A/C Micro-Switch
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 1984 Volvo 245, 1984 Volvo 244, 1984 Volvo 242, 1983 Volvo 245, and 1983 Volvo 244. However, it is still accessible from the selected car via links, so may be relevant.
Turn ignition off. Connect an ohmmeter between ground and terminal 16. Turn knob on air conditioning control panel. Resistance should decrease.