Freightliner Cascadia: Park Brake Air Low, Brakes May Drag

[Mike]

I started getting this warning on my truck this week: "Park Brake Air Low, Brakes may Drag"

I pay pretty close attention to everything with the truck, so I noticed this immediately when things didn't seem right. I was seeing this warning with air pressure was close to 90psi. Never seen it their before. Within a couple days, I was seeing it near 100psi, and by the time I got home it was coming on at times even above 100psi.

I double checked my air system to make sure it wasn't leaking down via the gauges. Looked and listened all around the tractor and trailer, nothing was leaking anywhere.

Turns out, Freightliner has a switch specifically for this warning. as if the low air pressure warning isn't enough. This is brought to you straight from the department of redundancy department. One switch could have handled both systems just fine.

The switch is named: "pressure switch, brake drag warning". See? The switch has one purpose in life.

The other brake pressure switch has been replaced twice already. When that one fails, cruise control doesn't work and brake light will stick either on or off.

Why do they fail? air system contamination. Does draining your tanks help? Probably. Does it prevent the switches from failing? Obviously not because I perform this function regularly. And yes, I replace the air dryer cartridge regularly as well.

As you can see in the video, (or hear), the parts guys know this part very well as they sell them all the time.

My freightliner warranty covers the switch, but my patience on waiting around forces me to just fix simple things like this rather than risking the truck being down for more than a day. I could probably have gotten it taken care of in one day, but for less than an hour of work, just made sense to do it myself. And it made for a good video opportunity.

 

[Mike]

The short version

 

[Duck]

Can't you just bypass or disconnect that switch? You don't need it if you've got the regular buzzer and gauges.

 

[Mike]

Can't you just bypass or disconnect that switch? You don't need it if you've got the regular buzzer and gauges.

You definitely could. It's a simple two wire switch so just a matter of knowing if it is normally open or normally closed. Which is it? I don't know, but just a matter of checking it out with a DVOM.

That said, I'm trading the truck while it is still under warranty and not sure where the legal issues would lie in regards to bypassing something like that. I've already bypassed the seat belt wiring where I don't have to hear that nonsense when taking the seat belt off. by the way, that required a closed circuit created by the seat belt being buckled and completing the circuit. So, those wires are wired together and stuck under the extra flooring I put in the truck to protect the factory flooring from the psycho dog that likes to chew on things.

 

[Duck]

You definitely could. It's a simple two wire switch so just a matter of knowing if it is normally open or normally closed. Which is it? I don't know, but just a matter of checking it out with a DVOM.

That said, I'm trading the truck while it is still under warranty and not sure where the legal issues would lie in regards to bypassing something like that. I've already bypassed the seat belt wiring where I don't have to hear that nonsense when taking the seat belt off. by the way, that required a closed circuit created by the seat belt being buckled and completing the circuit. So, those wires are wired together and stuck under the extra flooring I put in the truck to protect the factory flooring from the psycho dog that likes to chew on things.

I had a seat switch on a riding mower that was impossible to bypass.

Just two wires. Open circuit, mower won't get spark. Closed circuit, mower won't start. Plug the connector back on the switch and it fires right up.

 

[Mike]

I had a seat switch on a riding mower that was impossible to bypass.

Just two wires. Open circuit, mower won't get spark. Closed circuit, mower won't start. Plug the connector back on the switch and it fires right up.

Growing up, my dad had a small engine repair shop. we bypassed the wiring on the mowers and had no problem. Weird.

 

[Duck]

Growing up, my dad had a small engine repair shop. we bypassed the wiring on the mowers and had no problem. Weird.

I've done it to a ton of mowers. It was just one that wouldn't cooperate.

Owner was a tiny little 85 lb woman, and the seat had heavy springs under it, and her yard was lumpy, so every little bounce made it momentarily cut the ignition.

I ended up removing the springs under the seat and annealing them with the torch so they'd be weaker and her little ass could compress them enough to keep the engine running when she hits bumps.

It solved the problem.

 

[Rigjockey]

Sad that a feature like this needs to even be a thing to prevent wheel holders from flat-spotting tires and brake fires.
The low air warning should be enough without adding another sensor.

 

[Duck]

It's probably got to be maintained too.

@Mike if you bypass that stupid thing, and then get into a fatality accident, the lawyers would say that you "disconnected safety equipment from the braking system".

 

[Mike]

It's probably got to be maintained too.

@Mike if you bypass that stupid thing, and then get into a fatality accident, the lawyers would say that you "disconnected safety equipment from the braking system".

Exactly. And it is just a redundant system

 

[Rigjockey]

Maybe we should bring back the Wig-wags for the wheel holders.

Here is your sign

 

[Hillbilly Canuck]

Maybe we should bring back the Wig-wags for the wheel holders.

Here is your sign

Wouldn't work. They already can't see signs for things like low bridges, weight limits, construction zones, and according to the Humboldt wheel holder even multiple stop signs seem...... nonexistent.