Brake dash indicator light
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Elder User
Joined: Jul 2006
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From: Near the ocean
Brake dash indicator light
93 F250
When I sit at a traffic light with my foot on the brake pedal, after about a minute, my red "brake" indicator light comes on. As soon as I release the pedal, the light goes out. I suspect the balance switch for the front/rear brakes is not centered. Can someone tell me where it is located? Or can I have someone press the brake and loosen one or other line coming out of the master cylinder
When I sit at a traffic light with my foot on the brake pedal, after about a minute, my red "brake" indicator light comes on. As soon as I release the pedal, the light goes out. I suspect the balance switch for the front/rear brakes is not centered. Can someone tell me where it is located? Or can I have someone press the brake and loosen one or other line coming out of the master cylinder
Posting Guru
Joined: May 2015
Posts: 2,036
Likes: 5
93 F250
When I sit at a traffic light with my foot on the brake pedal, after about a minute, my red "brake" indicator light comes on. As soon as I release the pedal, the light goes out. I suspect the balance switch for the front/rear brakes is not centered. Can someone tell me where it is located? Or can I have someone press the brake and loosen one or other line coming out of the master cylinder
When I sit at a traffic light with my foot on the brake pedal, after about a minute, my red "brake" indicator light comes on. As soon as I release the pedal, the light goes out. I suspect the balance switch for the front/rear brakes is not centered. Can someone tell me where it is located? Or can I have someone press the brake and loosen one or other line coming out of the master cylinder
Scope Wizard
Joined: May 2019
Posts: 6,530
Likes: 25
on the 93 there are 3 ways to trigger that Brake light Normally .... low fluid sensor under the Master Cylinder Reservoir, Low Vacuum sensor located near the Driver's side battery, and the parking brake switch.
Ok 4 ways for a normal trigger .. it should also turn on and do a Bulb Test when the Ignition switch is in the Start Position,
as suggested by DOC it is probably a Low Vacuum Warning.
there is no proportional valve on this truck, that is all handled by the Master Cylinder and the RABS any RABS failure sets the ABS Lamp not the Brake warn Lamp however the RABS computer does watch the Brake Warn Lamp signal.
Ok 4 ways for a normal trigger .. it should also turn on and do a Bulb Test when the Ignition switch is in the Start Position,
as suggested by DOC it is probably a Low Vacuum Warning.
there is no proportional valve on this truck, that is all handled by the Master Cylinder and the RABS any RABS failure sets the ABS Lamp not the Brake warn Lamp however the RABS computer does watch the Brake Warn Lamp signal.
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Elder User
Joined: Jul 2006
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From: Near the ocean
Thank you DOC and lonewolf for your input. I will check it out and let you know.
I posted my truck for sale. Surprised you had no comment lonewolf. You have spent so much research time on it, it's almost a part of you
I posted my truck for sale. Surprised you had no comment lonewolf. You have spent so much research time on it, it's almost a part of you
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Elder User
Joined: Jul 2006
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From: Near the ocean
Would you please reply to my other post concerning my fuel problem?
Thanks
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Scope Wizard
Joined: May 2019
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I really thought everything was pretty much covered.....
and BTW you might not have a Cracked Check Valve on the Booster but I have seen that and it causes low Vacuum....
More than likely either the Pod on the Vacuum pump is weak or maybe the Brake booster is leaking .... BUT as long as you don't have low Fluid and the Brakes work fine don't worry too much about it.
BUT you can always put your Vacuum Gauge on that Vacuum Manifold mounted on the driver's side fender well and see what is happening... you know it could be you are loosing Vacuum from one of the HVAC lines too.
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Thread Starter
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Elder User
Joined: Jul 2006
Posts: 621
Likes: 1
From: Near the ocean
on the 93 there are 3 ways to trigger that Brake light Normally .... low fluid sensor under the Master Cylinder Reservoir, Low Vacuum sensor located near the Driver's side battery, and the parking brake switch.
Ok 4 ways for a normal trigger .. it should also turn on and do a Bulb Test when the Ignition switch is in the Start Position,
as suggested by DOC it is probably a Low Vacuum Warning.
there is no proportional valve on this truck, that is all handled by the Master Cylinder and the RABS any RABS failure sets the ABS Lamp not the Brake warn Lamp however the RABS computer does watch the Brake Warn Lamp signal.
Ok 4 ways for a normal trigger .. it should also turn on and do a Bulb Test when the Ignition switch is in the Start Position,
as suggested by DOC it is probably a Low Vacuum Warning.
there is no proportional valve on this truck, that is all handled by the Master Cylinder and the RABS any RABS failure sets the ABS Lamp not the Brake warn Lamp however the RABS computer does watch the Brake Warn Lamp signal.
I sure wish my problem with the IP was as simple
Thanks again lonewolf
5th Wheeling
Joined: Mar 2020
Posts: 49
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I had my brake light come on a few months back. I would depress the pedal once, and then if I needed to brake again in short succession the pedal would be solid and the light would come on. Ended up being my Vac Pump. Easy enough to swap out and I didn't even have to bug Lonewolf 
Have you noticed any change in your brakes or is it simply the light? If you have vac issues I would suspect you would be loosing some pressure on the booster. If it's just the light I would suspect the sensor. Just my 2 cents as a novice. Good luck!
Have you noticed any change in your brakes or is it simply the light? If you have vac issues I would suspect you would be loosing some pressure on the booster. If it's just the light I would suspect the sensor. Just my 2 cents as a novice. Good luck!
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