Unrecognised noise from behind dash

[DAvid PLUME]

Have 1987 911 supersport ...... When i turn the ignition on i can hear what seems like a fan whirring from the dashboard ... but neither the fan or heater are switched on.... only had the car for a couple of months but dont remember hearing it before ... any ideas

[softinthehead]

no idea, except to say that all my 944/968s have done same. i like to think of it as my happy little car humming softly with contentment

but then I am much of the time

[richardlw]

fuel pump getting a bit noisy?

[DAvid plume]

THANKS VERY MUCH ...DOESNT SOUND SO BAD

[softinthehead]

THAT WHIRRING SOUND MUST BE GETTING VERY LOUD COS WE CANT HEAR YOU PROPERLY

[dilbert]

There's a small vacuum pump behind the dash. It sucks air into the small oval hole in the round "dummy button". The temperature of the air is measured and works with the dial by the handbrake to get the cabin temperature correct. The vacuum runs even if the heating isnt.