brake indicator light glows intermittently in dash- ideas?

[Low Elco]

The light just glows when key is on. It just started this. it works brightly as advertised when the ebrake is on, and turns off with it. Im sure it's sneaking voltage from somewhere, but idk. anyone got any ideas?

[mongocanfly]

Copied this off another sitemaybe itll help......
Brightest – park brakeMedium – Combination valve (aka metering & proportioning valve)Dim – RWAL SystemWatch the light very closely and apply the parking brake. Did the light get brighter?*When the key is first turned on the RWAL module turns the dash brake indicator light on for 2 seconds, then it should go off.You can unplug the wire on the Combination valve to see if it is the cause on the light coming on.
There are three brightness levels of the dash brake indicator light on RWAL equipped trucks.Brightest – park brakeMedium – Combination valve (aka metering & proportioning valve)Dim – RWAL System

[hatzie]

Originally Posted by mongocanfly

Copied this off another sitemaybe itll help......
Brightest – park brakeMedium – Combination valve (aka metering & proportioning valve)Dim – RWAL SystemWatch the light very closely and apply the parking brake. Did the light get brighter?*When the key is first turned on the RWAL module turns the dash brake indicator light on for 2 seconds, then it should go off.You can unplug the wire on the Combination valve to see if it is the cause on the light coming on.
There are three brightness levels of the dash brake indicator light on RWAL equipped trucks.Brightest – park brakeMedium – Combination valve (aka metering & proportioning valve)Dim – RWAL System

No such thing as RWAL on these trucks.
The proportioning valve switch or E-Brake pedal switch grounds one side of the brake pedal lamp.

It could be as simple as a short to ground in the wire running to either the E-Brake or the proportioning valve switch.

If the E-Brake pedal isn't retracting fully it can make the BRAKE lamp light dimly.
If the E-Brake warning switch is worn it can make partial contact with the pedal all the way up.
Pull the RELEASE handle and lift the pedal. If the lamp goes out you need to lube the pedal and cables.

[mongocanfly]

Yeah I know they didn't have rwal...thought the part about the proportioning valve dim light might help but what your saying is that don't apply either..

[rich weyand]

These sorts of things are often caused by ground issues.

These trucks have four things that need to agree on ground: the frame, the engine, the battery, and the cab. They are electrically isolated from each other by engine mounts, cab mounts, etc.

Four things agreeing on ground means three ground wires to connect them.

Stock ground wires are: 1) large ground wire from the battery to the alternator bracket; this grounds the engine and the starter to the battery; 2) small ground wire from the battery to the radiator support; this grounds the frame to the battery; 3) copper braid from the rear of the passenger cylinder head to the cab; this grounds cab to the engine, and thus the battery.

If one of these is missing, you can get all kinds of gremlins. My favorite is the gas gauge that swings back and forth with the turn signal flasher.

The one that's missing is usually the one from the engine to the cab. Second favorite is the one from the battery to the radiator support, which goes astray if someone gets a new negative battery cable without the extra ponytail on it.

[foamypirate]

Originally Posted by hatzie

No such thing as RWAL on these trucks.
The proportioning valve switch or E-Brake pedal switch grounds one side of the brake pedal lamp.

It could be as simple as a short to ground in the wire running to either the E-Brake or the proportioning valve switch.

If the E-Brake pedal isn't retracting fully it can make the BRAKE lamp light dimly.
If the E-Brake warning switch is worn it can make partial contact with the pedal all the way up.
Pull the RELEASE handle and lift the pedal. If the lamp goes out you need to lube the pedal and cables.

91' squarebody Suburbans actually did have RWAL. Just thought I'd throw that out there, lol.

[Dead Parrot]

Don't overlook the possibility that you DO have a brake system issue. The light could be dim because the wiring between the light and the prop valve switch is bad or the "it's bad" switch in the valve is itself bad or deteriorated.

Especially if it keeps coming on after you verify good grounds.

[v30crewcab]

the reason for the light is to come on when you have a brake leak and the prop valve goes all the way one way. so maybe you should make sure you don't have a brake leak first! anything wet around the backside of one of the wheels?