Weird electrical issues - CCM, X Relay or Ignition switch

[Justinos]

The girlfriends 2005 Fabia has thrown up some weird electrical issues in the past week.

First off the heater blower stopped working, but at the same time we noticed the electric windows and rear wash wipe stop working. The front wipers, headlights were working fine. Also none of the interior lights work, but they haven't done so for quite some time, but could be related to the more recent issues.

I have checked all fuses, but given multiple circuits, suspected it wasn't this simple.

On carrying out further research I have learnt about the X contact relief relay, so will replace that this evening to see if it cures the issue. However I am beginning to have my doubts, as if it was the relay, then the front wipers shouldn't work by my reckoning, so am beginning to wonder if it is the CCM or a poor connection as that controls multiple different circuits, and could also explain the interior light issue. I have also got an ignition switch, but again think it can't be that as that is further back in the circuit, ie if that was faulty I would have more issues.

Is my logic correct, I have nothing to lose fitting the relay, but starts to get costly if it is the CCM?

Advice appreciated.

[Crasher]

You can't replace the connivance [sic] unit without having a diagnostic system so firstly you need to see what fault codes are stored on the central convenience and on board supply control unit as your faults involve a mixture of the two units.

[Justinos]

Thanks Crasher,

I ran VCDS last night. It didn't throw much up - suggested fuse for internal lights was faulty - but it is fine, and the flap for the recirc on the blower couldn't adapt. I will check the printout when I return later to see if it got any data back from the CCM and on board supply, but now assuming the relay isn't going to be my fix all?

My main priority is to get the heater working, so maybe the relay should help that?

[Justinos]

Fitted the relay and the heater, windows and rear heated window and rear wiper all working again. Interior light no different, but I am relieved the major problem sorted.