inside temperature) for an 1¼ hour to 1½ hour when the outside temperature is at freezing.
  • A large class 7 or 8 truck with 50 to 60 quarts of coolant will stay warm for considerably longer approaching 3-4 hours.


Why is the AUTOTHERM ERS system called an energy recovery system?

Because the systems take waste energy from another process (combustion to propel a vehicle) which would normally be lost (dissipated to the outside air) and recovers it for a useful purpose (to heat the passenger compartment).

At the same time AUTOTHERM ERS systems are energy conservation systems as well because they reduce fuel consumption by eliminating the need to idle in order to keep vehicle interiors warm in winter.