Chock your wheels and release the brakes. Do a walk around. If you hear air escaping and pinpoint it to a chamber, then you have a bad emergency chamber... in which case, you'll probably hear it escaping from the purge valve between the two axles, and you'll need to take a set of pliers or vice grips and pinch off the lines to each chamber to determine which brake chamber is bad.
After that, press the treadle valve (brake pedal)... I use a hood prop rod for this... you can buy them at any auto parts store, although I bought mine from Snap-On (they're also handy for when you have to adjust a clutch). Check again for air leaks... if it's coming from the service chamber in this instance, it's a problem with the service chamber, and you should be able to pinpoint the specific brake chamber by sound.
The hold off pressure for the spring brakes if 60 psi, and brake chambers are regulated at 90 psi.
brake light switch is bad
More than likely, there is air in the brake line or a leak in the line. Go to a mechanic and have the brakes "bled". He'll know what you are talking about. It's fairly inexpensive to do. Bad brakes, bad master cylinder, broken brake line, low brake fluid.
bad or out of adjustment brake switch on the brake pedal arm
# Bad brake light switch (on top of the brake pedal under the dash), or; # A shorted turn signal switch.
In general they leak hydraulic brake fluid when they go bad.
First, you need to determine if that's the problem. If you have a co-driver, or someone who can simply push on a brake pedal, get them to help you. Kneel down at the end of your trailer while they depress the brake (they can use the foot brake or the Johnson bar - it really doesn't matter), and listen for sounds of air escaping. If you hear that, get under the trailer and try to pinpoint whether or not it's coming from the brake chambers.Obviously, while you do this, you'll have your tractor air pulled out to engage the spring brakes on your tractor, and your emergency/trailer air pushed in so that air continues being delivered to the trailer.There could be a number of reasons for brake chamber malfunction, but the most common is simply a bad or worn out seal. Inside the brake chambers, an "O" shaped rubber gasket can be found. They do go bad over time.Your problem might be with your brake chambers, just as it might be a problem with air line crimping or other blockage, or with the brakes themselves (although brake problems don't often happen to all sets of brakes on a trailer at once, but discount no possibilities until you know for certain what it is).If this is a government-owned vehicle, they probably don't consider this an operator level task, and would have you either take it to your unit maintenance, or they would summon a professional third party entity to conduct the repairs.
Brake light switch went bad.
Answer: Brake calipers (front or rear) normally "go bad" because the dust seal was not replaced, thus allow dirt to get onto the piston as the brake linings wear down. When you go replace the linings and DON"T clean the piston, it allows the dirt to damage the caliper bore. NORMALLY, brake calipers leak and can be overhauled with a few sealing rings, and a good bleeding of the brake system.
It is on the steering column, but those rarely go bad. In fact, I have never had to replace one. Almost always it is because you have no brake lights. Possibly a bad brake light switch.
Ernie Chambers goes by Senator Ernie Chambers.
Bad brake booster.