1. Disconnect the wire from the "–" terminal of the battery.
2. Drain the coolant from the engine cooling system with the heater valve fully open (see "Replacing the coolant").
3. Remove the instrument panel (see "Removal and installation the instrument panel").
4. Loosen the clamps and disconnect both hoses from the heater tap pipes from inside the passenger compartment under the instrument panel (see "Removal and installation the heater radiator").
[The article is copied from the website vazbook]
5. Loosen the clamps and disconnect both hoses from the heater tap pipes in the engine compartment.
6. Unscrew the two nuts securing the heater tap.
7. Remove the heater tap from the front shield.
8. Remove the heater tap rod holder.
9. Disconnect the rod from the heater valve lever.
10. Remove the internal ventilation ducts by disconnecting them from the heater body.
11. Disconnect the wires from the heater motor.
12. Disconnect the wiring harness from the heater resistor.
13. Unscrew the two fastening nuts on the right…
14. ...and the left side of the heater (the ground wire of the heater fan motor is secured under the lower left nut), then remove the heater with the control panel.
15. Install the heater in the reverse order of removal.