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Author Topic: DD3 and air issue  (Read 373 times)
Lin
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1965 MC-5a




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« on: June 27, 2013, 11:10:46 AM »

I have had this happen a couple of times lately.  I air up the bus with the electric compressor, release the brake, depress the pedal, and begin to roll.  However, the brake tell tale light indicating he brakes are still at least partially engaged remains on, and air pressure slowly falls.  I stop, rev the engine, or engage the park brake and rev the engine, which brings the pressure up, and the light goes out.  Does it sound like something is sticking, and what would it be?
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LUKE at US COACH
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« Reply #1 on: June 27, 2013, 12:29:52 PM »

Hi Lin & Folks:

First place to start is right at the pedal.  Next time it happens and the light stays on, pull up the pedal and see if the light goes out.  If so, a little WD-40 on the pedal pin will solve the problem.  If not there, it is a process of elimination starting with the stop lamp switch.

Hope this helps!!!

Happy & SAFE!! Bussin' to All.

LUKE at US COACH
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bevans6
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« Reply #2 on: June 27, 2013, 12:44:03 PM »

The brake lamp tell-tale light comes on when the rear brake lights are on, and is energized by a relay in the rear electrical bay.  The signal from the stop lamp switch, which is an air operated switch located I know not where (I it think is on the front brake line, to be honest, under the driver), goes through the coil of the relay and thence to the stop lamps.  Current through the coil energizes the relay which turns on the lamp.  If you install LED taillights the current through the coil is no longer sufficient to turn on the relay and your stop lamp tell-tale stops working.  All of which is to say that if the lamp is on, it could be the relay sticking on, or the stop lamp switch thinks it has air when it doesn't, or the brake pedal valve is sending air to the switch.   Since you are losing air, I would think the latter.  Not sure why you would be losing air pressure, it should go to activate the brakes if it is turning the brake lights on.

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Vintage race cars -
1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
Lin
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1965 MC-5a




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« Reply #3 on: June 27, 2013, 01:29:36 PM »

Hey Luke, haven't spoken to you in a good while, and it is really good to hear from you.  I will check for the sticking pedal/valve.  Since the incidents have been so quick to overcome, I have not been terribly concerned about it.  Especially since we haven't gone anywhere.  Now as we are getting ready for a trip, I remembered that losing brakes could ruin your day, so I want to dot the tees and cross the i's.

Brian, my thought was that whatever was sticking could even be sending air to the brakes, but not enough to feel.  Since that problem was discovered after a long period of sitting and not while in active use, I was hoping it is just in need of the WD that Luke mentioned or a good long run.  Thanks
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