Head Lights on 76 Elite S1

[The Nut]

Hi to all,

Lennie carry's on with surprises, have spent the last six weeks or so fixing electrical bugs. I think I've got them all sorted and now one of the head lights only comes up half way. When I turn the lights off there is a hiss from the vacuum tank and the light raises to its correct height, it does it on both flash and using the light switch with the ignition on and off.

 

Any ideas, does any one have details on how the vacuum system works.

 

Regards to all John