Escort radiator fan

Hello together, drive an Escort Cabrio 1.6 Zetec, from 1998 with air conditioning and have the following problem. If the air conditioning is switched off, the fan will only start when the temp. display is on “L” (from NORMAL) – quite loud, apparently level 2. If the air conditioning is on, the fan will start already when the display is on “M” – quieter and slower, level 1?!? Accordingly, the voltage is always high when you stand in the traffic jam – the fan jumps on, or now the temp goes into the red With my model there is no temperature sensor on the large hose on the cooler. The following things I have already checked / exchanged: Fan resistance on the fan Ventilator Aror Relay (behind the battery) Thermostat cooler ventilated fuses in both fuse boxes are OK. Thought also on the Temp-feeler, but if it was defective – the system would not start the fan even if the climate was switched on. I have no idea what it might be, much more Someone else has an idea from you. Thank you.