parking brake light?

[BerniniCaCO3]

Hah! How absolutely bizarre!
So; really, the parking brake light has been very dimly lit for weeks.
It was suddenly bright yesterday, hence the panicked posts.

Now, it just so happens, I tapped into a pink accy/run position on wire for my gauges and, why not, my trigger wire for the electric fan.
I noted before that the voltmeter read 10V.

So yesterday I installed a relay so that the weak pink accy/run wire wasn't supplying all the current, and my voltmeter and other gauges got 14V.

Now, yesterday, I also happened to leave the master cylinder wire unplugged.
Driving home, I noted that my gauges all were not working, along with the fan, so none of them had power.
I figured the pink wire had slipped out of the steering column harness-- it's kinda precarious.

Tonight I double and triple and quadruple checked that wire, and huh, no voltage on it, even when I was SURE I had contact.

On a hunch I plug back in the brake reservoir plug, and, gauges! And 7V on the pink wire!

There HAS to be a connection, and, quite possibly, the light is only due to low voltage on that ignition wire....
Time for wiring diagrams.
But it may just be that tapping into that wire lead to the parking brake light.

[86VickyLX]

[GM_Guy]

A friendly word of advice, especially since you are going into the automotive field;

DON'T JUST WILLY NILLY TAP INTO WIRES IN A CAR get a wiring diagram and find out what does what first. If that means waiting a week or two to get the information, so be it. Indisciminate choices for power in a car is a good way to let the smoke out of something, and you don't want to let the smoke out of something mission critical.

Alex.

[86VickyLX]

A friendly word of advice, especially since you are going into the automotive field;

DON'T JUST WILLY NILLY TAP INTO WIRES IN A CAR
Alex.

This!!!

[85crownHPP]

DON'T JUST WILLY NILLY TAP INTO WIRES IN A CAR
Alex.

words to live by

[mrltd]

And this is why I could give a fuck about someone being ASE certified working on my car.

[BerniniCaCO3]

real funny guys!
I'm taking the ASEs in november fwiw [for what it's worth].
Having worked at a shop for 3 months now, so yeah, I'm very green, I'd say that years' experience more than many things make the difference. And of course intelligence.
Lots of my coworkers are not ASE certified, and many of them I trust quite a lot.

[85crownHPP]

Admittedly, I also did not check that the float is there @ the proper height, i.e., not stuck at a lower level than the fluid.

Do this, after making sure your wiring is proper.

[85crownHPP]

So is the late-model master-cylinder warning switch just supposed to monitor fluid level?

Looks like it to me - the wires go into the reservoir itself and it definitely has a float. Im pretty sure the prop valve is the big in-line doo-hickey on the MC outlet for the rear.

[GM_Guy]

Brake light does three things, Fluid level (for cars with the float in the master. You got a wire going there, you gots a float), parking brake "on", and circuit pressure loss.

Circuit pressure loss being a single half of the system. Differential pressure on one side in the proportioning valve will cause a valve to shift out of center and trip the light. If both sides lose pressure, no pressure difference, valve does not move and wont turn on the light.

Alex.

[85crownHPP]

Except the 88-91 cars that have no proportioning valve with a pressure-loss sensor to trip a light

[1987cp]

And the fact that two out of two '87 models I've had didn't trip the light when the prop valve buggered up.

[BerniniCaCO3]

Just for future reference, what ARE the symptoms of a buggered proportioning valve (which I don't have), or, a buggered metering valve (which I do)?

[GM_Guy]

Thats because its not a prop valve failure light.

Alex.

[1987cp]

Just for future reference, what ARE the symptoms of a buggered proportioning valve (which I don't have), or, a buggered metering valve (which I do)?

NO rear brakes whatsoever was the symptom in both of my cases ....