anyone had park brake light and buzzer stay on?

[racing4funn]

Brake releases and truck is fine but the light and buzzer is hard to ignore. Air pressure is good on both tanks.

Anyone seen this?

 

[phil2968]

Dual brakes we can assume from the light? Check the switch at the parking brake handle to make sure it is not stuck.
Edit: just noticed this was in the 5 ton forum, doh!
Never mind, I know nothing!

 

[Artisan]

What truck?
What air pressure is it at that you call good and when?
What happens when you do a DMV brake test?

 

[TexAndy]

I think he's talking about the light/buzzer controlled by failsafe warning control module.

If so, its almost guaranteed to be a bad failsafe warning control module. They're notorious.

 

[Rifleman]

Look up your model of truck using the correct TM's for that truck and trouble shoot your problem. Now if it's a M939 series of truck you will find a complete trouble shooting guide in the TM's to help you pin point your problem. I used the TM's to help solve the exact same problem your having in a M925. I hope this helps

 

[racing4funn]

it is a M939. pressure is 90 to 120. doesn't matter where is pressure is. The dash light/buzzer wont ever go out.. funny that the pitch of buzzer changes very slightly when I take the park brake off.

 

[juanprado]

Fail safe gets input from air tank low pressure switch and parking brake switch.

 

[GHall]

I had rats chew through the wire for the parking brake going under the cab on the drivers side of my M932A1. Had the same effect.

 

[racing4funn]

Fail safe gets input from air tank low pressure switch and parking brake switch.

are you saying look towards the fail safe system?

 

[Artisan]

If you do not get some kind of command of the TM's (Technical manuals) you will
be seriously handi capped for life working on your truck. Sure guys will help
but the TM teaches you so much more. I have an IPAD w/ all the TM's loaded
on it and it is in the truck anytime I drive it in case I break. They CAN get
you up and running instead of calling a tow=EXPENSIVE!

I have been thru the exercise you are doing and I could write 3 pages of
how to's but you will be much better served to read the TM's.

They are free and available in the TM section here.

There are 2 low air "switches" one on the primary and one on the secondary
air tanks, they have a ground (55 wire?) , then a wire up to
the FWCM. I pulled my ground and cleaned it and replaced both air switches and
tested the wires just like the TM says to do and then I replaced
the FWCM and now mine works but if you do not know how it
does what it does, again your handicapped. That is a full blown air brake
truck. A Commercial Class B license is required most everywhere
you drive it. If you are worth a few dollars you should RUN and get
a CLASS B so incase you wreck you do not get sued and loose over that
little technicality. Getting a Class B will teach you a LOT about your
air brake system as well. You will thank me if you go to a professional
truck driving school and learn what is required knowledge to legally
drive these things on most roads per Federal Law ....

The TM's take you on a step by step how to for repairs.

There is an OPERATORS MANUAL TM xxxxx-10 I think, it tells you a lot
but no big time how to repairs.

There are 3 volumns of PARTS
There are 4 volumns of Maintenance
There are 5 Volumns of Field maintenance.

and more, the above is about 10,000 pages. Yep!

It is a daunting task, just start and try to remember what is where
for future use.


Here is a gentle nudge CLICK HERE

The M939 is a Series of trucks

Look at the passenger side dashboard and tell us what model you have!

M923?
M923A1?
M923A2?
M925?
M925A1?
M925A2?
M936?
M936A1?
etc te al

 

[racing4funn]

Artisan I hear yall. Ive been wrenching on car my who life and know ever inch of some but I learn much better hands on and the size of those book are daunting (I have the set in actual paper and binder). Plus with two babies under two is killing me right now. Im going to start flipping threw them tonight. Can anyone direct me and what set of TMs to even look in? Im sure there is a flow to the madness that Ive not pickup on yet.

 

[racing4funn]

found it
TM 9-2320-272-23-1t
page111

I read threw it and it says to check the wire and check the switch and if all is ok and problem is still there then contact a supervisor (what is his phone number?)

problem might be a side affect of description on page 110.. I will trouble shoot what little it gives.. Maybe I will get lucky

 

[wvandenb01]

I'm having the same trouble, low air and buzzer with 120psi. Shuts off occasionally then starts again. Thanks everyone for the troubleshooting tips.

 

[tbar123]

I have a M923 1984', and am having the same problem. I have looked through all the TM's and the closest I could get was." Spring Brake Warning light inoperative with Spring Brake override engaged". Didn't help. Wrong problem.

 

[twinturb089]

Most of the time,One of the two low pressure switches on the primary or secondary tanks are stuck or bad. start your truck,let air pressure build to 90-120 lbs and unplug 1 switch and use a jumper wire to complete the circuit.see if buzzer or/and light are off.Repeat with second switch. sometimes the switches can be tapped on and are just stuck.Replace switch as needed.I have had over 30 923's the past year and have only had switches bad when the light/buzzer does not go off. when the lights do not go on and buzzer does not work.Then the failsafe module is probably bad.The plastic ones i have seen fail more than the metal ones.