'63 R1 Hydraulic brake switch

[DobbM]

Still waiting for my shop manual to arrive.

Thank you for any advice.

It takes the brake pedal to be pushed about 95% of full range to activate the brake lights. Aside from slamming on the brakes for an unexpected obstacle, I don't think I ever really have the pedal go that far. It appears to be a hydraulic switch on the master cylinder, so not adjustable. Correct? The fluid is full, and since a trusted mechanic replaced all the brake lines with stainless, I'm sure that they were bleed properly. Also, the brake booster was rebuilt, and a new master cylinder installed. The brakes themselves work fine, and no squishiness, etc.

A). Should I try and bleed the lines first to help diagnose (or if I need to replace the switch, I'll have to bleed them again).

B). Do the switches fail? Or should I be looking elsewhere for my perceived issue?

C). If they do fail, where might I start hunting for a new one?

[Gunslinger]

You have "DOT 5" on your master cylinder cap so I assume that's what's in it.  Silicone brake fluid is notoriously difficult to bleed all the air out of...the little air bubbles like to hide wherever they can and defy being bled out.  If the car had standard DOT 3/4 fluid in it and wasn't completely flushed out and all the hoses replaced you will have spongy brakes or even fail in rare cases.  The best performance cars don't use DOT 5 as strong cornering can cause bubbles in the system.

DOT 5 also can kill the hydraulic brake switches...why I don't remember but it was explained to me once.  

The use of DOT 5 might be the cause of your problems.  

Edited 37 minutes ago by Gunslinger

[mfg]

Guslinger made some good points… Also, those hydraulic switches commonly fail… When in doubt… change it out!!!

Or convert to a mechanical brake light switch.

[Gunslinger]

The hydraulic brake switches suffer from a dual problem beyond aversion to silicone fluid…current ones are made offshore now and simply don’t last…and original, well made switches are old enough now that they’re suspect in how well they work for any length of time.