Mercedes-Benz W212 OM642 electrically controlled thermostat
Which thermostat fits the W212 OM642 engine?
The original electrically controlled thermostat has part number A6422002215 and opens at 92 °C. The version that opens at 87 degrees is the wrong model. A wrong or faulty thermostat keeps the engine too cool.
Why is the thermostat electrically controlled and what does the fault code for the heating element mean?
The engine control heats the thermostat's wax element with an electric resistor, so the thermostat opens faster. This allows engine temperature to be managed for fuel economy. The fault code for a wire break in the heating element does not turn on the engine warning light and does not affect anything else. A disconnected connector can cause the code.
How is the thermostat replaced on the OM642?
The coolant is drained from the radiator drain tap on the driver's side. The housing can be removed without extensive disassembly once the thin fuel hose is released from its holder. The lowest bolt can be awkward and may come out with the thermostat.