TheSamba.com :: View topic

Mon Jan 23, 2012 5:00 pm

I took my 69 bug in a couple weeks ago to have the brake master cylinder and rear wheel cylinders replaced. After I got the car back, the brake pedal only goes down about halfway what it used to, which is good--except for one thing- I don't have rear brake lights anymore unless I absolutely MASH the pedal, and I can't do that while driving.
Does anyone know if the rear brake light switch contact off the foot pedal is adjustable and where it is located? Thank you!

Mon Jan 23, 2012 5:13 pm

The master cylinder in located on the other side of the firewall across from the brake pedal. The brake light switches are on the master cylinder. The switches operate off of hydraulic pressure when you press the pedal. There is no adjustment. They may or may not have a rubber protective boot on them. Did you have problems with the lights before the repair?

Mon Jan 23, 2012 5:13 pm

You hopefully have two identical hydraulic switches - either 2-prong or 3-prong...no adjustments may be made to the switches...One of the the dimensions that is adjustable, that is generally checked and altered infrequently is the pushrod freeplay:

http://www.vw-resource.com/adjstrod.html

Mon Jan 23, 2012 5:15 pm

Odd. Maybe someone will learn me on this, but I was under the impression that the brake switches worked from fluid pressure when you press the pedal down, so even the slightest bit of pressure will turn the lights on. Maybe your rear switch is bad if it's a dual circuit master.

Mon Jan 23, 2012 5:16 pm

Did the shop use new brake light switches, or did they re-use your old ones? I've had some in the past that required stomping on the brake pedal to get them to light. Some think that an air bubble might form when screwing them in, like to dab them wet with brake fluid first.

I ended up buying a new pair of switches from BAP (local) and they have seemed to work better. Now I'll have to check them again.

Note that on a VW that they only light when the ignition is on and the pedal pushed.

Mon Jan 23, 2012 5:58 pm

Vinnems wrote: I was under the impression that the brake switches worked from fluid pressure when you press the pedal down, so even the slightest bit of pressure will turn the lights on. Maybe your rear switch is bad if it's a dual circuit master.
They do work off pressure, but the MC must build enough pressure to overcome the internal spring and diaphragm to close contacts. It normally doesn't take a lot of pressure to close the contacts so I'm also thinking a problem with the switches, or an air bubble?

The output of the two brake switches eventually come together as a single wire to both rear brake lights. Either brake switch can activate the brake lights. OP, you should test boothe separately to see if maybe one is broken and the other takes excessive pressure to activate. You could also try bleeding the MC att the switches to remove any air. Take it back to the shop to do this.

Mon Jan 23, 2012 6:54 pm

Thank you guys for all the responses and info. I didn't realize the brake lights were fluid pressure activated. I didn't have any problem with the brake lights before the job, but my pedal was going down almost to the floor so i just assumed the difference in pedal travel from then to now was the cause.
I can take it back to the shop and have them bleed the system and see if it makes any difference. I think my dash mounted brake system check light is broken also-- it does not light up when I depress it-- but that was happening before I took the car in for the brake job, and I had rear brake lights then without having to stomp the pedal, so I figured that didn't have anything to do with it.

Mon Jan 23, 2012 7:02 pm

Cusser wrote: Did the shop use new brake light switches, or did they re-use your old ones? I've had some in the past that required stomping on the brake pedal to get them to light. Some think that an air bubble might form when screwing them in, like to dab them wet with brake fluid first.

I ended up buying a new pair of switches from BAP (local) and they have seemed to work better. Now I'll have to check them again.

Note that on a VW that they only light when the ignition is on and the pedal pushed.

I looked on the receipt from the shop but there is no mention of whether they reused my old switches or installed new ones. I can call them tomorrow and ask. I knew they wouldn't light at all without the ignition on-- when my neighbor first told me a few days ago that I didn't have any brake lights (he saw me drive past and pull up to the stop at the end of the street with no brake lights) I thought I had lost them completely when I was checking it, because I kept stepping on the pedal normally. Only after a REALLY hard push on the pedal (basically pushing myself against the backrest of the driver's seat) did I get them to activate.