Trying to install my new hands free kit with the autoleads stereo mute adapter. Trouble is can't work out whether I have a "car radio mute" lead on my 1998 vintage head unit. I've worked out all the wires bar one. If its not this then I haven't got one.

Its a white cable coming out of the head unit on its own and its officially labelled "DOOR SWITCH"

What the **** does that mean??? Its measuring a positive voltage, does this tie in with a CRM lead?

If it isn't for that purpose then what else is it for??

Please help Autoleads technical won't answer!!!
Cheers
Ritchie.

 

Its for I belive its built in alarm that squeeks via the speakers when the door is open - connect via the door pin switch or interior light.