Checking the combustion air flow

• Check for free air flow through the heater (that the air intake and exhaust are not blocked).

  Remedy as necessary.

other information: 

• For cars manufactured up to w38 2001 inclusive, see Engine coolant heater, replacing
• For cars manufactured from w39 2001 inclusive, see Engine coolant heater, replacing .

Was a fault detected? 

• YES 

  Refer to Verification 

• NO 

  Refer to Checking the flame sensor