Tom, you figure this out yet? I have the same sound....seems to be getting worse (more often) No matter how I adjust the controls on the A/C, I can't make it start or stop the tapping. (Wife's rear air on her Expedition is making same sound but it's the temp control actuator...can make it stop by slowly moving the temp knob 3 clicks from coldest setting)ok, so when I'm driving sometimes (seems more at night or in the dark with lights on ect) my truck makes this loud ticking, tack tack tack tack tack kinda sound lol. I got my wife to record it last night in the dark not sure but I think it's electrical and A/C or fan related and like a very loud relay or something? anyway here's the clip it's not for vid just to hear the sound.
VIDEO0079.mp4 video by hawaiianbasshead - Photobucket
lmk what you guys think...
Some how my 10 year old daughter can touch the dash and say "Please stop" and it does...EVERYTIME.. craziest thing ever. lol