Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Load peak reduction
If the charge state of the battery does not improve, even after the idling speed has been increased, the peak load in the vehicle electrical system is reduced. The peak load reduction is achieved by the following actions:
- Pulsing the load with pulse width modulation (PWM) signals
In this process, consumers (e.g. the electric auxiliary heater) are switched on and off for defined times. To pulse the electric auxiliary heater, the power management outputs a PWM signal in the DME / DDE, depending on the energy available. The PWM signal contains the information for the maximum switch-on power available for the electric auxiliary heater. The frequency of the PWM signal is fixed at 160 Hertz (Hz).
- Power draw reduced to a certain percentage.
- Individual consumers are switched off in extreme situations when the power reduction achieved through pulsing and reduced consumption is insufficient.
The load on the vehicle electrical system is reduced according to the table:
| Priority of consumers | Power reduction | Control unit |
|---|---|---|
| Heated rear window | Pulsing | IHKA |
| Seat heating | level 2 | SM |
| Seat heating | 50 % | SM |
| Active seat | Off | SM |
| Heater blower | 75 % | IHKA |
| Steering wheel heating | Pulsing | SZL |
| Heater blower | 50 % | IHKA |
| Mirror heating | Off | TM from 09/2005: KGM |
| Heated rear window | Off | IHKA |
| Seat heating | Off | SM |
| Steering wheel heating | Off | SZL |
| Active seat ventilation | Off | SM |
| Heater blower | 25 % | IHKA |
NO RELATED
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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.