If there are any leaks into the vehicle from outside, the carpets should be wet and since it smells, it should be a rather bad eak. Since you are not able to find anything under the carpets, the only other place water can accumulate within the vehicle would be the A/C evaporator housing.

There is a drain hose at the firewall for draining the evaporator condensaton water. Ensure it is not clogged.

Answered by KHLow2008 (expert)
39,963 answers provided

All carpers are dry we have taken it to the garage who have treated the ac with a anti bacteria treatment but two days later the smell is still present.

Where snouts is the evaporator compartment on a Audi a3 57 plate

Response from mwsparks
1 question asked

It is at the lowest point of the evaporator housing. you should be able to feel it from under the dash.

Answered by KHLow2008 (expert)
39,963 answers provided

Is it easily accessible from drivers side or passenger side ?

Thank you for the help with five it a go tomorrow

Response from mwsparks
1 question asked

Passenger side would be easier as it is towards the center but accessibility is not too easy as space is rather tight. Getting at it from under vehicle would be easier.

Answered by KHLow2008 (expert)
39,963 answers provided