Seems awful strange that my heater core springs a leak, I bypass it, and a day later, my A/C evaporator kicks the bucket. I drove the truck Thursday, put the A/C on, and it blew warm. I popped the hood, and noticed the A/C compressor cycling on for only a second or two before turning itself off (no pressure will cycle an A/C compressor off to save it).

Off to the local shop. They verify low freon, so they fill it, along with the dye, and determine it's the evaporator that's leaking.

They performed an A/C compressor and dryer replacement for me a month ago, and informed me that one of the connectors from the dryer line to the evaporator had been cross threaded/stripped in a prior replacement (I did agree with them, as I knew some previous work done to the A/C caused the dryer to be replaced once before, and whomever did that, kinked one of the dryer lines and cross threaded the dryer fitting to the evaporator line.). They were able to use the old evaporator and get it to thread onto the new dryer, and told me they were trying to save me the cost of having to replace the evaporator due to this cross threaded issue. However, now that the evaporater failed one month later, the dryer had to be replaced again so that this issue of previous cross threading of the fitting would not mess up the dryer or evaporator. That dryer was only one month old.

Could a leaking heater core damage an evaporator , or is this just a dumb luck situation that both failed within a day or two of each other?

 

Just bad luck.

High humidity would be the only result of a heater core leak inside, and overheating engine outside.
Neither would effect evaporator.