Checking the intake air flow

• Remove the heater:
  • 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 .

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

  Remedy as necessary.

Was a fault detected? 

• YES 

  Refer to Verification 

• NO 

  Refer to Checking the flame sensor