Headlight vacuum switch

[William2]

On my S4 USA spec Elan which I am converting to RHD I intend to stick to the fail safe headlight system with the single spring and vacuum reservoir. Unfortunately the parts that came with the car did not include the dash mounted vacuum operated switch so I will need to try and find one!! My immediate question is whether the switch is the same as that for the non fail safe system? I also intend to keep the system as simple as possible and not bother with any micro switches or headlamp flashers. Less to go wrong and easier to wire up!

[pharriso]

On my S4 USA spec Elan which I am converting to RHD I intend to stick to the fail safe headlight system with the single spring and vacuum reservoir. Unfortunately the parts that came with the car did not include the dash mounted vacuum operated switch so I will need to try and find one!! My immediate question is whether the switch is the same as that for the non fail safe system? I also intend to keep the system as simple as possible and not bother with any micro switches or headlamp flashers. Less to go wrong and easier to wire up!

The failsafe switch is different in that it has 2 micro switches attached that open/close the earth path from the light relays & switch the headlight relays. Do a search on "microswitch"

If you're not going to use the micro switch functions then either vacuum switch (fail safe or non-fail safe will do.).

The bad news is that both the "normal" vacuum switch & the failsafe vacuum switch are difficult to find. I think I have seen one of either on eBay in the last 2 years & they went for over a hundred pounds.

[billwill]

Fortunately my own one is OK, but pondering on the non-availability if it ever broke, I did consider that with a lathe you could make an equivalent one.

The centre in my 'design' would be a cylindrical hole, with 3 side holes with narrow pipes, glued or screwed in.
Front (nearest to knob) a feed from the vacuum reservoir in the front cross-member
Middle a feed to the headlight pod(s)
Back; a vent to atmosphere.

The centre would be a sliding plug with two O-rings near is ends, sealing to the cylindrical hole walls. It would have a longitudinal groove in the side of the plug (or just a narrower section) between the O-rings.

When pulled forward the groove would connect the middle feed to the front pipe and when pushed back it would connect the middle feed to the atmosphere vent.

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A difficult but not impossible task. It would look nice in brass, or a work of art in clear perspex.

[pharriso]

Or convert/adapt a Corvette switch as Greg Z did...