Help! How Is Anyone Supposed To 'accurately" Read An Air Pressure Gauge Like This One?

Topic 23526 | Page 1

Page 1 of 4 Next Page Go To Page:
Soulin H.'s Comment
member avatar

I will be taking my DMV Driving Test in a few days. My question/s: The main question is in the topic: "How is anyone supposed to 'accurately" read an Air Pressure gauge like this one?"

Why would anyone make a gauge with 30 psi increments instead of the standard 10 psi?

It seems to me so absurd! 1/2 way between 90 and 120 is 115 for example, but a driver is supposed to be able to 'accurately' read 3 psi for the Static Leakage Test after, of course, 'accurately' reading the air pressure after the readings on the gauges have 'stabilized'.

On this gauge, where exactly is 100 psi, or 85 psi?... ...what about 140 psi?... ...or 20, and 45 psi?... ...etc.

0285216001538269056.jpg

Dm:

Dispatcher, Fleet Manager, Driver Manager

The primary person a driver communicates with at his/her company. A dispatcher can play many roles, depending on the company's structure. Dispatchers may assign freight, file requests for home time, relay messages between the driver and management, inform customer service of any delays, change appointment times, and report information to the load planners.

DMV:

Department of Motor Vehicles, Bureau of Motor Vehicles

The state agency that handles everything related to your driver's licences, including testing, issuance, transfers, and revocation.

Old School's Comment
member avatar

Soulin, you're getting ahead of yourself. That is not the gauge that shows a loss of air pressure during the "Air Brake Test."

That guage indicates how much air pressure you're putting into the brake system by applying pressure with your foot to the brake pedal. The pressure on that guage will continuously change with any change you make in the pressure you are applying to the pedal.

You're overthinking this because you aren't even looking at the proper air pressure guage.

Slow down. They will show you how to do this in school. smile.gif

Old School's Comment
member avatar

Oooops, maybe you are already in school. You need to ask your instructor to show you which guages to watch for the test. That is not the correct one. You should have two other air pressure guages that show the stored air pressure in the air tanks. That's where you will determine if the pressure is leaking down.

andhe78's Comment
member avatar

You are way over thinking this. The gauge is set up for the numbers you need. 90, compressor comes on. 120, compressor cuts off. 60, warning buzzer comes on. 30, valves should pop.

As for the 3 psi, you aren’t actually measuring it, if the needle is holding steady after it’s stabilized, you’re good. If it’s dropping and you can notice it in that minute after it stabilized, you have a leak.

Old School's Comment
member avatar

Actually, I'm mistaken. That is the proper guage. Go with Andhe78's response. He is dead on!

Old School's Comment
member avatar

I'll go to bed now, and try to come back in here when I can make some sense! smile.gif

PlanB's Comment
member avatar

As others have said, don't over think it.

This is what mine looks like.

0112839001538273445.jpg

Just as vague as the one you posted.

For the static leakage test your basically just watching to make sure the needle doesn't continue to drop as your holding the brake.

Soulin H.'s Comment
member avatar

RE:

You are way over thinking this. The gauge is set up for the numbers you need. 90, compressor comes on. 120, compressor cuts off. 60, warning buzzer comes on. 30, valves should pop.

Actually not. CA CDL Manual says:

"*Air Compressor Governor Cut-In Pressure Test To perform this test, the air pressure for the vehicle cannot be rising when the engine is running. With the air pressure at maximum pressure (cut-out), begin slowly pumping the brake pedal to reduce the air tank pressure. Watch the air pressure gauge between pumps to identify when the compressor cuts-in (needle starts to rise). This must occur no lower than 85 psi for a bus, and no lower than 100 psi for trucks."

Just as vague as the one you posted.

Sure is albeit different and a 2-in-one single gauge. The one in the photo I took is just the primary, the secondary is exactly same except it has the number 2 instead of the number 1 on it.

For the static leakage test your basically just watching to make sure the needle doesn't continue to drop as your holding the brake.

It is a definite fail at the DMV on the Air Brake Test to press the "Service Brake" and reefer to it as the "Static Leakage Test".

Pressing the "Service Brake" and holding it down steady for 1 minute is the "Applied Leakage Test" on the "Service Brakes".

California DMV CDL Handbook says:

"Test Air Leakage Rate There are 2 tests as follows: Static Leakage Test With a basically fully-charged air system (within the effective operating range for the compressor), turn off the engine, release all brakes, and let the system settle (air gauge needle stops moving). Time for one minute. The air pressure should not drop more than: • 2 psi for single vehicles. • 3 psi for a combination of 2 vehicles. • 5 psi for a combination of 3 or more vehicles. Important: The maximum air loss rate for a combination of 2 or more vehicles is 2 psi if the towed vehicles are not equipped with air brakes. An air loss greater than those listed above, indicate a problem in the braking system and repairs are needed before operating the vehicle.

*Applied Leakage Test

To perform this test, the vehicle’s air pressure should be built up to maximum pressure (cut-out). With the air pressure built up, shut off the engine, chock the wheels if necessary, release the parking brake (all vehicles) and the tractor protection valve (combination vehicle), and firmly apply the foot brake. Then hold the foot brake for 1 minute after stabilization of the air gauge. Check the air gauge to see that the air pressure drops no more than 3 psi in 1 minute (single vehicle) or 4 psi in 1 minute (combination vehicle) and listen for air leaks. You must identify how much air the system lost and verbalize the maximum air loss rate allowed for your vehicle. • 3 psi for single vehicles. • 4 psi for a combination of 2 vehicles. • 6 psi for a combination of 3 or more vehicles. Important: The maximum air loss rate for a combination of 2 or more vehicles is 3 psi if the towed vehicles are not equipped with air brakes. An air loss greater than those listed above, indicates a problem in the braking system and repairs are needed before operating the vehicle. Note: For testing purposes, you must be able to demonstrate this test and verbalize the allowable air loss for your vehicle. If the air loss is too much, check for air leaks and fix any that are identified. For testing purposes, identify if the air loss rate is too much.

Just sayin.

Anyway I was hoping for someone who has experience with the specific gauge scale as what I have to test with to chime-in.

Thanks to all for trying... ... sorry.gif But no cigar

CDL:

Commercial Driver's License (CDL)

A CDL is required to drive any of the following vehicles:

  • Any combination of vehicles with a gross combined weight rating (GCWR) of 26,001 or more pounds, providing the gross vehicle weight rating (GVWR) of the vehicle being towed is in excess of 10,000 pounds.
  • Any single vehicle with a GVWR of 26,001 or more pounds, or any such vehicle towing another not in excess of 10,000 pounds.
  • Any vehicle, regardless of size, designed to transport 16 or more persons, including the driver.
  • Any vehicle required by federal regulations to be placarded while transporting hazardous materials.

Combination Vehicle:

A vehicle with two separate parts - the power unit (tractor) and the trailer. Tractor-trailers are considered combination vehicles.

Dm:

Dispatcher, Fleet Manager, Driver Manager

The primary person a driver communicates with at his/her company. A dispatcher can play many roles, depending on the company's structure. Dispatchers may assign freight, file requests for home time, relay messages between the driver and management, inform customer service of any delays, change appointment times, and report information to the load planners.

DMV:

Department of Motor Vehicles, Bureau of Motor Vehicles

The state agency that handles everything related to your driver's licences, including testing, issuance, transfers, and revocation.

Reefer:

A refrigerated trailer.

HOS:

Hours Of Service

HOS refers to the logbook hours of service regulations.
Big Scott (CFI Driver/Tra's Comment
member avatar

First off that gage is a precision instrument. The first line between 0 and 30 is the point your valves should pop. As far as measuring air loss on the test what andhe78 said is correct. Good luck. Also ask your instructors to explain it to you.

Big Scott (CFI Driver/Tra's Comment
member avatar

For the test your school will teach you exactly what to say. You must memorize it. You must understand it. Your instructors can explain that gage better. But the unmarked lines are the ones to look at. Some trucks have two gages some have one with two needles.

Page 1 of 4 Next Page Go To Page:

New Reply:

New! Check out our help videos for a better understanding of our forum features

Bold
Italic
Underline
Quote
Photo
Link
Smiley
Links On TruckingTruth


example: TruckingTruth Homepage



example: https://www.truckingtruth.com
Submit
Cancel
Upload New Photo
Please enter a caption of one sentence or less:

Click on any of the buttons below to insert a link to that section of TruckingTruth:

Getting Started In Trucking High Road Training Program Company-Sponsored Training Programs Apply For Company-Sponsored Training Truck Driver's Career Guide Choosing A School Choosing A Company Truck Driving Schools Truck Driving Jobs Apply For Truck Driving Jobs DOT Physical Drug Testing Items To Pack Pre-Hire Letters CDL Practice Tests Trucking Company Reviews Brett's Book Leasing A Truck Pre-Trip Inspection Learn The Logbook Rules Sleep Apnea
Done
Done

0 characters so far - 5,500 maximum allowed.
Submit Preview

Preview:

Submit
Cancel

Join Us!

We have an awesome set of tools that will help you understand the trucking industry and prepare for a great start to your trucking career. Not only that, but everything we offer here at TruckingTruth is 100% free - no strings attached! Sign up now and get instant access to our member's section:
High Road Training Program Logo
  • The High Road Training Program
  • The High Road Article Series
  • The Friendliest Trucker's Forum Ever!
  • Email Updates When New Articles Are Posted

Apply For Paid CDL Training Through TruckingTruth

Did you know you can fill out one quick form here on TruckingTruth and apply to several companies at once for paid CDL training? Seriously! The application only takes one minute. You will speak with recruiters today. There is no obligation whatsoever. Learn more and apply here:

Apply For Paid CDL Training

About Us

TruckingTruth was founded by Brett Aquila (that's me!), a 15 year truck driving veteran, in January 2007. After 15 years on the road I wanted to help people understand the trucking industry and everything that came with the career and lifestyle of an over the road trucker. We'll help you make the right choices and prepare for a great start to your trucking career.

Read More

Becoming A Truck Driver

Becoming A Truck Driver is a dream we've all pondered at some point in our lives. We've all wondered if the adventure and challenges of life on the open road would suit us better than the ordinary day to day lives we've always known. At TruckingTruth we'll help you decide if trucking is right for you and help you get your career off to a great start.

Learn More