I noticed recently my S1 occasionally getting hotter than usual and realised that my cooling fans weren’t on when the temp is above the point they usually kick in. Other times they are working just fine. I’m assuming a faulty temp sender but has anyone else had similar?
You should plug in an OBD reader and see what temperature the ECU is reading (brown sensor), and then compare it with the dash (blue sensor). It may be that one of the sensors isn’t reading properly - I had this with the stack sensor recently, which made it look like the fan wasn’t coming on, but it was just really the blue sensor over-reading.
If you haven’t already, unplug the brown sensor cable and check the fan starts, to prove that side of it too.
Ah, intermittent problems are the worst to pinpoint! Next time you think that it doesn’t kick in, go straight to the brown sensor and unplug it. If it kicks in then you know it’s an instrumentation issue.
Do you know what temperature you expect the fans to kick in at too? It depends on what ECU you have (177/190/Emerald etc) too.
Sounds similar to what I experienced; nothing wrong with the cooling system and instead just the blue sensor (Stack) reading rubbish. The dash actually has nothing to do with the cooling system, other than being a diverse source of instrumentation. The standard fan cut-in is 104C, or 92 C if the 190 ecu is fitted, but you have to read this input temperature through the OBD.
Since replacing my blue sensor and properly grounding the Stack at the rear, dash temperature is not only rock solid but 3C colder with no electrical load!
The only way I know to check the ECU is the fan cut-in!
I cut the stack earth near the plug behind the stack unit, and the connected it to the stack to the rear earth point using a new cable, which is run up the centre console and through the bulkhead connector.