Inline brake light switch operating pressure

[Andrew1967]

Anyone know what hydraulic pressure should operate the inline brake light switch ?

Have some originals to test and they don't appear to work using standard airline pressure.

[Spider]

I don't have data on the original switches to hand, but the Hella Hydraulic equivalent has a make range of 3 - 6 bar (45 - 90 PSI), so it is possible that you may be falling short on pressure using air.

[Andrew1967]

Thanks Chris

I think you could be correct regarding too low air pressure

We have some hydraulic pressure testing/setting equipment at work, so armed with this information I can have another go tomorrow.

[Polarsilver]

That is interesting if a normal Brake Light Switch has an operating pressure of say 90psi as Spider tells us .. & with 1071Bob establishing a S rear subframe Brake Limit Valve when under testbed conditions dead ended a wheel cylinder at 450psi .. can it be that reproduction Brake Light Switches tend to fail in early use because they cannot stand the potential maximum applied brake system pressure .. OK perhaps it is past my bedtime

[Spider]

That is interesting if a normal Brake Light Switch has an operating pressure of say 90psi as Spider tells us .. & with 1071Bob establishing a S rear subframe Brake Limit Valve when under testbed conditions dead ended a wheel cylinder at 450psi .. can it be that reproduction Brake Light Switches tend to fail in early use because they cannot stand the potential maximum applied brake system pressure .. OK perhaps it is past my bedtime

It's fairly common on most stopping applications in most cars to 'make' in excess of 1200 PSI. I'm not sure what the working, proof and burst ratings are of these components, but considering this, it's surprising how relatively cheap these parts are and that items, like these Hyd Switches, with crimped tops don't shoot off, though it's also partly why the tubing etc has such a small bore.

It also makes a bit of a mockery of residual pressure valves set at 4 and 10 PSI.