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Fig 1: Electrical Heater With Timer Function Communication Diagram

Courtesy of VOLVO CARS OF NORTH AMERICA.

The desired departure time is set using the steering wheel module (SWM) (3/254).

The central electronic module (CEM) (4/56) calculates when the heater needs to start. The heater starts 2 hours and 45 minutes before the set departure time, irrespective of the temperature. A text message is displayed in the driver information module (DIM) (5/1) when the electrical heater is running.

The accessory electronic module (AEM) (4/78) electrically controls when the heater should be switched on and off. The engine block heater must be connected to a wall socket. The accessory electronic module (AEM) activates a relay which closes the switch for a heater element.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Electrical heater with timer function

Use the Manual With the Right Hardware

When to See a Mechanic