Brake lights come on for no reason

[Warren Webb]

No hill holder or brake fade. The push rod has around 1/8th" movement before contacting the power brake booster.

[BILT4ME]

I used to have this problem on my 59 Lark where the MC is located under the floor. I discovered it was an alignment issue where I had a spacer on the wrong side of the MC and it caused a bind between the rod and the piston inside the MC. Figured out the correct spacer location per the Shop Manual and problem solved.....35 years later! Back when, I could do the "Fonzie jukebox-on move" on the front fender to get the lights to turn off.

Your is mounted on the firewall, so you may not have the same issue. I would definitely look into a new brake-return spring, lubing the pivot, and maybe a new sender. You may also still have air in the system that is expanding, causing the pressure to increase on a hot day.

Good luck!

[karterfred88]

No hill holder or brake fade. The push rod has around 1/8th" movement before contacting the power brake booster.

When they come on, they go off if you bounce the pedal, just put in a new switch. Or convert to a manual electrical contact switch at the pedal--best way. The quality of the hydraulic switches is so poor now a new one could start doing the same thing, and the pedal switch will never leak either.

[jpepper]

I think the pushrod on the power booster is adjusted wrong. It is a little too long not allowing the piston in the master to fully retract and open the return port. Heat causes expansion and pressure builds which turns on the light. With the lights on, loosen the master mounting bolts. If the lights go out, it verifies my assumption. Take the master off the booster. You will notice the pushrod has an adjustment screw at the end. There is a specified length in the shop manual. The piston in the master should not compress at all when the master is held flush to the face of the booster. While the master is off check to make sure rust, corrosion, and/or dirt has not built up between the piston and the retaining ring on the master. This too can prevent full return of the piston. Clean it if necessary.

[Jeffry Cassel]

change switch. If it is still a problem and brakes are adjusted ok consider the turn signal switch . The brake light circuit is routed thru the turn signal switch and lots of weird stuff is caused by a bad turn signal switch.