Dashboard illumination (PWM or voltage?)

[Alex \(YMG\)]

Hi,

Could anyone tell me if Volvo Trucks use PWM instead of voltage regulation
to control the dimming of the dashboard illumination?

My reason for asking is that I have a radio unit (Volvo VR200) fitted to my
240. Supplying varying voltage to the 'illumination terminal' of the radio
results in odd behaviour which leads me to believe the radio may use PWM
dimming?

Thanks

Alex