Lude Generation

when i switch the engine off after a drive no matter what the coolant temp is the cooling fan cuts in and runs for a few seconds but only when i turn the ignition off is this a lude thing secondly when i switch the rear screen heater on it creates interference with the radio i have cleaned and checked all the earths in and around the rear of the car only earth i havent found is for the rear screen itself just wondering if this gremlin could be part off my mystery brake light warning lamp issues also

Noise on the radio from the rear window demister being on is more likely to be poor earth on the Aerial wire sheild, or the stereo itself (rather than from the rear demister). But yes, could well be linked to the bulb warning. Earths in the boot area, or (I now think more likely) one of the various ones for the dash.

As for the fans running after turning off... yours is a ukdm, right? something is telling me some ukdms had an additional timer module that did run the fan for a while after shutting off the engine... Have a look in the service manual (or supplements) for fan timer module. It's located next to the engine ecu iirc...

just checked the prelude manual and yeah it does show a timer relay for the cooling fan , and it seems the demister earth is up under the rear of the headliner will look into this when i fit my high level brake light