1996 jeep cherokee.

Heater fan works only on high and squeals loud.
Left it parked all last summer and then it would work on high and squeal plus it would blow chunks of leaves and fuzz and smell like dead mice.

Here is what I did to fix it. Maybe this will help someone else out.

First,
From under the hood I pulled out the fan and vacuumed out the chipmunk nest inside. Fan bearings were shot so I replaced the fan with a used one I had here.
Result: No more debris and no more squeal
Problem: Still only worked on high and smelled bad.

Second,
Ran the ac on "max" and sprayed lysol spray in short blasts into the intake on the passenger floor.
Pulled the radio and the heater control from the dash and found the connector for the fan switch was melted. Replaced the connector with female spade connectors.
Result: Smells good
Problem: Still only worked on high

Lastly,
Changed the blower motor resistor with a new one from NAPA for $20
Result: Everything works as designed.

No more squealing, smelly, only running wide open, throwing chunks of stuff at you heat.