touran cooling issues

[Will UK]

Hi there. weird things happening with my Touran tdi. radiator fan kicks in at full speed once engine temp reaches 90, and goes off when i turn the engine off. recently replaced cts and stat with genuine parts but it didnt solve it. temp needle stays bang on 90 on the dashboard. today ive plugged my laptop and had a look at the engine coolant temp after 30 mins drive, and noticed that coolant temp starts to drop down when the engine idle, is it normal for it to drop to 80C, temp gauge on the dash stays on 90C.

vcds scan results are-

01415 - Recirculating Pump (V55)
010 - Open or Short to Plus

01411 - Temperature Sensor (G18)
007 - Short to Ground - Intermittent

01409 - Repeated Flame-Out
000 - - - Intermittent

but these are found in aux heater module, so any ideas how to solve radiator fan problem?

thanks