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Brake Light on dash
Drove the bus today–first time in 2 weeks. The ‘Brake’ light on the Silver Leaf was on when I started out and after a few rapid brake applications it remained on. This light IS NOT THE PARKING BRAKE LIGHT. Usually a stab on the brake and the light goes out. Not today. I drove about 10 miles in this condition watching the individual wheel temps on the ‘Smart Tire’.
84 degrees OAT and the wheels reached 98 degrees. With this info I assume the brakes are not dragging. How do I fix my problem?
Thanks, Larry
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14 Replies
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Are the brake lights actually on, or just the light in the dash? That makes a difference on what to check.
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Brake light (indicating the brake lights are really on) or ABS light indicating the ABS system has a fault?
Does the Cruise Control work?
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Mark, the brake lights are on when I turn the ignition switch on.
Jon, not sure I follow your questions, the ABS light is Not on, just the dash Brake light and now, thanks to Mark, I find that the external brake lights are also on.
Larry
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Under the place where your feet go in the steer compartment is the bottom side of your brake treadle.
There should be two pressure switches, one with a red air line the other with a green. You can check to see which of the two is closed. If I were to guess I would start there with the assumption one of the brake light switches is malfuncting (that is a highly technical term).
I would guess you cruise is not working also.
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Jon, I think I have located the valves and the pressure switches, but unable to determine if the switches are open or closed. There is a panel with some aux air lines and my bus alarm system mounted on it in front of the pressure switches so, it is one of those “stand on your head deals”
To confirm I am looking at the pressure switches, are they a 21/2 around and maybe an inch or so thick with 2 wires mounted to them? How would I know their open or closed position?
Thanks
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I have just checked the continuity between the studs on the press.switches. Post to ground has continuity and post to post on both switches have continuity. That would seem thar both switches are closed. I did this check with parking brake applied and off.
So, something [pressure] is keeping the switches closed allowing the brake lights to stay on. I doubt that both switches failed close at the same time. Is this a fair assumption?
The bus can’t be driven until Monday so info on cruise control will not be available until then.
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You would have to go to the Prevost electric diagrams for your coach to verify if the brake pressure switches are functioning as intended. I agree that it is doubtful both failed simultaneously.
With the coach turned off, and the parking brake “on” there should be no pressure on the brake side of the primary or secondary brake systems so I would expect the pressure switches to be open but that is a guess not knowing if they are normally open or closed. I believe the brake lights or at least a portion of that circuit is part of the disconnect for the cruise control which is why I asked if that is functioning.
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Thanks Jon, I’ll keep working at it and post what I find.
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Larry,
I am not sure I made it clear when I said there was no pressure in the primary or secondary brake systems when the bus is parked. There will be pressure to the input side of the brake treadle, but I believe the switch side should have zero pressure. There will be no pressure to any of the emergency or service brakes at the brake chambers.
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OK, thanks that is what I took from your last.
Are the switches I described the correct ones? If they are the two switches shown on my Prevost drawings, they should be ‘open’ until the brake treadle is pushed. The drawing also show that the cruise control will not engage with these switches ‘closed’
I looked for other circuitry that may need to be activated to allow the light to remain ‘on’ and found none.
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I believe you got it. Yes those are the switches and if I understood a previous post you indicated both are closed. Either both failed, or you have air pressure not releasing downstream from the treadle or just one switch remains closed. All easy to check.
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Now, The Rest of The Story as Paul Harvy used to say, I drove the bus this AM and tried the cruise control–it didn’t work.
The problem was a failed switch —the DECEL switch—for the cruise control. It had failed closed allowing power to the brake lights. Replace the switch and all is well
Thanks for your help Mark and Jon. It would have taken a while before I worked my way to the cruise contol if Jon had not brought it up.
Thanks again.
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Glad it was a relatively easy fix. Did you buy the switch from Prevost?
My DECEL switch may be going bad. I have had to hit it twice on several occasions lately.The first couple of times I thought that I did not hit it good the first time.
DKO
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My switches are the damn ‘Sun Mulon’ switches that CC used. I have a few on hand for just this sort of thing.
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