Brake light on the dash- help needed
Okay guys I have my first cry for help.
Out of all the things that I had to do on my 72 C15 to get it to pass safety inspection I'm down to the final thing and I cannot figure out how to get this brake light off my dashboard. The safety inspector failed me because he said my "master cylinder gasket was swelled" and I have the red light on the dashboard. He told me I needed a new master cylinder to get that light to go off. I replaced the master cylinder with a new one put new rotors and pads and calipers and shoes on the back. I'm a Noob at this so if you have any advice on why that red brake light is on I am all ears because I have to have this thing reinspected Monday morning. Thanks! |
Re: Brake light on the dash- help needed
There is a brake bias valve that has a trip switch built into it...the switch has tripped due to brake fluid loss on one of the circuits...
Follow your brake pipes down from the master cylinder until you find a small cylinder like valve mechanism with brake pipes going in and out.. There will be a wire on a switch that screws into the body of the valve ...remove the wire and the light will go off... BUT...remove the switch and you will hear a click...that's the bias valve re-seating...screw the switch back in and replace the wire.. The light should stay off... :chevy::chevy::chevy: |
Re: Brake light on the dash- help needed
If I unhook that wire, the light does go out, but the guy won't pass me without the wire hooked up.
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Re: Brake light on the dash- help needed
If don’t want to re-set it, remove the bulb in the dash.
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Re: Brake light on the dash- help needed
Like the other guy said, remove the switch from the per portioning valve , press down n hard on the brake pedal and it should reset its self. If not, it’s stuck.
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Re: Brake light on the dash- help needed
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What the switch does is ground the wire that plugs into it and this provides a path to ground for the light. If you disconnect the wire the light should go off unless the wire is shorted to ground in another spot. You could check this easily with a meter.
here is a picture of the valve and the wire that we are talking about. Attachment 1805853 I have read that a really hard stomp on the brakes will reset the bias valve too. I forgot to say. :hi2: :welcome2: to the forum. |
Re: Brake light on the dash- help needed
Consult your service manual. When you bleed your brakes, you're supposed to make a little bracket that bolts on to the master cylinder and depresses the switch. Bleeding your brakes without said bracket doesn't always force the switch hard over to one side but this is what happens when it does.
You just need to recenter the switch. |
Re: Brake light on the dash- help needed
If you know your brakes are working to spec and the only think keeping you from getting your inspection sticker or creds is this guy that will not pass due to the light, pull the wire out of the P-valve and tape the contacts so that you can plug it back in and the light will stay off.
Then go get your inspection pass. Then deal with the light on your own time without this time pressure. It's a 50+ year old piece of hardware that the owner likely knows better than the inspector. Screw him. Do what you have to do to make him see what he needs to see. Hth, -klb |
Re: Brake light on the dash- help needed
Stomp the brake pedal really REALLY hard. The light will go out.
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Re: Brake light on the dash- help needed
While it's running?
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Re: Brake light on the dash- help needed
Remove the wire from the switch
Unscrew the switch and remove it Stomp a couple of times on the brake pedal with the engine running... Replace the switch and connect the wire The light should have gone out... If it still lights after the above process, the wire might be grounded by being pinched perhaps when work was done..or...the switch pin that sticks out of the end of the switch that screws in may be bent of broken off...grab another switch and try again. :chevy::chevy::chevy: |
Re: Brake light on the dash- help needed
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You guys are awesome. |
Re: Brake light on the dash- help needed
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Re: Brake light on the dash- help needed
The small pin that sticks out of the switch drops into a slot machined into the valve itself and locks the valve in the fail over position...
Some switches have the tip of the pin rounded off when manufactured,,,which will allow the pin to be forced back over the lock groove if the pedal is stomped on hard enough... I have always felt that removing the switch takes only a few minutes and allows the valve to center itself again with only a light application of the pedal. There is no chance of any fluid loss... I have had vehicles come to me with the brake dash light stuck on...removing the switch usually show the tip of the plunger snapped off...new switch will fix it every time. These bias switches are a necessary item and should not be omitted or disconnected...they are a quick alert to a failed brake fluid circuit. :chevy::chevy::chevy: |
Re: Brake light on the dash- help needed
Is that switch setup any different in the 4 wheel drum brake setups that have the distribution block instead of proportioning valve?
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Re: Brake light on the dash- help needed
Drum / drum systems still use split circuit designs and I believe most have a bias valve trip system built in...
I just checked my original factory 67 longbed I am working on and it has a proportioning valve like valve immediately under the master cylinder...with a switch built in... I believe the valve in this scenario trips when a hydraulic circuit fails on either front or rear brakes. A true proportioning valve is in a Disk / drum or disk / disk system to limit the pressure applied to the rear system to prevent lockups etc. The alert switch is in these later style systems again to alert of hydraulic system leaks. |
Re: Brake light on the dash- help needed
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