'84 brake lights still coming on late

[BillyPilgrim]

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[n8marx]

Sounds normal to me. My '86 does the exact same thing you describe. Two different shops have told me that's normal operation for the pressure switch equipped cars.

I compensate by braking late and hard. That always gets the lights to come on. You can keep an eye on the brake light function by observing them in the chrome bumpers of the pick-ups behind you. In most normal braking situations mine do come on. Just not in the slow rolling stop situations.

Good luck.

[Jdub]

It is a weak point with these cars. All I can say is to bleed the system, including the two holes into which those switches went. There is always the slight possibility that you have muck in the bottom of the MC. This stuff cannot be pumped out via a standard brake bleed -- you have to bleed the switch holes.

The point at which the plate inside each switch contacts internally and forces a brake light varies between lots. You may just have a "bad" set.

John

[don911]

I've only noticed delayed brake lights when the switched are failing. Mine seem to fail almost yearly. I don't agree that delayed lights are normal. Mine come on as soon as pressure is applied to the pedal.
Did you bleed the air from the system when you replaced the switches? Maybe some air is trapped in there somehow. Other than that I don't know....bad switches or possible dirty connectors?
I have two new 3 prong switches that I can't use. They came with a turbo M/C. I think I remember a post on how to use the 3 prongs on a carrera. If there is a way, you can have these so you can test to see if you got some bad switches.

[masraum]

It's not normal for them to come on late. I agree that the only things that I can think of would be bad switches, air in the system (need to be bled) and crud in the ports. good luck.

[masraum]

The brake fluid will only flow out slowly, but I switched mine as quickly as possible. The system is not under pressure unless the you actually have the brakes on.

The front and rear brakes actuate at the same time. If there is air in the ports then the air will compress, but if the brake lines to the wheels are well bled then the brakes will apply.

[Jdub]

The difference between when the front and rear come on is what causes your Brake warning light to come on -- it is a message that one system (front or rear) has/is failing.

The switch uses a round plate inside that, when pressure is applied to it, grounds the connection and forces the light. Thus, if the tolerance of the spring that forces the plate back to normal position is different either between switches or between manufacturing lots, you will have either 1) differing switch "on" state between switches or 2) a piece manufactured out of spec.

Sadly, it is the VW switches that have given me the earliest "on" state but they are also cheaply made at $6.00 a pop and fail within a year.

You might try taking your old switches and cleansing them with contact cleaner. You have to put a pin in there to open the plate to get behind the plate and force out the junk.

Finally, whenever I swap my switches I have someone putting positive pressure at the pedal EXACTLY when I pull the switch. I quickly screw in the new switch, then do it again to purge the MC.

John

[911jeff]

Originally posted by Jdub

Finally, whenever I swap my switches I have someone putting positive pressure at the pedal EXACTLY when I pull the switch. I quickly screw in the new switch, then do it again to purge the MC.

John --

Would you elaborate on this? I'm assuming that you have someone hold the pedal down as you remove the switch(es) -- how does this help? Does that mean that you don't hae to bleed the system afterward? Or does this just somehow help clean out the crud in the MC that caused the switches to go bad in the first place. How does this purge the MC?

I just had my system bled due to a clutch master cylender replacement, then found that the brake lights weren't working. I hate to have to bleed 'em again.

Thanks for your help.

[vash]

wait, i dont know much about the newer cars. ignore me if i am an idiot, sorry. when we are talking about brake lights, are you guys talking about the light on the dash or the brake lights out in the back of the car? did they change the pedals? is there no light switch on the brake pedal inside the car? i had to adjust the switch on the pedal in order to get it to work properly. simple with a conductivty beeper.

cliff

[911jeff]

My rear brake lights are out, and on the '87, the lights are switched by two redundant hydrolic pressure switches bolted into the side of the master cylinder.

There is not a simple microswitch on the pedal -- that would be too easy!

[vash]

oh man, that sounds tuff. good luck jeff!
i think if you put some pressure on the pedal, you minimize the amount of air that get into the system.

wow, that is incredible. good luck.

cliff