Guages

Both are for both. Top is primary air & bottom is secondary air.

 

Yeah, you have two separate gauges for primary and secondary Air. The gauge that has the “Twin needle” setup is your two gauges in one. Either setup is fine. If you do have a gauge that measures trailer brake pressure it will sit at zero and build pressure as you apply trolly pressure. No guarantee that it comes factory. Some have, some don’t.

 

Both are for truck and trailer
Not separated

 

Neither gauge is for the trailer. One gauge is the truck's primary reservoir pressure and the other is the truck's secondary reservoir.

The only gauge you might have for trailer air would be one for trailer brake application pressure and that's not a required gauge so not every truck has it.

 

What @Largecar359 is saying is you have 2 gauges, Primary Tank (1) and Secondary Tank (2). On some trucks there is one gauge with 2 needles of different colors to differentiate the tanks, using the same pivot point. On a setup like that then the one in the foreground would be your primary and the one in the background would be your secondary. Here is a picture from Google to wit;

 

Sorry op, this is why our cdl program is such a joke, no fault of yours.

here are two publications for you to read, both are from Canada which I guess is required reading seeing Canadian drivers are always in a hurry lol..


https://www2.gnb.ca/content/dam/gnb/Departments/ps-sp/pdf/Publications/ab_manual-e.pdf

https://www.mpi.mb.ca/Documents/AirBrakeManualNEW.pdf