We don't have aircon, and I noticed a rotten egg smell, and it was the windscreen washer bottle had gone bad. Have a good sniff...:augie
A mixture of different brands I guess.
I emptied it, flushed it, then added some bleach solution, pumped it through, left it a few hours, but I also washed the vehicle in case the bleach affected the paintwork.
Drained the bottle flushed through with clean water, then added new screen washer.
Problem solved.:thumb2