Honda have issued a Product Update for All MY* 2011 Civic models FN1,FN4, FK1,FK2 & FK3 MY* Model Year, This prodcut update in under TSB #SO-02-002-00 dated 30-06-14. The Symptoms The performance of the cabin heater is poor and the customer may notice a difference in outlet temperature from left to right sides. The Cause The heater core was blocked with contamination which led to poor heater performance. The contamination was caused by a faulty water softener within the factory, which supplied the coolant filling machine with water contaminated with chloride. This results in a level of internal surface corrosion developing in the cooling system. The resulting corrosion blocks the heater core. Countermeasure at factory (Swindon) A reverse Osmosis unit has been fitted after the water softener process. In addition, conductivity sensors have been fitted which will detect a rise in chloride and shut off the water supply should equipment failure occur. Application to Production Line SHHFK1***BU012397 Europe SHHFK2***BU013381 Europe SHHFK3***BU003402 Europe SHHFK3***BU100220 South Africa SHHFN1***BU001421 Europe SHHFN4***BU003672 Europe For affected vehicles please contact your nearest Honda dealer. The Repair method. First Remove Remove the thermostat cover and check for corrosion (see pic). Then thoroughly flush the entire system of this contaminated coolant the procedure is quite detailed and elaborate.