WARNING: This page is about a different car, the 2004 Volvo S40, 2003 Volvo S40, 2002 Volvo S40, 2001 Volvo S40, and 2000 Volvo S40. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Measuring The Resistance
Courtesy of VOLVO CARS OF NORTH AMERICA.
Measure the resistance:
switch open: ∞ Ω
switch pushed in: 0 Ω
.
Check when the key is pushed in the ignition that the bracket is moved inside ignition column.