I have a 1998 GMC suburban. There are controls for the front and for the rear. First the fan part went up in the front so my husband replaced the blower motor. Now the air is coming out up front again but it won't get hot. No heat up front only. The fan and heat are working in the back. Can someone please give me advice I can pass on to my husband. I appreciate it and thank you so much.

 

Probably the blend door actuator or a stuck blend door. They should be under the dash.