Park Brake light on and does not go off.

[loschatz]

1981 Z 28 Camaro
Park brake light came on and does not go out. Park brake is not engaged... verified many many many times!
So I'm contorted under the dash and this is a "one wire in" type switch which is activated by depressing the center "pin" of the switch.
I think possibly it just needs adjustment as maybe I hit it with my foot getting in or out. Fiddled around....No difference....then ....yesterday...coming home from a car show the light goes out! I happened to be driving it home in the rain. Today after everything dried out the light is back on.

OK I'm generally not to bad with electrical but this has to be a ground issue which can be a hair pulling event! I have found and cleaned three chassis grounds hoping to stumble onto the magic one. One from frame to battery, one which is under the floor mat on drivers side and one that is for the cruise (yeah I know, has nothing to do with this but I cleaned it anyway).
No difference.
BTW, everything on the vehicle that is powered works. All lights, tattle tail indicators, etc.

Reaching out to whomever has battled this small but annoying problem.
Where the hell do you start? If this is a common problem then the answer must also be common.
I have a new OEM park brake illuminator switch but really don't think this is the answer as I am convinced its a ground problem.

I assume these things work such that power is always going to the switch through the light itself on the single wire (brown, for anyone that cares) and when peddle is depressed the switch grounds and light comes on? Correct me if I am out to lunch here.

Any help on this will save me time.

 

[Twisted_Metal]

You are correct... If the circuit "finds" a ground... The light comes on.

But... There are TWO switches on that circuit and either (or both) will cause the light to be "ON".

The other switch is at the proportioning valve, by the brake master cylinder.

Your grounds are fine but the wire to the parking brake OR the proportioning valve is finding a ground somewhere along their paths.
Unplug the switch at the parking brake... If the light goes out, it must be the other one.

Repeat the test for the proportioning valve switch and you should be able to narrow it down to one of those brown wires.

The only other cause would be something wrong at the printed circuit panel at the back of the cluster or the plug to the cluster.

Good Luck!

 

[70lt1z28]

Might also check the spring on the cable under the car. If it is broken or missing the pedal is "lazy" and does not pull all the way up tight. you can though easily verify this with putting your foot under the e-brake pedal and pulling up. If the light goes out, look under the car to check the spring. Otherwise, Twisted's answer is spot on.

 

[Burd]

My 78 light stayed on, it was the switch. When you release the brake, it slams into this tiny switch. They get bent. Prob disco’d now. I got one from a dealer

 

[Burd]

Here’s a spare I pinched from a Camaro while getting a seatbelt buzzer for my car

 

[loschatz]

You are correct... If the circuit "finds" a ground... The light comes on.

But... There are TWO switches on that circuit and either (or both) will cause the light to be "ON".

The other switch is at the proportioning valve, by the brake master cylinder.

Your grounds are fine but the wire to the parking brake OR the proportioning valve is finding a ground somewhere along their paths.
Unplug the switch at the parking brake... If the light goes out, it must be the other one.

Repeat the test for the proportioning valve switch and you should be able to narrow it down to one of those brown wires.

The only other cause would be something wrong at the printed circuit panel at the back of the cluster or the plug to the cluster.

Good Luck!

Ok I did as you suggested. I disconnected the power wire from the switch going to the proportionator. Light goes off. I put a jumper between the power wire (brown wire) and ground. Light goes on. Ok so wiring appears fine. I then took a continuity test and there is continuity between the male pole of the switch itself and ground. So....either the switch is stuck in the closed position (going to ground all the time which forces the light on) OR there is really something messed up within the proportionator/brakes which is forcing the switch to close and go to ground. No idea why the problem went away while driving in the rain, then came back when everything dried out....hmmm.
What do you suggest is my next step?
My brakes seems/feel "normal". I am not 100 percent sure on the purpose of the switch at the proportionator? I believe the device itself is to regulate flow of oil to either front or rear brakes OR both if brake pedal is applied with force.

 

[loschatz]

Here’s a spare I pinched from a Camaro while getting a seatbelt buzzer for my car

Yup...got one of them! The problem seems to be the switch at the proportionator or the proportionator itself.

 

[Twisted_Metal]

Well... You now know which switch is triggering the brake light.
Unfortunately... It's not the simplest of scenarios.

The switch at the proportioning valve (or combination valve, in this case) finds a ground when there is unequal fluid pressure between the front and rear portions of the braking system.

Here's a (generic) cutaway view...

When the "Pressure Differential Valve" moves in either direction (due to a variance in pressure between the two ends) the little nub of the brake switch will contact one side or the other of the detent in the valve, where it's supposed to be.
This movement grounds the circuit for the brake warning light.

This switch itself rarely fails but I guess it's possible.

You may be low on fluid in the master cylinder or you may have a little leak somewhere. <-- Check fluid level first.

If one side of the master cylinder is very low... You need to inspect that end of the car for leaks.

The light doesn't tell you if it's the front or the rear causing the issue so you need to inspect everything for leaks.
Lines, connections rear brake cylinders and front calipers.

 

[loschatz]

Update
The master cylinder oil reservoir was full and even front to back.
Took car to shop to get brakes checked. As you might expect...light was on while driving there and when tech went to move car to hoist the light was off! It did come on again later after he shut off the car and restarted. Odd.

Everything appears normal with the braking system. No leaks and brakes function just fine. Lots of pad left.
I believe only option is that it is the switch itself which I will try to hunt down from a wrecker. It looks like I would have to buy the whole proportionator (that is...if I could find one) as the switch itself does not have a part number...or so I'm told!
Until then, I pulled the power wire and will carry on with life.

If it wasn't for the on again off again issue, I would think about a brake flush just in case there is some crap in the proportionator that gets between the switch and the proportionator casing itself, causing it to ground.

Anyway thanks for all the help on this.

 

[Twisted_Metal]

I believe you can remove the switch and check to see if there's some crud on it.

You shouldn't lose any brake fluid as there are seals on either side of the differential valve within the combination valve.
(If fluid leaks out, you probably need a new valve anyway.)

A brake flush won't clear that area but an air compressor blown in there might.
If there's some rusty scale or something causing the the grounding it might get blown out.

This might be the right switch...

1978-1986 Disc Brake Valve Warning Switch - For all GM Cars and Trucks, Each

1978-1986 Disc Brake Valve Warning Switch - For all GM Cars and Trucks, Each

www.inlinetube.com

Summit sells the combination valve but make sure it's correct for an 81.

CHEVROLET CAMARO Summit Racing SUM-760186 Summit Racing™ Brake Proportioning Valves | Summit Racing

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