I replaced the power brake booster this past weekend due to a hissing sound (see other forum posts for details). The hiss is gone, but I've now encountered another issue that may or may not be related: the brake lights stay on because the brake pedal no longer engages the brake light switch.
There is now about a 1/4" gap between the rubber contact pressure plate on the brake pedal and the plastic cylinder/plunger on the switch. In other words, the car thinks the brake is being pressed. I have worked a temporary fix, but does anyone know if the brake pedal can be adjusted and/or if the switch can be? I am going to pick up a new switch in the meantime to see if there's any difference between new and old (will post findings here), replacing if necessary, but it seems awfully coincidental that this happened immediately after replacing the booster.
Thoughts?

 

Why do you think another brake switch will help?

Obviously it worked before the booster replacement, so something is different, but why the switch?

My wife has the Trib at the moment so I will not be able to check it out now, but is the booster plunger a bit shorter on the replacement and thus pulling your brake pedal away from the switch?

Any adjustments for the switch position or its plunger length?

 

It crossed my mind too that it's certanily possible the booster plunger is shorter on the new one; it is a remanufactured part, after all, purchased from an auto parts store. Thankfully I haven't turned the old one in yet so I could compare the two, but without uninstalling it (which I could do in the end if all else fails), I was hoping there may be a way to either adjust the pedal or the switch, neither of which I've figured out a way to do. Start with the cheapest/easiest, then work from there I guess. Thanks in advance for checking your switch...

 

The replacement booster had a rod that engages the master cylinder; the instructions said to ensure the length matches the length of the rod in the original booster. If you didn't compare these two then that may explain this new issue. It's possible the switch contact point got moved and could simply be adjusted so the brake lights go off, but if the brake pedal is sagging or has too much play in it you may have to remove the master cylinder and adjust the new booster's rod length; compare/adjust the rod length to match the old one. Good luck.

 

Thanks. Any idea on how to adjust the rod length? Special tools required? The brake pedal does seem to have more play than usual, but thankfully the car stops just fine until I can take a look. I guess if I have to pull it all apart again it's a good thing I bought extra brake fluid!

 

It was the switch. I bought a new one and compared the two - the difference was obvious. The plastic plunger that comes into contact with the brake pedal had somehow been pushed too far back into the switch housing (approx 1/4" or less was showing). This time, I pulled the plunger and it popped all the way out (approx 1", maybe a little more), matching the new one. Put the old switch back on, conected the electrical, and voila, problem solved.

Be aware it may take some effort to get the plunger pulled all the way out...it didn't work when I first posted this thread. Also, it'll click as it's pulled out and the pedal will reset the length appropriately once reinstalled.