Originally Posted by RyRoRyan
So on yours, you talked about adding in a separate tank and what not to prevent pressure loss on the parking brakes. I am not sure on yours, but on mine, I have both a "P" guage/tank and a "S" guage/tank. I am assuming that "P" means primary and runs the brakes. "S" means secondary and it appears to run the rear air bags since that tank empties out when I level the coach. Does your coach have the rear air bags / second tank? I am under the impression that I should be able to tie an air horn into the secondary tank system without the risk of impacting my brakes....thoughts?
My 2014 has the rear Freightliner "AirLiner" air spring suspension, but since I do not have air brakes I only have one air "system" and no dashboard air gauge(s). My rig has hydraulically-boosted 4-wheel hydraulic disc brakes versus the newer units with air-actuated drum brakes.
On the older units like mine we do have a separate air-actuated driveshaft parking brake. If I lose all air it would come on as a safety measure, hence my addition of the pressure protection valve so I don't exhaust the air supply accidentally.
To your point, I do not know how Freightliner designed the air system, so I can't say whether tapping into the secondary side could compromise the air system. Your service brakes probably are are on the primary side, but your rear spring (parking) brakes might be on the secondary, as well as the rear suspension. I just do not know. If the rear spring brakes are on the secondary side, dropping pressure too low in that side might cause the parking brake to pop on unexpectedly. Bad news if you are rolling!