Overview - Heater

There are different versions and manufacturers of the heater and A/C unit. Individual components of the different heater and A/C units are similar but not the same. Interchanging components from different manufacturers is not permitted.
The heater on a vehicle without an A/C system is the same as the heater and A/C unit on vehicles with a "Low" A/C system. The evaporator installed in the heater is without function, here it functions only as a place holder and to reduce noise.
The expansion valve -C- is installed on a vehicle without an A/C system only to seal the pass-through in the grommet to the vehicle interior.

Courtesy of AUDI OF AMERICA, LLC
The connections on the expansion valve (for the A/C system refrigerant lines) are connected on vehicles without an A/C system with a closure cap -A- (tightening specification of the nut -B- 8 Nm).
The layout and the removing and installing of the different components of the heater is the same as on a heater and A/C unit of a "Low" A/C system.
Removing and installing the heater is the same as on a "Low" A/C system heater and A/C unit. Naturally, the components that are only installed on the A/C system are omitted (emptying and filling the refrigerant circuit, removing and installing the refrigerant lines from the expansion valve).