Dash Panel brake Light

[MrD]

Well I have never seen this before:

84 BII
Lately while driving when I step on the brake sometimes the dash brake light comes on, then it might stay on , then when I step on the brake pedal again it goes off.????

Today when I started it the brake light came on and stayed on until I touched the brake pedal.

I am thinking a short, because if I leave the emergency brake on, start it up and let it idle no brake light is on.

I can drive down the road with the interior dash brake light going on and off at random, slam on the brakes and get a great stop almost knocks you out of the seat.

Any ideas....

[Ruffinit]

You might be at the threshold of low brake fluid. The sensor may be sensitive. My 84's windshield washer res sensor drove me nuts. Ended up being the sensor. But it's common for it to blink like this if you are close to needing some. Just check and add a bit if it's close.

[1986_bronco2_4x4]

my 84 does the exact same thing except my brake lights also wont go off...

[neb_scot]

My 84 BII does exactly the same thing - its on permanently. The break fluid res is full, although the fluid is black as can be. My breaks, although not the most responsive, do operate fine. The interesting thing is the previous owner cut off the emergency brake cable at some point. Its completely gone so I dunno if it could be that. Ive taken to trying to hide the light with tape as its real distracting when driving.

[Ruffinit]

One of the guys on a different post suggested that this may stem from the proportioning valve which would be why in most cases the brakes would still work. It's cold and snowy outside, so I'm not gonna check it on my BIIs, but if you have a warm, dry place, you may take a peek and see if somethings up with it. I don't know if an autoparts place would have one on hand that you could take a look at (read nice and clean) and don't have any idea of a cost, but I think these are junkyard only items. This could be a sensor or sensor wiring that may hook to it. Here's a bit of tech from the Bronco site (early). I would expect that it is the same with the BIIs:

"..how does this switch work inside the valve?"
The pressure diff. valve has a piston inside it that has an "indent". When press. is un-equal.., the piston moves (to the weak side) & activates the light.

"Is the light supposed to come on if brake failure?"
That would be a bit late.... It illuminates to warn of pending/developing issues in the hydraulic system.

[tekatlarge]

Quick check of the valve and light would be to disconnect the wire going to the valve and see if the light goes off.

[MrD]

UPDATE

I bled the brakes. The right rear even made an air sound x 2.

The brakes are awesome and no dash light anymore.