[xcession]

I bought a used (1yo) TCDi last month and love the car, however this morning encountered something weird and suspect it may be connected to another 'glitch' which is less worrying.

The thing this morning was: after driving the 20miles to work with the heaters on (it was 1oC), discovered that after turning off the ignition, the cooling fan did not turn off and instead got faster and higher pitched.

I turned the ignition back on, the fan subsided, then after a second or two kicked in again. Turning the ignition off, and the fan got even louder, as before.

I eventually turned on the ignition, pressed some of the a/c circular ventilation buttons several times, then turned off the ignition, and it finally shut down properly.

Related to this (maybe) is the fact that despite having never used the A/C since I bought the car, I find that when I turn on some of the other heating features, the A/C turns itself on! Some days i can just start the ignition and the A/C turns itself on.

These things definitely seem related - A/C that seems to be on by default, and fans that don't know when they're supposed to be on or off.

The car is still within warranty, but I'd just like to pick your collective brains before I take it in. Is there a known fault I can point the Ford mechanics to directly? I don't want to risk the mechanics not-finding the problem and charging me.

[Hometune]

I am not familiar with a Focus as new as yours because it is so new.
Most cars will run the cooling fans after shut down if the engine coolant temp is above a preset limit. This is normal and is to prevent damage caused by hot spots. Your car will probably have 2 fans or at least a 2 stage fan so this would account for the additional noise.
On most new cars, if you select window demist/defrost on the heater controls, the aircon automatically comes on and the fan runs at full speed. This is because the aircon has a drying effect and clears the screen faster. I would never use the 'recirculation' button as this causes a build up of moisture inside the car and misted up windows. It is recommended to use the aircon in winter and summer to keep the parts and system at its best so aim to switch it on say, once a week for at least 20 mins.
If you are still not happy, take it in under warranty. You will not be charged. Maybe ask them to demonstrate the best way to use this system in your car if you are not familiar with it.

[xcession]

Thats really helpful, thanks. Yeah the A/C comes on when i press recirculate, but I think it also came on when i'd turned on the ignition from cold and simply had the fans directed to the windscreen and recirculate off. Are you saying thats normal too?

With the explanation you've given that would certainly make sense. I guess i'm just a little miffed at how uneconomical it is to run A/C at the same time as everything else. I'd prefer to have to enable it myself than have the car make that decision for me!

Regarding the fans being on after ignition-off, what was so worrying was how loud it was and how long it lasted. It was loud enough to hear inside the office. I went inside, made a coffee at quite a leisurely speed, came out again and it was still on. It was a couple minutes later (having turned the car on/off several times) that it eventually turned off.

It was below freezing outside when I got to the office and although i'd had the heating in the car on the entire journey it still seems rather surprising that the car needed that long to cool down, particularly given the ambient temp.

If you're saying these things are normal then thats fine. My last car was an 02 and I know things have advanced quite a way since then. Part of my problem is working out what is a bug and what is intentional new-fangled tech :P

[Hometune]

As I say, if you are passing the dealership, just ask them for advice. If there is a fault, with the trade being very quiet, they will be all too happy to get some work into the workshop under warranty.