For all models except 2000 Touring and 1971 models, start by disconnecting the lead from the battery negative terminal. Move the heater control lever to its hottest position and drain the cooling system. Disconnect the heater return hose near the windscreen wiper motor at the rear of the engine compartment, followed by the heater inlet hose from the water valve located in the cavity at the engine compartment rear bulkhead. Inside the car, remove the center console, the trim panel covering the steering column, the trim panels below the fascia panel, and the steering column upper shroud. Pull the two knobs from the heater air distribution controls on the left-hand side of the steering column, then remove the control escutcheon panel by unscrewing two external screws and two inner knurled nuts. Remove the ashtray, pull the knob from the heater control lever, and take out the control escutcheon panel along with the inner control screws. Disconnect the heater electrical leads, unscrew and remove the two heater mounting nuts-one located within the glove compartment and the other on the rear of the engine bulkhead. Disconnect the demister hose to allow slight movement of the bracket at the base of the steering column when unbolted. Remove the narrow trim panel from beneath the glove compartment, disconnect the remaining demister hose, and lift out the heater assembly. For installation, reverse the removal steps while ensuring the cooling system is filled. For 2000 Touring and 1971 models, the operations are similar, but pay attention to the location of the mounting nuts and secure the earth lead below the left-hand nut. Ensure a new heater sealing gasket is used during installation, and return the foam rubber block to its original position.