I have a Carrier Central Air conditioner - 6 years old - and a Lennox gas furnace - 12 years old. The AC evaporator coil appears to be installed over the upflow furnace. About 3 weeks ago I found water on the floor beside the furnace. It appeared to be running down the outside of the furnace from the bottom of the evaporator coil. I called for AC service. The tech opened up the evaporator coil unit but could not find any leak, also we could not duplicate the problem by running the AC. He said it may have been due to the high humidity that day but I had been running it on other humid days with now problem.
Next day, the fan motor was making a whining sound and eventually cut out. The tech who came to look at that replaced the fan motor, said it was in bad shape, clogged with dust/dirt in spite of an electronic filter. He suggested that poor fan operation may have caused ice to build up in the AC and then leak.
Next day, the leak came back, but this time water was in the bottom of the furnace. Again, the tech could not figure out where it was leaking from. He checked all the hoses, checked the pump and the outflow which runs into the laundry tub. I had been collecting water there in a bucket and knew that the hoses, pump etc. were working. After that the AC ran fine, with no leaks for about 10 days. Today it is very hot here so I lowered the thermostat from 76F to 74F to cool the house. About an hour later, the leak started again, this time with water running down the side of the furnace, apparently from the evaporator coil.
I have to call in the tech again. Meanwhile, can anyone offer any suggestions as to what the problem might be?