I hear a loud ticking sound from the dash of my 2002 Galant when the temperature control knob is on cold?

I hear a loud ticking sound from the dash of my 2002 Galant when the temperature control knob is on cold?
The sound goes off when I turn the temperature knob to warm. The noise only comes on when the ignition is on or the engine is running. Thank you. I pulled off the entire lower dash and used a stethoscope to locate the sound. I had to replace the heater valve motor assembly. That little item costs $140. ans is sold by the dealer only.