tyssniffen

while it seems my e-brake is not on, and I have checked the little foot-pedal-circuit-connector to make sure some sort of connection is wrongly being made, the dashboard indicator lights are on all the time.

How can I check to see if this is just some electrical issue, or if there's something wrong with the.. sensor? .. that detects if the brakes are locking up?

or, could there really be something going on with my brakes?

I drive a lot of dirt roads, so wondering if something has gunked up the system, or what.

edwinsmith

It could be the ABS or Rear Anti-Lock system is messed up, or your proportion sensor says either your front or real brakes are out of fluid. To check if it's the ABS unplug the module behind the glove box. If the light goes out then there you go. Also check the fluid levels in your brake master cylinder.

bigragu

TYSniff, check post number 34 on DanS's tread on him picking up another first gen just 10 minutes ago. He is having the same situation as you somewhat, and I posted up what to check on his 1993 model truck.

If yours is that 1991 I see in your sig, that combo valve is mounted down low, under the master cylinder, but behind the drivers side frame rail. Just follow down the brake lines from the master cylinder, you'll find it along with the brake switch mounted on top of it.

tyssniffen

ok, well, the ABS light goes out when that module is unplugged. the ebrake light does not.

so... where does that get me?

bigragu

You have issues with one of three things, and to quote Jmartin- that brake light is handles by three switches. One is the low vac switch, which if you followed the vacuum line off of your brake booster, you'll see that it heads to your cruise control servo, then tees off towards the fender well, divers side. Underneath the hood spring is that low vac switch. If you have any cuts or holes in any of your vacuum lines, or if your vac pump is not working to spec, that will trigger the brake light switch. You also could have a faulty booster manifold, which is that plastic bung pressed into your booster that all the vac hoses dive into. That highly unlikely, though.
The second is the switch on top of your brake differential combo valve. You may have a hydraulic leak in either your front or rear brake lines, or your rubber brake lines that came from the factory are old, nasty rubber that won't hold pressure cause it's basically disintegrated on the inside. The hoses, if original, will swell every time you push down on the brakes, possibly causing uneven pressures in the hydraulic systems. Check every connection that the brake lines attach to, including calipers up front and your wheel cylinders inside your drums. Also, poorly adjusted shoes to drums will trigger this off. Since I'm on the brakes, how's your pedal pressure? How does your brakes work? Like I described in that other tread, if the metering valve shifted off center, it will trigger that brake switch and illuminate that brake light.
The third and last switch that illuminates that light is your emergency brake pedal.

I believe JMartin described how to do a functionality check, by using the process of elimination- disconnect the brake switch on your brake combo valve first, if light still illuminates, reconnect the harness to the brake switch then disconnect the low vac switch. Something like that.
Remember, you'll need to be pushing down on the brake pedal at each test.


Another way to see if it is that combo brake switch shifting off center, triggering the brake light, is to connect to your battery positive with a lighted probe tool. Touch the probe onto the brake switch(harness disconnected) pin. If your tool doesn't light up, your metering valve is centered and it's not that. If your tool lights up, then it has shifted due to all the items I've described in checking the brakes Hydraulics. If that valve has shifted, that means only one of your brakes are working and taking up the load, either the rear circuit or the front circuit, but not both equally, which means less than optimum brake quality.

edwinsmith

A problem with some of those test lights is they use an LED which will depend on which way the current flows to light up. A Bigragu suggested connect your probe to the battery positive and tough the probe to battery negative or a good ground to make sure the probe lights. If not swap ends on the probe. If your probe has a regular light bulb then no problem.

Edwin

tyssniffen

thanks for all this. I will dig in and see if I can figure stuff out.

the rig does seem to brake fine... pedal is still solid, etc.

**** here's another little clue - This has happened before, and then gone away. That is, it seemed the light was on for a few weeks (I don't drive that often) and then went away and worked 'properly' for a number of months. now it's back to being on all the time.


that's why I keep thinking it's just an indicator problem rather than a true braking problem.

bigragu

What time of year/season was it when the brake light did not come on, meaning "worked properly" based on your description?

Blue Goose

just for s&gs....pull up on the e brake pedal.....all my old mopars have needed the switch on the pedal adjusted...

tyssniffen

sorry, I can't remember the specifics. are you going for cold or hot weather? I'm in Northern California, where it doesn't really freeze in the winter but it does get hot in the summer. still, I don't think it was seasonal like that.

bigragu

I, too, am in NorCal, and reason I ask is yes, I was curious about possibly higher temps affecting something. What, I'm still unsure of, in your trucks situation. I've given you all the advice I can, which came about from personal experience. Actually, I still am struggling with a brake light still on, but I've narrowed it down for sure to the metering valve shifting. I have three plans in the works to resolve this for good. Mine was self brought on, with my hydroboost conversion, so probably apples to oranges in our problems

edwinsmith

When my light was staying on I ran a computer check that showed the RWAL dump valve was defective. I didn't have the money or time to fix that so I just unplugged the RWAL computer behind the glove box to turn the light off. Somewhere on the internet there are instructions for diagnosing which component of the RWAL system is broken if you narrow it down to that. Did you try unplugging the RWAL computer to see if the light goes out?

tyssniffen

I did, and the light went out. but I want all that connected... I want to figure out why this thing is indicating, not just make it go away.

j_martin

Checkin' in.
You can isolate the fault.
Disconnect the connectors from the vac sensor, the E-brake pedal, and the balancing valve under the master cylinder.
If the light doesn't go out, it's the ABS.
If it does, reconnect the connectors one at a time to find the fault.

I'm betting it's a stuck balancing valve.

Any of the above 3 faults set the brake light. That is sensed by the ABS and sets the ABS light. ABS won't try to function if there's a fault.

bigragu

Edwin, when your RWAL valve showed defective, did it affect your braking at all? Or did you disconnect the ABS module just to rid of the light coming on constantly? Did you end up bypassing the RWAL valve with hydraulic fittings?