Thermostat "weakening" and letting the engine run cooler than it should is a very common thing with the FIRE engine. Lots of posts on the forum about it. Every Panda we've owned has needed at least one changed during our period of ownership. Becky, our newest Panda, was running cool when we bought her.
Ours is a 2010 1.2 Dynamic Eco with the older 60hp FIRE engine and I replaced ours last year with one from Shop4parts. Be careful when ordering because the later FIRE engines (65hp with VVT cam sprocket, so around late 2011 early 2012 onwards) included the heater hose takeoff spigot and water temp sensor whereas the earlier engine is a much simpler, and cheaper, casting. S4p sell both the genuine FCA item and their "Original Birth" after market branded one. Don't be put off by the "Original Birth" brand name, I've had quite a number of their products and all have been of good quality. On the older 60hp engine the FCA one is more expensive and you have to buy the gasket separately - an extra fiver - whereas the Original Birth is cheaper and has a gasket included in the box at no extra cost. For me the original Birth is a "no brainer"! Doesn't seem to be any great price difference on the one for the 65hp engine though.
S4p's website, whilst generally very accurate, can sometimes be just slightly misleading and the thermostat for our 2010 1.2 Dynamic Eco is one of them. The site shows "Panda 111 (09 to 12)" and when you look that up you get this:
https://www.shop4parts.co.uk/?name=store&op=Product&ProdID=18857 which is the item for the later 65hp engine used from late 2011 onwards - you can clearly see the heater pipe spigot and water temp sensor which, on the earlier engine, are located on the cylinder head. Knowing that the 60hp engine was used in the earlier vehicles I looked up under "Panda 11 (04 to 09) and got this:
https://www.shop4parts.co.uk/?name=store&op=Product&ProdID=470 which is the one I needed. It's rare to find an "anomaly" like this but if you do decide to buy from them and you're in any doubt about a part's suitability do give them a ring, you'll find them very helpful.
