Spring Pop-Out Test

I am posting this here because I feel this will help new CDL students and the experienced drivers can have a crack at it as well!

Recently, we (company) have been debating about the Spring Pop-Out Test / making sure the Tractor Protection Valve (Red Knob) "pops-out" or "triggers" between 20-45 PSI. Here is the question. I have the answer straight from the CVSA so my source is pretty solid. This was a tough one. I'll post the answer given to me by the Commercial Vehicle Safety Alliance after we get a debate going! ha...

QUESTION:

Does the YELLOW KNOB have to pop-out between 20-45 PSI?

 

Hmmm...I guess my question wasn't that big of a topic. Well, for newbees coming on here, I wanted to have something online that is searchable for this question.

To answer the question, when checking for the trigger of the tractor protection valve (Red Knob), the Parking Brake Valve (Yellow Knob) does NOT have to pop-out within the 20-45 PSI range. There is no FMCSARs or Federal Motor Vehicle Safety Standards which says so; therefore, if the DMV is testing you on this (Yellow Knob) and your truck's yellow knob doesn't pop-out within the range of 20-45 PSI, it's okay! But I bet the examiners don't know that...HELL most of those examiners don't have their Class "A" license and have never driven a truck cross-country before....funny how that works, right!

Do note, the Red Knob should trigger within 20-45 PSI. If it doesn't, then the truck fails.

 

VERY GOOD! THANKS Ridgeline!