Headlamp Vacuum Tubes

[William2]

On an S4 Elan can anyone confirm to me which way round the 2 vacuum tubes connect to the dash vacuum switch on the angled connecting tubes (i.e. inner and outer)?

[nmauduit]

Ray's online manual shows how it is on my 1968 s4se (two pod version) :

http://www.rdent.com/manuals/elan/body/bl.htm

[Grizzly]

It's easy to work out, if you put some pipe on the in/out on the vacuum switch then suck each of them (with the headlight knob pushed in) one will be blocked off (that goes to the engine) the other will vent to the atmosphere (that goes to the headlight pods)

When you pull the switch out the two pipes should be connected (headlight up)

It's easier to explain that way because the vac switch assembly can be spun round in the dash hole.

[billwill]

The pragmatic engineers method:

One way it will work, the other way it won't.

The thinking engineers approach:

In one position the pods are connected to the vacuum source, in the other position the pods are connected to the atmosphere, therefore there must be a third 'hole' (which does not need a tube) and the pipe connecting to the pods must be the one in the middle of the other two holes.