Light is on in dash, removed and cleaned pin switch on E brake what else is there? nothing on MC, possible wire on brake valve under car ? seems I saw one on it, whats the fix?

 

Let's start again. Are you saying that the BRAKE light stays on? If so, there are three ways it lights up. In all cases the lamp sees 12V at all times with the ignition on. The switches close to provide the ground.
First is the lamp test function when the key is in the START position. The ignition switch has a terminal that provides a ground to the lamp.
Second is the e-brake switch. The switch closes if the pedal is in any position other than all the way up.
Third is the differential pressure switch in the distribution block or combo valve. It grounds if there's any difference in pressure from front to back brakes.

Since these wires ground the lamp, any short to ground anywhere in those wires illuminates the lamp. Is the wire to the differential pressure switch even attached, or is the connector grounded somewhere? Is the e-brake pedal fully retracted? Did you try to pull it up? Did you disconnect each of the wires and see if the light goes out?

 

Unless the car is a 67 and earlier, there are only 2 ways, the e-brake or the valve. There is no test function with the key.

 

You're right, sorry about that. I was thinking of the ground for the temp light

 

Sorry 72 D88, cleaned ebrake assembly, and pin switch, thats all ok , check the brake valve next. yes light is on when ig switch is on and running

 

Again, did you pull the e-brake pedal all the way up? Did you disconnect the wire from the pin switch and see if the light was still on?

 

Did you watch the pin release when disengaged? if so then unplug see if it goes out?
Funny i had some trouble with mine the other day not coming on, it was the wire behind the light itself.

 

Unplug the wires 1 at a time at the valve switch and parking brake switch with the key on and see which one makes the light go out.

 

yes as stated previously, had pin switch out and cleaned, lubed up e brake pedal all is fine, going in the dash next,check grounds there and light.There was a flat woven ground cable attached to lower dash panel frame that was cut, by PO or some stereo shop in Lansing that put the stereo in back in 89,need to track that down, believe it may have been for og radio, then back under to check valve switch.

 

Fix the ground first, it could be related and it needs to be fixed anyway. If the light is on after the ground is made good unplug the proportioning valve wire, that switch may be good indicating a leak in the brake system, the wire could be shorted to ground or the switch may be stuck closed and completing the circuit to ground.

Good luck!!!

 

Or you could actually have a brake system problem. Like a leaking rear brake cylinder and a empty reservoir for the rear brakes. Like Joe said it comes on if there is a loss in pressure for one of the brake circuits. Pop the master cylinder cover and take a look.

 

^THIS!!!

No point in trying to diagnosis a warning light that is doing exactly what it’s designed to do! Make sure the brake system works correctly, then make sure the parking brake is fully released. If all that checks out, and the light is still on, then it’s time to start checking wiring.

 

Wait. If there's a brake system problem the fact that the pedal is going to the floor would probably be your first tip-off. So would fluid level problems in the M/C. Check the easy stuff first. The OP still has not confirmed that he has just pulled the e-brake pedal all the way up as a first test. Checking the wiring takes a few minutes.

 

My driver's side front brake line was DRY and the brake warning light only came on if I pressed the brake pedal fairly hard. The master cylinder was full. I assume it was filled by the previous owner. There was definitely a problem but the brake pedal never went to the floor. Not the same issue as above, but the brake pedal may not give a warning if there is a problem.

 

Yes, I actuated the e brake pedal dozens of times while lube and cleaning, and know it has to be up! had to lube it up from setting, had it all working good, release cable out and lubed, pin switch out and cleaned and actuated dozens of times ect. See my newbie post, Saved 72 convert.
Light has been on since I've had it, I replaced all the brake lines and fuel lines as they were rotted, MI car! Have bleed all and its good now, (2 quarts of fluid) only thing left is the valve switch and dash light it self, just looking for guidance as to what is common with these, e brake was my first thought also and checked there first, Switch on valve is oil soaked and nasty so will go there next, along with dash light. Have all other electrical issues fixed ! most minor, all needed bulbs, everything works from ash tray lights to trunk lights . Once I get gas tank fixed were on the road, hopefully before snow! Hasn't seen that since before PO got it in 87, afaik.

 

Totally different failure mode. The light is on all the time in the OP's car. If the differential pressure switch is signalling a loss in pressure in the OP's case, the pedal will be on the floor. Follow the logical failure tree. Analogies to dissimilar symptoms and problems don't really help.

 

If the system is new, and you can’t get fluid to one half of the brake system, and the brake warning light is on, the plunger/switch in the metering block might be stuck.

Give the brake pedal a couple hard jabs, like your trying to shove the brake pedal thru the floor. Alternate bleeding the brakes front to rear. In other words, bleed a rear brake line, then go to the front brake, then back to the rear, etc. The idea is to work the brake light warning switch/plunger enough that it moves freely.


This assumes the master cylinder was properly bleed?

 

Which is very easy to check. Simply unplug the wire at the combo valve. If the light stays on, this isn't the problem.

 

OK,maybe I'm cranky this AM, but why do people want to make this harder than it is? This is a trivially simply circuit and there are exactly three troubleshooting steps to follow.

1. Unplug the wire at the e-brake switch. If the light goes out, that switch is the problem.
2. Unplug the wire at the combo valve/distribution block. If the light goes out, the block is the problem.
3. If neither of these makes the light go out, there is a short to ground in one of those two wires. Find it. The short can be anywhere from either of those two connectors, through the firewall, in the dash harness, or on the printed circuit for the dash.

Those are the ONLY possible causes for the light staying on. The "100 monkeys with 100 typewriters" methods of "troubleshooting" are not the most efficient.

 

That was kinda my point Joe. There may or may not be a brake problem causing the light to stay on. Obviously find the cause of the light first. Parking brake switch, metering block switch, or shorted wire. If not a short, then find what is wrong. But the brake pedal may not be an indicator if there is a problem with the brakes.

 

Joe, cranky?? Impossible!!! Relax, Matlock will be on soon. 😏

I believe we have all said basically the same thing. First set, make sure there is actually a problem (is the parking brake light on BECAUSE the parking brake is set??). If not, next step determine if the light is on because of a faulty parking brake warning issue, or a hydraulic brake issue. The results of that will determine the next step.

I only mentioned the brake bleeding because someone mentioned a new brake system with bone dry brake lines, suggesting a blockage in the lines. Assuming the lines are clear, and the master cylinder is properly bleed and functional, then a stuck brake balance valve in the proportioning valve is a possible cause.

 

What Joe and I are saying is that you don't need to jump through a bunch of hoops or make assumptions. Just unplug each switch and see which one makes the light go out. The direction of the next step in troubleshooting is based on the outcome of which switch makes the light go out or not.

 

That was kind of my point. You don't start diagnosing the check engine light circuits first if your check engine light comes on in your modern car. The op never established that there was no problems with his brakes. Besides it takes less than a minute to check your fluid level.

 

Actually, you do. If you actually read the CSM and follow the diagnosis tree, the first thing it tells you to do when you have a CEL is to verify that the CEL is functioning correctly.

We've wasted WAAAAAY more time talking about this than it takes to follow the three troubleshooting steps. This is starting to turn into a thread worthy of Facebook.

 

Thanks all, just looking for the short cut, Like, "yea the valve switch goes bad, common problem" or wire corrodes on pin switch, ect.
I know other vehicles all have common issues, like my IH Scout has amp gage issues, and fire wall bulkhead electric harness connectors cause problems, or my 6V VW ignition switch has high resistance causing starting issues, being a newbie to Olds, figured I would ask if it was a common thing or not.
One thing I did learn last night was the 16 something bulb is not bright enough to illuminate the PRDL area of the dash pod, put in a 194 bulb, it's perfect!

 

Checking brake function is a subset of Joe's #2 step. This is presuming that there has been no noticeable change to performance.

For what it's worth, if the MC dies and you push past, and barfs fluid out the back onto the booster, the light will not turn on, as that valve switch sees a difference in pressure only. 0 in the front and 0 in the back is no difference. No light. No brakes either.

The problem with this light is that it often finds out about a problem the same time as you do.

 

Pull the emergency brake release lever and pull the e-brake up at the same time. See if it was sticking in the on position.

 

Take your car to a mechanic, ask them to perform the diagnostics 1, 2 & 3 identified in Post #19.

 

Going under to check valve switch next as stated before, brake lines were rotted when I got it, as was light on, so guessing switch is stuck now., E BRAKE IS FINE! first thing I checked.Got to finish putting dash back together then back on hoist

 

I re-read this post three times. I have NOT seen ANYWHERE where you have removed the WIRE from the E-BRAKE pin switch. All I've seen you state multiple times is you cleaned and lubed the pin switch and the assembly. Where in fact have you stated you REMOVED the wire from the PIN SWITCH & the light DID or DID NOT remain illuminated w/ the IGN ON? How does removing and lubing the pin switch demonstrate the wire to the pin switch isn't faulty or the switch isn't faulty?

 

Sorry, just assumed that removing the switch and cleaning it requires disconnecting it, first post. Hard enough to get on your head under the dash as it is, let alone clean contact surface of the switch and the wire terminal while connected, I did do the basic tests. I guess my description of removing and cleaning far exceeds the norm here. I glass beaded the cigar lighter socket inside to remove all the corrosion and clean those wire terminal, did disconnect and remove it from the car, heats much quicker now, don't even smoke! May need to put cell phone charger in there some day!
The lack of any switches on the MC threw me so thought I would inquire, and remembered seeing wires/switch on the valve when replacing brake lines so figured that was the problem after the ebrake check.
I will try to be more thorough in future inquiries, thanks again for every ones input, I'll post results when I get back to the valve, only work on it occasionally.
I suspect this now. as stated it's OG and nasty!

 

Agree, that's a seriously nasty appearing combination valve. I would look to a complete R&R of that combination valve. You'll be far better served in the long run. It will require a thorough bleeding of the brake lines at which time you might consider a good evaluation of your brake lines, etc. But, the combination valve looks nasty. GL

 

The combination valve is described in your CSM & there are many threads/posts regarding same on this site. If you want to increase your understanding on their function, etc - in particular when (if) you elect to change it out, the bleeding tool as described in the video is a great device. GL

 

I believe its ok, new copper nick lines through out, got valve to work and bleed rears ok after some struggle. Problem now is getting gas tank fixed, got to weld in 1 more patch on side then line it,hopefully liner will take care of whats missed, bottom is fine on tank,not one pin hole or inside rust! just the side seems and some pin holes on top where the 50 year old dirt sets, so I can drive and test brakes!

Side of tank rots from dirt setting in upward bent flange.

This side done now and not leaking, other side next.

 

Brake light fixed!!! rolled it out of the barn today to let run awhile and warm up. gave it a little power brake both forward and rev. light went out!, must have been just enough shock to brake system it put that switch back in its place... thinking possible bulb burning out, applied the e brake, light came back on, no light when ig. turned on though, should it? Oil and Gen come on ok.
Maybe another bleed.
Like any old car, got to keep it running and driving, they work better that way, worst thing you can do is let them set, IMHO.