Here is a nice one. Homeowner calls and says he has water dripping out of his horizontal unit under his house, but says he hasn't had his A/C on in two months... And why does it smell putrid? Finally determined through the phone conversation that his drain is connected to the........SEWER!
Needless to say, we found this after the determined homeowner cut the drain line. The homeowner said it shot all over him as he was fumbling around for the pvc cap:
Note the lime he spread around as recommended by a plumber.
Here is the supply plenum after it was cut loose from the furnace. Obvious that it had been leaking for some time. The homeowner is away from home a lot, so these things run unchecked.
We ended up swapping out the system to a new 16 SEER two speed, after re-locating the furnace/coils to a vertical location more practical for service and access. We also installed a new drain line, terminating it at a different location... Outside where it belongs.
Our guys got well acquainted with tyvec suits, and masks for several days. It was a disgusting job to say the least.
The plumber arrived and found what caused the problem. A squirrel had gotten lodged in the sewer line via vent stack, and plugged it up. Lots of gagging and dry heaves to go around this job.