heater noise on 2003 Mercury Mountaineer

no noise on cold. turn to heat and turn it up and the noise begins. this is my daughter's car in North Carolina.

Get Your Car Fixed at a RepairPal Certified Shop.
We certify shops based on expertise, quality work, and verified customer reviews
1 answer
You'll need to have someone look at this, or try to locate the source of the noise, without hearing it we simply cannot give much useful advice.