[shorod]

My wife's car was blowing very hot air (115 degrees F at the vents) on any setting other than 60 degrees F. At 60 degrees F (automatic), the air was cold.

The DCCV works in both directions. Well, I'm not sure that makes sense. The valve modulates the flow of coolant through the heater cores. If one or both of the valves is stuck closed, you will have very minimal (if any) coolant flowing through the heater corresponding heater core. However, if it is stuck open, you will have continuous flow through the core. I'm not sure how the modulation works, if it is a PWM square wave, or if it is a variable voltage that controls the flow. I suspect PWM. If that's the case, it makes a lot of sense how my wife's DCCV was failing. The sticking valve would work for zero% duty cycle (spring to hold it closed, as well as for 100% duty cycle. However, for fast switching in between, the valves would stick in the open position. It was obvious that at least one of the valves was rubbing the solenoid assembly.

So, in your situation, I'd say it could still be a faulty DCCV (due to the over-temp coolant when the engine overheated) or a coincidental wiring issue.

-Rod