[jedwards]

Hi all,
I am new to this forum but not entirely new to Astons. I had a DBS some 20 years ago, but have recently returned to the fold with the purchase of the gorgeous vehicle pictured below (sorry, image uplaod not workling currently)

I am hoping someone can help me, as I cannot resolve the constant hissing from the vacuum switches that control the ventilation/heater. The hissing seems to be coming from the individual switches, even though they all now work.
Can these be replaced and if so from where, and possibly what other vehicles may have used those same vacuum switch devices?
Many thanks

Jeff
In sunny Western Australia