HELP! What is this button for?

[NigelC]

I was pulling out my dash (1979 GTV) to get a roll-cage fitted and noticed an, after-market button under the dash on the right hand side, it's marked sportsroof release.  It's just a simple push-button with a two-way joint each with a hose attached, actually I'm not sure it was attached to the hose because one end of the joint had come undone when I noticed.

One hose goes to the sunroof (up the 'A'-pillar) where it does precisely nothing, and the other goes to the brake servo as pictured. 

I can't begin to think what it is for and what happend if I disconnect it.

[Sheldon McIntosh]

Passenger ejector seat?

[NigelC]

More info ...

Between the servo and the button was a distributor check valve or vacuum check valve.  I have no idea what this does or why it's in my car.

[Storm_X]

do you have a picture of the other end of the hose ?

[alfagtv152]

Hi Nigel,
I have not seen anything like it myself but from what you have shown it would be to vacuum operate the sun roof,some sort of auto open or close would be my guess.If you disconnect it make sure you plug the end at the brake booster,ie blank off the T joint so you do not lose vacuum.
Cheers
Andrew

[NigelC]

No I havent but I think I've worked it out.  The sunroof (an aftermarket rust attractor) originally had a 'lock' that could only be operated when the engine was running, so the roof remained secure when the car was turned off.  The button under the dash effectively provided air pressure to the lock when you pushed the button.  

The pressure was regulated through a distributor valve which I think works a bit like those showers that are designed to restrict the flow of water to just below that required for a decent shower!

I've disconnected it all now (the lock was not there when I bought the car), and sealed off the 't'-junction near the brake servo.  I'll get the hose replaced with one that doesn't have a 't'-junction.

[NigelC]

Andrew, I think you're right.

Thank you all for your help - especially the passenger ejection *thinks* 'very useful'.

[VeeSix]

Where does the other end go?