This is an old thread but it turned up on my search for "heater control valve".
I found this post intriguing because I am also throwing code 92 EVAP capillary leak, .5mm detected. Aside from the code, I'm noticing a regular tapping sound which occurs every 8-12 seconds or so. I have narrowed down the sound as coming from my heater control valve (attached to left front strut housing just below/beside the MAF sensor and intake boot).
It hasn't started getting cold yet around here so I have not had a chance to test the heating ability of the system --a symptom noted in other posts.
So, my question is: is my heater control valve bad or is it more likely that related hoses are cracked/leaking? or is it indicative of other problems?
As a side note, possibly related, my coolant reservoir bleeder screw has broken resulting in some fluid leaking. I've just ordered all the parts for a cooling system overhaul. Anyone think this will stop the heater valve from tapping?