Emergency Brake Light?

[patwreck]

Hello fellow 914ers

I just did a complete brake job on my 1970 914.

I Bought the Super Brake Kit from pelican parts and a new Master Brake Cylinder, had the calipers rebuild. etc.

Long story short I picked up my car this morning from the porsche dealership and now I have this red light on.

I remember this light coming on before I had my brakes done whenever I pressed my brakes really hard.

Please tell me what that red light in the 11 o'clock position is , and if i should take my car back to the dealership to get that light checked since i just paid 1300 for labor.

pic enclosed.

[Dave at Pelican Parts]

That light should blink under two circumstances:

1 - If the handbrake handle is not pressing the button underneath it. In other words, if the handbrake is still pulled up.

2 - If the brake master cylinder has encountered a loss of pressure in one of the two brake circuits. This usually happens when the brakes are bled; the light will start blinking and the switch on the master cylinder will need to be reset.

Pelican Parts: Brake System Reset

I have heard some reports that in early (1970 and maybe 1971) 914s that the light blinks in one of those two circumstances, and flashes in the other. I have very limited experience with the early cars so I cannot confirm that.

It also looks like part of the light is blocked off for some reason. I don't know why that would be.

--DD

[patwreck]

Originally Posted by Dave at Pelican Parts

It also looks like part of the light is blocked off for some reason. I don't know why that would be.

--DD

I believe that is another indicator light.

In the manual it says gas indicator light, oil light, emergency brake light, alternator light.

now i know its not the gas or oil light those are clearly marked. I am having a hard time figuring out which is which.

Like I said before in the OP this light was never on until I got this brake overhaul. But it would come on sometimes before when I would brake really hard, then go away. Now its just on and steady.

I am going to do some more research over the weekend and most likely call the dealership to have them sort this out.

[John Rogers]

As Dave noted, the switch under the handbrake can cause a red light, the switch can cause it and both are easy to check. Since you had a Porsche dealer do the work I would take it back and ask them to fix the issue. If they want to charge I would be surprised although most young P-car mechanics probably don't know anything about 914s so hopefully they have an old guy like Dave or me. If there is NO reset button on the m/c then it is the switch under the brake handle. If that tests okay then your last resort is to pull the bulb since it was installed to make the US government happy anyways and is not needed as real 914 owner knows when their brakes are working!

[Dave at Pelican Parts]

Originally Posted by patwreck

In the manual it says gas indicator light, oil light, emergency brake light, alternator light.

The oil light is the green one on the left that says "OIL". (Go fig! )

The alternator light is the red one on the right that says "G".

The brake light is the large red section at the top.

The low fuel light is the orange section on the left side of the fuel gauge. If the light comes on steadily, fill up even if the gauge says there is lots of fuel. The light is more reliable than the gauge.


Both of the circuits for the brake warning system work by grounding the wire that goes to the respective switch. So it is possible that a wire was knocked off of one switch or the other and is now touching a ground.

BTW, John is quite right about the pressure warning function of the light. The only time I've ever had it come on while driving was at the track, when I badly boiled the brake fluid. The pedal went straight to the floor, with little or no slowing of the car. And then the light started blinking. I cursed at it, because it was immensely obvious that I'd lost brake system pressure...

--DD

[Cairo94507]

I have never seen one light up 50% of the gauge like that-ever.

[TheCabinetmaker]

Originally Posted by Dave at Pelican Parts

The oil light is the green one on the left that says "OIL". (Go fig! )

The alternator light is the red one on the right that says "G".

The brake light is the large red section at the top.

The low fuel light is the orange section on the left side of the fuel gauge. If the light comes on steadily, fill up even if the gauge says there is lots of fuel. The light is more reliable than the gauge.


Both of the circuits for the brake warning system work by grounding the wire that goes to the respective switch. So it is possible that a wire was knocked off of one switch or the other and is now touching a ground.

BTW, John is quite right about the pressure warning function of the light. The only time I've ever had it come on while driving was at the track, when I badly boiled the brake fluid. The pedal went straight to the floor, with little or no slowing of the car. And then the light started blinking. I cursed at it, because it was immensely obvious that I'd lost brake system pressure...








--DD

Pressure warning light? I am only aware of the mechanical differential brake pressure system warning light in the four cylinder cars, and I suspect the six cars are the same (ie 911 style, simular to 914 style, just bigger)

the 914 warning system works by a free sliding piston that activates an electric switch, when ever the piston is moved off center position.
Each opposite side of the piston's bore are connected to the either the front or rear master cylinder bores via small drilled passages.

Two springs in the warning piston's bore hold the piston in the center home position,
When the brake is operated, pressure is immediatly built up in both front and rear brake systems which are seperate, using seperate master cylinder pistons. The pressure should be equal in both front and rear bores. the warning pistons stays in the center home position, with equal pressure on both sides of it.

If either front or rear system suffer a pressure lose due to leak or lack of fluid, or boiling fluid the different pressure between the front and rear system will overcome the spring pressure holding the warning piston in the center. When moved, the piston closes the switch and completes the warning light circuit..

When the pedel is let off and all brake pressure is removed, the warning pistons is returned by the holding springs to the center home position. The switch however will remain closed (ie light on) until the reset button on the switch is depressed.

Note there are some instances when the warning light will not work dispite failure. Of course a fault in the electirc portion will cause it not to function.

if however the seal between the front and rear master cylinder bores has failed, both bores will always see the same pressure, and thus a failure in front or rear system would not be detected. this leak between front and rear bores in the master can go undetected for years with out brake problems, until one side, front or rear fails, say starts to leak, and then the light wont indicate.

for best results check the fluid level each time you gas up, it is right there, no excuse not to. and keep up the brake maintanence.

some cars have a two wire electric switch at the master, some have a one wire. either can be used, as the two wires from the car are
1. ground
2. to warning light

the switch completes ground to the light
the single wire switch simply picks up ground thru the body and supplies that to the light whenthe switch is closed.

the warning light also lights up as a hand brake warning. this operates whenever the ignition is on, and the hand brake handle is in an up position, switch is under the handle base. again this switch makes ground, and is a one wire switch.

[Dave at Pelican Parts]

Originally Posted by TheCabinetmaker

When the pedel is let off and all brake pressure is removed, the warning pistons is returned by the holding springs to the center home position, and the warning light turns off.

There are switches where this is the case, but for most of the switches out there, the switch stays closed to ground once tripped. So even when you have equal pressure in both piston bores, the switch is still grounded and the light still blinks.

Those switches get reset by pressing the button that is on the switch itself. The button is usually covered by a rubber nipple, so you just push the nipple in and the switch gets reset.

--DD

[TheCabinetmaker]

Originally Posted by Dave at Pelican Parts

There are switches where this is the case, but for most of the switches out there, the switch stays closed to ground once tripped. So even when you have equal pressure in both piston bores, the switch is still grounded and the light still blinks.

Those switches get reset by pressing the button that is on the switch itself. The button is usually covered by a rubber nipple, so you just push the nipple in and the switch gets reset.

--DD

yes, your right, I forgot to add that, I will edit it the switch needs to be manually reset,
I was thinking of a late model VW Bug with dual circuit brakes. It uses a simpler system of two pressure switches, that were wired such that both have to be activated by pressure to not turn on the warning light. If only one of the two pressure switches sensed pressure, then the light would illuminate. this system did not have a latching warning light, when you pressed the pedel on a failed system, the light would warn you, but the light would go out when you let off the pedal
A Triumph I have owned had a piston type of warning system, like the 914, but mounted seperate from the master cylinder. There were no return springs to keep the free floating piston centered. On that car if activated, you had to manually reset the piston to turn off the light. That was a royal pain

Older cars often did not have a warning system. With single cicuit brakes of yesteryear, there was no need to warn you of a pressure loss , you knew it when you couldn't stop.

the dual circuit systems, that gave you two seperate systems had a flaw, if one system failed, the failure may not be noticed. Your back to having only one working system, if you have no indication of the failure of the other. If the rear brakes failed, and car not braked hard, the failure of the rear brakes may not be noticed, Thus the brake warning system was introduced

Some cars use a level sensor in the reservoir to indicate a failure, with a leak, there would be fluid loss, and that would trigger the lamp, no need to depress the pedal, just turn the ignition on to test, this is the least complicated system. It wont give a false failure indication for boiled fluid.

[Night School]

72 914 1.7 New guy thanks all of you. Both my top red lights are blinking/ flashing and. I can hear a relay clicking in time.
I guess I need to start with the brake system.