Vehicle components can often be modified during its production cycle as day to day problems emerge and need to be resolved by redesign. This is something that some parts suppliers are slow to recognise, while First Line prides itself at being right up to date with the latest developments. 

A prime example of this can be seen on multiple PSA applications, Citroën C3, C4, DS3, Peugeot 207, 208, 2008, 308, 3008, 508, 5008, RCZ, Partner, BMW MINI - 1.4i/1.6i 2006 onwards, where there are known issues caused by the specification of the thermostat and thermostat housing installed during their original production. This led to an increasing number of premature failures, with many owners complaining of overheating related problems and reporting symptoms such as an irregular temperature gauge, erratic engine running, radiator fan run-on or poor heater function. As a result, PSA has modified the design of the thermostat housing several times in an attempt to correct the issues. The modified versions have several enhancements including reinforced connections and a more robust structure to minimise the potential of warping or fracturing. The lower sensor has been moved to accommodate a new electronically operated thermostat, which replaces the wax version used in the original design.

Technicians need to be aware that these modifications have meant that there is a visual difference between the new and old designs. In particular, the references that have been re-specified include First Line part number FTK422. Originally this had a single 4-pin sensor on top of the housing, but this has been modified by changing it to two, 2-pin sensors, one remaining at the top and the second being moved to the lower side. As this original single sensor has been split into two, a new wiring harness is required, which is only available from the OE supplier.

The OE design of the housing was then modified again, this time necessitated by the replacement of the wax thermostat by a new electronically controlled version and to accommodate the change, the lower sensor was moved round to the back of the housing. Therefore, FTK422 was subsequently superseded to FTK454 following these modifications.

Other supersessions include FTK102 and FTK396, which have been superseded to FTK481 and FTK477 respectively. The housing for these two references already had the two, 2-pin sensors and therefore only underwent the thermostat modification and lower sensor relocation.

In order to follow best practice, First Line recommends that when replacing any of these thermostats/thermostat housings, it is advised that the engine ECU software is checked and re-programmed before any components are replaced to ensure it is set to reflect the latest version.