[GMcL]

As Simmy suggests, low battery voltage will throw codes left right and centre, not just Volvo cars.

Condensation, looks like there may be two issues. 1. Water ingress 2. Aircon compressor.
The compressor in my car stopped working resulting in water running down the inside of the windscreen though I didn't have any wet floor carpet. The system held charge but not blow cold air. Simple test to see if it is working is put a thermometer in one of the dashboard vents and put it on its coldest setting (with the engine running) should be below 8°C at the vent after a few minutes.
Get the carpet dried out and put cat litter in a Tupperware container to absorb the moisture in the car. Cat litter is great for soaking up liquid spills or condensation. Put a sticker/postit note on the steering wheel reminding you to take out or put the lid on the container before you drive off.