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Brake Indicator Light-What does it mean?


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29 replies to this topic

#1 2-baru-family

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Posted 21 September 2005 - 02:48 PM

My '98 Legacy sedan has 48K miles and change. This morning, the dash's "BRAKE" indicator light is illuminated. Fluid levels are good, no low pads since I checked a month ago, no change in pull under braking. I'm stumped, help me out!:banghead:

What could this mean? Do I need to make an expensive trip to the dealer for wallet removal? Naw, my buddies at the USMB could help me figure this out so I can get to the bottom of it. :D

Thanks in advance!

#2 Dickensheets

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Posted 21 September 2005 - 03:08 PM

What does the owner's manual say about this light?

#3 Setright

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Posted 21 September 2005 - 03:49 PM

Permanently on, or only when you press the brake pedal? The car might just be trying to tell you that one of the brake bulbs is burned out.

If your brake fluid is above the minimum level, the brake fluid warning light shouldn't come on - unless the wire is broken or disconnected.

#4 unverviking

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Posted 21 September 2005 - 05:36 PM

Just had this with my GMC, typically the BRAKE light indicates either the parking brake is applied (Maybe a little bit, enough to hit the light) OR a failure within the traditional braking system.

In the case of my GMC, my pedal was squishy and took it until the floor to stop the truck. Luckily it's a stick, so I was able to downshift it to stop it... They found today I have a rotted out line and once replaced, it will need to be bled and then the light should be out...

I would be wary and pay attention to ANY brake irregularities...

Keep "us" posted...

#5 tcspeer

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Posted 21 September 2005 - 05:42 PM

Have you or anyone else been in the master cyclinder tank? If so you may have the little float device stuck at the bottom of tank. Making it read as though you have low brake fluid.

#6 ferret

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Posted 21 September 2005 - 06:18 PM

Open the brake fluid, add a little and push the 'bladder' back into the cap.
Had this on my 82GL, 85GL wagon, 90 Legacy wagon and 02 Forester. The Bladder goes down as the fluid fills the caliper when the pads wear. The bladder keeps the air out of the brake system. Only problem is as the fluid gets low, it also pushes down the float which trips the reed switch and illuminates the Brake light on the dash board.
This is a Subaru anamolie.....and one they haven't done anything about in over 20 yrs of my experience with them.

#7 nipper

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Posted 21 September 2005 - 06:26 PM

Actually the theory is you still have three switches that set off the dash light. First one is parking brake. Second is in the resevoir, which is used to tell you ist time for new brake pads (assuming no one has toped it off), and the third one is the brake pressure switch, which comes on when you press the pedal and something is blown (caliper wheel cylinder etc). iIdont think they use it as a lamp function test. Unfortunitly some mfgs have droped the brake pressure switch and just use the level switch, i dont know what sooby has done off hand.

This is not a light to ignore. To rule out the level switch, just unplug it from the harness and it should go out. Next check the hand brake switch. If that doesnt work, inspect the brake system.
This light is too important to ignore.

Joe

#8 1 Lucky Texan

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Posted 21 September 2005 - 11:33 PM

My daughter's Nissan does it too. Most likely to happen after an unusually cool night if the fluid level is marginal.

Could this also be an indication the brake fluid needs to be flushed out/replaced? maybe too much moisture in the system makes it contract more?

i dunno

#9 Cougar

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Posted 22 September 2005 - 12:04 AM

Just to be aware of, these warning lights are sometimes used in the alternator circuit and will light up if there is a problem with it. I'm not sure if this is the case with this light or not though.

#10 nipper

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Posted 22 September 2005 - 12:35 AM

OO yes I forgot about that. It was one of those things I never understood, why the failure of a diode would cause that to happen. In fact a failing altenator can cause all sorts of weirdness with the idiot lights. Odd now that I think about it, every time I had an Alt go bad the Alt light never came on.:-\


Joe

#11 Cougar

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Posted 22 September 2005 - 01:02 AM

Some of the warning lights are in series with the alternator exciter circuit so when the alternator has a problem it effects the lights.

OO yes I forgot about that. It was one of those things I never understood, why the failure of a diode would cause that to happen. In fact a failing altenator can cause all sorts of weirdness with the idiot lights. Odd now that I think about it, every time I had an Alt go bad the Alt light never came on.:-\


Joe



#12 ferret

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Posted 22 September 2005 - 06:06 AM

Sorry, not on this model. This is a simple circuit with 2 switches and 1 bulb. Handbrake switch and low fluid reed switch. No diodes, connecting circuits or 3rd switch, like GM used, to the proportioning valve.

On later models with DRL, there is a single diode added to isolate and input to the DRL module. This is the trigger used to turn off DRL's when the handbrake is engaged.

#13 1 Lucky Texan

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Posted 22 September 2005 - 07:51 AM

Sorry, not on this model. This is a simple circuit with 2 switches and 1 bulb. Handbrake switch and low fluid reed switch. No diodes, connecting circuits or 3rd switch, like GM used, to the proportioning valve.

On later models with DRL, there is a single diode added to isolate and input to the DRL module. This is the trigger used to turn off DRL's when the handbrake is engaged.


I think they were refering to the 'diode trio' inside the alt. I HAVE seen one car (an Oldsmobile we had)that the alt light was on VERY dimly and it was the alt that was bad. But other cars, it was some general weirdness as already mentioned that ended up being caused by a bad alt. Maybe instead of a voltmeter there needs to be a 'ripple' detector to let us know when the alt diodes go bad.

I dunno

#14 nipper

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Posted 22 September 2005 - 08:44 AM

Yes i meant the diode tiro, which is no longer a trio. Ive seen as many as 12 diodes on that bridge now, in order to smooth out the electrical peaks for the puters...


Joe

#15 2-baru-family

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Posted 22 September 2005 - 09:16 AM

Thanks to all for your helpful replies. Love this board!


I found another thread that suggest re-seating the cap if the fluid levels were in the good range. I will try the check the bladder as well before looking at other diagnostics. Weather is getting cool at night here and, as we are high desert, things heat up during the day.

Thanks again!

#16 shortlid

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Posted 18 October 2005 - 08:28 AM

Same thing happened to my Mom's '03 GT Legacy sedan when heading too work today. She called me from down the road. She said the red BRAKE idiot light came on. She tried releasing the e-brake a few times with no change. I had her check the brake res. and the fluid level was fine. When she shut off and re started the car the brake idiot light went out and stayed out?? Only thing I can think of is stuck fluid level sensor in brake res.?

#17 Cougar

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Posted 18 October 2005 - 10:29 AM

I'm not sure if this is still a problem or not since this is an older thread but after looking at some wiring diagrams I noticed there is a diode tied between the parking brake/fluid level and charging indicator lights. The diode is on the low side of each of the lights with the anode tied to the parking light side. I guess if the charge indicator light is not making contact or blown out then a path through the parking light may be made to the alternator circuit. Make sure the charge indicator light is working when you switch the key to ON to test the dash lights.

#18 shortlid

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Posted 18 October 2005 - 10:33 AM

OK, so it could be a charging system problem or maybe she left a light on and it drained the battery??

#19 frag

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Posted 18 October 2005 - 11:11 AM

On sure test: with the parking brake off, if the warning light is on AND the driving lights are not, it's the parking brake lever switch that's faulty. The parking brake switch monitors the
day time driving lights.

#20 shortlid

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Posted 18 October 2005 - 11:54 AM

Cool, I never thought of that I will have her check it. Thanks

#21 Cougar

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Posted 18 October 2005 - 12:12 PM

I don't think that there will be a problem with the 'brake' warning light turning on unless the 'charge' light has a connection problem or if there is an abnormal situation in the alternator and then both lights would be on.

OK, so it could be a charging system problem or maybe she left a light on and it drained the battery??



#22 Tiny Clark

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Posted 18 October 2005 - 12:22 PM

Make sure the rubber bellows that is attached to the brake fluid cap is not extended outwards. If so, it will push the float down to energize the fluid level switch even tho plenty of fluid is in there.

It should be pushed back against the cap.

#23 Cougar

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Posted 18 October 2005 - 12:47 PM

Good tip TC.

#24 nipper

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Posted 18 October 2005 - 02:02 PM

Yes oddly on a number of cars that I have, more so Japanese, the barke light would come on way before the battery light would come on with a failing altnator. When it got real bad all the idiot lights would come on... except the battery light.
It may have to do with the type of failure it was inside the altenator. I think the battery light comes on if its a bad regulator, not a bad diode.

nipper



#25 zyewdall

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Posted 18 October 2005 - 02:25 PM

Yes oddly on a number of cars that I have, more so Japanese, the barke light would come on way before the battery light would come on with a failing altnator. When it got real bad all the idiot lights would come on... except the battery light.
It may have to do with the type of failure it was inside the altenator. I think the battery light comes on if its a bad regulator, not a bad diode.

nipper


Yeah, in my '85 subaru the alternator failed, and the battery voltage got down to about 8 volts (still running, though a bit rough). The battery light never came on, but all the other idiot lights did (Brake, Oil pressure, EGR). If only the one brake light is coming on though, it's probably not the alternator. A quick voltage check with a multimeter can rule it out though.




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