Help please? Have an 07 Titan, replaced VCB, BLOWER MOTOR. When I'm running air or heat on floor to defrost and switch to vents there is a knocking, varies from around 5 to 15 seconds, and when I turn engine off it will do same? Also when I turn fan on the relay next to blower clicks, that I understand, problem is when I turn all the way on high (last setting) same relay clicks again and blower motor quits till I turn diel back one notch! Any ideals that can help? Please and thanks!!