CliveCh

Hi, wondering if anyone can help. I have a Skoda Octavia TDi DSG estate with the Climatic control system. Whilst travelling to work the other day I noticed that the fans had stopped working and also I was only getting hot air regardless of temp setting. After doing some googling and dropping onto this forum I have followed all the advice I can find to solve the problem, but have so far failed. Here are my findings so far: Have removed the fan and speed controller unit and serviced this with new capacitors and checked relay operation (I am an electronics engineer by trade BTW). This did not help, so I tried to figure out how the controller is working. It’s just a PWM controlled FET that chops up the DC to vary the output by way of varying mark/space ratio but I can’t understand how the vehicle/system is controlling it. I had it on my bench and put a bulb on the output and supplied it with 12v and there is no current draw, the internal relay needs to be bought in though before anything can happen and there are only two other connections on the controller plug other than 12v and Gnd. No matter how I connected them I could not get life from the thing. So I looked at the vehicle end to see if I could see how it works. There is the main supply cables then two smaller ones blue/white and black/white, both are at 0v level and no matter what I do with the fan speed control nothing changes on these terminals between either themselves of with respect to Gnd or 12v. So I can’t even decide if the controller is at fault or not. Have come across the “flaps reset” procedure, performed that, and at this point I realised the flaps aren’t moving either!! So the plot thickens. I assume you should be able to hear them calibrating and then stop after a few seconds but nothing at all. Can anyone give me a hint given all of the above what the issue might be so I can move forward? This is driving me nuts. I don’t know if this could be related but at roughly the same time I noticed my oil level/temp sensor had fallen out and was dragging on the floor 😟 but no lights on dash or any adverse effects to speak of, unsure if it could be connected though. Thanks in advance to anyone with any nuggets of wisdom.