Omg you have got a beauty there and with the blue seats !! I was only commenting the other day I haven’t seen the blue or red for years x sorry I get a bit geeky about the early ones having a yellow one myself w reg. I think that it is the coolant temperature sensor from what you say and I have to tell you that even though he hasn’t done many miles and therefore the engine should be sound ,providing the oil was always topped up ,unfortunately the main problem I have experienced is that the sensors and switches do fail basically because of age. Wether it’s because of plastic going brittle or electric failure my first instinct if something goes wrong would be to do with sensor or switch.. I am so glad you have found our site and I think we collectively will always be there to help you whatever the problem xx please keep in touch and let us know how it’s going