Shop manual says it's behind the dash...and you have to take it out to remove the heater unit...ouch!

Removal
1. Disconnect the battery ground cable.
2. Drain the engine coolant.
3. Discharge and recover refrigerant (with air
conditioning).
 Refer to Refrigerant Recovery in this section.
4. Remove the Instrument panel assembly.
 Refer to Instrument Panel Assembly in Body and
Accessories section.
5. Remove instrument panel center bracket.
6. Remove blower unit.
7. Remove evaporator assembly.
 Refer to Evaporator Assembly in this section.
8. Remove driver lap vent duct.
9. Remove Center & Lower vent duct.
10. Remove heater unit assembly.
 Disconnect heater hoses at heater unit.