parking brake light?

[BerniniCaCO3]

Starting tonight, the parking brake light seems stuck on. Parking brake is not pushed in.
I presume there's some switch built into the pedal, that is stuck in some position? I tried looking briefly but nothing stood out.
Does the light come on when the switch is depressed (therefore, something must be holding it up), or open/released in some fashion (=broken, or somehow mispositioned)?

Kinda irritating already


thanks!
-Bernard

[86VickyLX]

Starting tonight, the parking brake light seems stuck on. Parking brake is not pushed in.
I presume there's some switch built into the pedal, that is stuck in some position? I tried looking briefly but nothing stood out.
Does the light come on when the switch is depressed (therefore, something must be holding it up), or open/released in some fashion (=broken, or somehow mispositioned)?

Kinda irritating already


thanks!
-Bernard

Pull up on the parking brake pedal they get stupid sometimes. Or you have a brake problem.

[BerniniCaCO3]

where is the sensor?

[86VickyLX]

where is the sensor?

Master cylinder or prop valve underneath it. Check fluid level.

[1987cp]

Yep, definitely unplug the distribution-block sensor and see if the light goes out. It's intended to indicate partial service brake failure, as in no brakes either front or rear, but I had two different ones quit sending pressure to the rear entirely and never turned the light on!

[BerniniCaCO3]

OH-- so the parking brake light does not just = parking brake is on?
it's also a general brake failure light?

I mean, I can put someone in the car on a lift and see if, when they step on the brakes, all wheels lock up-- that should be a comprehensive test right? Or not necessarily?

[1990LTD]

Yeah it's for brake failure

[1987cp]

OH-- so the parking brake light does not just = parking brake is on?
it's also a general brake failure light?

Yes.

I mean, I can put someone in the car on a lift and see if, when they step on the brakes, all wheels lock up-- that should be a comprehensive test right? Or not necessarily?

Nope, because it takes very little braking force to prevent you from turning the wheels by hand. I doubt you'd learn anything useful from such a test unless the front or rear brake circuit is completely non-functional, and you'd notice funky braking long before that point (I hope).

First, attempt to lift the parking brake pedal while pulling the release lever, since they do like to jiggle downward and engage the light, and if it doesn't go out, try unplugging the underhood brake light sensor (it's in the thing that has brake lines going into it).

[BerniniCaCO3]

OK-- took a minute just now!

Found that there was, indeed, a switch for the parking brake itself. It's behind it; single wire, pink and green (faded red maybe).
Unplugged that.
No change.

Found a 3-wire plug right off the master cylinder.
Unplugged that.
No light.

Problem fixed! Just kidding.

OK-- so something's going on with the master cylinder.
Fluid was flushed over a year ago. Fluid level is still just under max. S'pose it's possible that it was over max a year ago and has been leaking very very slowly indeed... but seems unlikely.

So I shouldn't have a brake line failure, correct? Or I'd have lost a LOT of fluid.

Now I'm studying for the brakes ASE this november and was just rereading up on this.
Since i have front disk/ rear drums, I have a metering valve.
Is this the only cause left? Or a faulty sender of some sort?

Since I haven't noticed anything, and fluid level is not perceptibly diminished, I can only conclude that pressure might not be being proportioned correctly between front and back? Does that sensor, and that warning light, check for that?

Classic nose-diving I haven't noticed, but then, it's a heavy and more balanced car than a small sedan with soft springs that might nose dive a lot. Hmm, and I might have an excuse for those two cars I slid into last spring when the brakes just locked right up Maybe not.

Anyway, what next? Master cylinder R&R?

[BerniniCaCO3]

Or; there is a sensor on the brake pedal (not the parking brake pedal). Green wire and Gr-R wire coming out of it. Could that be bad?
I want to fix this efficiently, but, want to cover all my bases before yelling "master cylinder!" and wasting my time & $$ if that wasn't it.

[BerniniCaCO3]

inspected brakes themselves a year ago; put new front brakes & rotors, and, ended up doing nothing to the rear, as I opened up the drums and the pads looked like new and the wheel cylinders were not leaking at all.

[86VickyLX]

1. fill master to max
2. the 'sensor' on your brake pedal is for your brake lights lmfao.
3. if problem persists, bleed your brakes.
4. if problem still persists, grab ankles and kiss ass goodbye.

[1987cp]

Not at all familiar with setups having a sensor on the master cylinder. The only brake warning switch I've seen in person is the one I described, that lives in the distribution block down on the framerail. So I assume your car must be one of the later ones with the newfangled master cylinder with the plastic reservoir.

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

[86VickyLX]

Not at all familiar with setups having a sensor on the master cylinder. The only brake warning switch I've seen in person is the one I described, that lives in the distribution block down on the framerail. So I assume your car must be one of the later ones with the newfangled master cylinder with the plastic reservoir.

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

No. The only ones I saw that had a fluid level sensor were ABS panthers. Unless the prop valve is in the master cylinder.

[BerniniCaCO3]

I'm not dense-- I know that some cars use the brake pedal sensor not just for brake lights, but to inform the computer that you're trying to slow down, whatever that may entail for engine trimming, trans shifts, etc. I thought it could have been something more.

Yes, it is an aluminum master cylinder with a plastic reservoir. 1990 panther.
There's a plug that goes into the master cylinder. 4 lines come out of the master cylinder (unsurprisingly). I don't know that there IS an independent distribution block??

The plug that goes into the side of the cylinder has 3 lines.
Fluid is at max level.
I can overfill it a little bit.

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.

But aside from that, what DO the three wires tell me? Just fluid level, or more?