Brake light came on today....

[Blue90]

it's not the first time it's been on, but usually it blinks a certin amount of times and i guess by that you can usually tell what the problem is. But this time its staying solid. Any ideas of what could be causing this? Or possibly how to reset it?

It's on my 1990 K5

 

[chevyridinhigh79]

check your brake fluid, if its low on fluid it will stay lit. i suppose your talking about the lgiht that comes on when you apply the emergency brake.

 

[MNorby]

check wire on your m/c or prop valve I've seen them fall off or get burnt on exhaust and short and turn light on too.

 

[dyeager535]

Need to figure out if it's an ABS code or a brake circuit failure indicator.

No idea if the ABS always flashes, or if it will come on solid for some faults.

As mentioned, check the single wire (tan?) that runs to the proportioning valve for a problem. If it looks ok, disconnect it and see if the light goes off.

When my master cylinder went, my brake light started coming on.

 

[dremu]

1990-91 RV trucks (i.e. Burbs, Blazers, and crewcabs) have that hideous rear-wheel-only ABS, and it will blink the brake light with a code when it's angry. (Dorian, I believe from the days I owned a '90 truck that the ABS only ever blinks.)

If the light is on solid, that indicates a major pressure difference between the front and rear circuits.

This can be caused by low fluid. After checking the fluid level, you can reset the light on the combo valve ... follow the brake lines from the master cylinder down to the crossmember (under the fan blades, basically, and should be on the back of the crossmember.) There's a rubber button (IIRC on the left, i.e. driver's side) -- push it in, may take some force. (Actually the rubber is just a cover for a metal slide.)

The pressure difference can also be caused by a leak or air in the system, so just putting fluid in and resetting it isn't a guaranteed fix.

I'd check fluid and reset the thing, but if the light pops on again, you're in for some hydraulic work. Check the rubber lines at the calipers in front and at the read axle in back, then look for leaks on the calipers or on the wheel cylinders in back... and as Dorian just said, a leaky master. At the very least bleed the system, and since you're gonna be looking at the various hydraulic components while bleeding anyway, checking them is easy.

As mentioned, you can check the wire from the combo valve -- should only be one, tan or yellow, IIRC (my trucks are old and everything is faded ) and make sure it's connected to the valve and is intact up into the dash.

-- A

 

[dyeager535]

You can also disconnect the ABS unit can't you, just to make diagnosis easier?

I know there are a few people who have had to manually reset the prop. valve as mentioned, but in my experience (not extensive, maybe only 10-15 bleeding sessions on various GM vehicles with this setup) I've never had to reset it manually. According to GM its SUPPOSED to reset itself when the system is working correctly. Again, I know it is possible to require manual reset.

I'm wondering if the earlier manuals are the ones that talk about the "manual" prop. valve reset(?)...I don't think it's in my '90 manual. Probably just says replace.

 

[Blue90]

Okay so i checked and unplugged the tan wire, that did nothing. The fluid level is fine. When i looked for that button dremu talked about that is on the cross member i noticed that it's probably behind my steering box brace.....so I'll take that of and see what i can see. I also think i should mention this cause it's probably related and well i probably should have said it earlier but. I re wired my trailer plug on it yesterday and the brake light came on after i tested it. All the lights on the trailer came on and worked great....so i dunno if that helps at all.

 

[dyeager535]

I may screw this up (backwards) but if you removed the wire from the prop. valve, then the light should go off it's a braking issue.

The only other trigger for the brake light is the switch on the ebrake itself. I believe disconnecting it should kill the light.

E-brake wiring is seperate of the turn/signal brake light stuff, so they shouldn't be related unless you started tapping into wiring in the dash.

 

[Blue90]

na it's defiantly not the e brake cause when i put that down the light gets brighter and when i take it off it gets dimmer. but i did get er reset and it has not come back on yet. Yahoo! Thanks for the help guys.