Brakelights Stuck On!

brianzero · May 04, 2017, 04:59:26 PM

Hi All,

My MCI-9 brakelights are stuck in the "on" position when the bus is running. I know there is supposed to be a switch under the floor beneath the brake pedal, but I couldn't find it. Any thoughts on this one?

PorchPeople · May 04, 2017, 05:04:24 PM

They will normally be on until the parking brake is released. If they still stay on I would check the switch. It may be stuck closed.

brianzero · May 04, 2017, 05:17:57 PM

Quote from: PorchPeople on May 04, 2017, 05:04:24 PM
They will normally be on until the parking brake is released. If they still stay on I would check the switch. It may be stuck closed.

Which switch is that? One connected to the parking brake assembly?

bigred · May 04, 2017, 05:33:05 PM

Do you have a floormat?? My Prevost is so sensitive that if the rubber floor mat gets under the back (heel)of the brake pedal,it is enough to keep the BL on.

brianzero · May 04, 2017, 05:40:14 PM

No floor mat, but interesting issue you have. This is definitely a switch or a sensor fault 'somewhere' buried in the system.

dj · May 04, 2017, 06:19:23 PM

I had the same problem on my 102A3 if the brake lights don't go off when your release the brakes there is a pressure switch in the forward spare tire well you can access it from under the drivers side (the door for the window washer) there is a large valve mounted on the back wall about 6" diameter and about 10" tall the pressure switch is mounted on a line coming off the front near the top....hope this helps

brianzero · May 04, 2017, 06:24:42 PM

Thanks DJ. Maybe the MCI-9 has the same valve configuration as the 102A3. Do you have to move the space tire to get access to the valve? Or can I slip around it without removing the spare tire? I killed my back last time I had to move that spare tire.

sledhead · May 05, 2017, 04:28:53 AM

the one on my 1023c looked like this one and you may be able to get to it from the door under the driver side window

https://www.anythingtruck.com/product/070-BE13250.html

dave

PorchPeople · May 05, 2017, 09:31:26 AM

I couldn't tell you exactly where the switch is as I'm not familiar with that coach. It's likely in the spare tire compartment or tool compartment. If you have a wiring diagram/ maintenance manual you can locate it by the numbers on the wires ( MCI got something right!). Alternatively you can trace it from the application valve by following the air lines. Once identified, you can bench test the switch (ohm meter + air nozzle) or just connect/ disconnect the leads to verify its stuck closed. They are a common truck part, and inexpensive. While your in the hole check for leaks! Also be sure to drain your tanks regularly. I've found oil all the way to the wiper valves due to poor maintenance practices. It will surely destroy switches, quick release valves, diaphragms, etc.
Ps I believe that switch is normally open. Make sure you replace with the right type or the lights will work backwards! You can guess how I figured that one out.

buswarrior · May 05, 2017, 10:42:30 AM

The coach may have both types under there, depends where it is plumbed in.

Have you got the maintenance and parts manuals?

there will be one or two for the service brakes, and one for the parking brakes.

You didn't clarify, under what condition are the brake lights lit?

As earlier poster noted, the brake lights stay on by design, with the ignition on and parking brake applied.

happy coaching!
buswarrior

brianzero · May 05, 2017, 10:48:30 AM

Quote from: buswarrior on May 05, 2017, 10:42:30 AM
The coach may have both types under there, depends where it is plumbed in.

Have you got the maintenance and parts manuals?

there will be one or two for the service brakes, and one for the parking brakes.

You didn't clarify, under what condition are the brake lights lit?

As earlier poster noted, the brake lights stay on by design, with the ignition on and parking brake applied.

happy coaching!
buswarrior

The brakes lights are on constantly, when the bus is running, even if the pedal isnt depressed. My suspicion is that moisture killed the sensor, due to infrequent air tank draining.

luvrbus · May 05, 2017, 03:52:14 PM

At the parking brake valve there should be a normally closed air controlled switch with 2 or 3 wires to turn the lights on regardless of air pressure when the master switch is on.That is where I would start you release the parking brakes with the PV it opens that switch and fwiw some Bendix and Haldex PV valves have the switch integrated into PV (parking valve)

good luck

dj · May 05, 2017, 06:26:40 PM

standing outside the bus...drivers side, forward of the steer tire , under the drivers window and under the electrical panel there is a hinged panel, open that and get down low and look up to that back wall, you should see the valve...

buswarrior · May 06, 2017, 08:26:54 AM

brianzero, I'm looking for you to say: "The brake lights stay on, with the parking brake released, and the coach rolling, with no brake pedal applied."

Your bus, by design, in general, applies the brake lights two ways, with the parking brake, and with the brake pedal.

Your descriptions only say the bus is running, you aren't describing what the parking brake is doing while it is running?
If it is parked, then the brake lights are supposed to be on.

And specifically, the low air warning switches, the brake light switches, and there may be duplicates built into the system mandated by safety regulations, these can all appear externally to be the same, depending on the air switch's manufacturer and vintage. Some switches make contact in the presence of a certain air pressure, some make contact in the absence of a certain air pressure.

Stuff changes over 60 years of "modern coaching", both the stuff installed, the manufacturers, consolidation, bankruptcies, re-branding...

Counterfeit parts is a whole 'nuther volume of danger to the unknowing busnut with no commercial background.

Previous owners and their mechanics are famous for slapping in "work-arounds" with the parts available lying around vs replacing with the "proper" parts.

This can be a big problem, as "functionality" doesn't necessarily mean it will work as designed or intended under all conditions. There are some bus conversions out there that may not stop as designed if they suffer an air emergency, due to "work-arounds" that "functioned"

That is why you will read so often in the GOOD forums, (not social media) that the manufacturer's maintenance books are a must, so that a busnut may have a fighting chance against the previous owners...

The joys and curses of old buses?

Keep going! We're behind you!

happy coaching!
buswarrior.

brianzero · May 06, 2017, 08:58:53 AM

Thanks buswarrior. The brakelights are stuck on while parked with the parking brake on or off, while driving, while the air tanks are full, while the brake pedal is depressed, and released (basically all conditions). I'm going to dig out and replace that air break pressure sensor, and hopefully that'll fix it. I'm going to order one from Luke, so it should be high quality stuff.