Ok, for the dryer purge valve, another possibility as it is triggered by air sent from the governor when it unloads the compressor. If the governor is leaking air down that line it could be forcing that purge valve to leak. You can disconnect that 1/4” airline from the bottom of the dryer and see if the purge valve stops leaking, and if any air is leaking out of it. Just be sure to secure it to something as it will go to 125PSI when the dryer unloads and will whip the crap out of things if not secured…
For CTIS it sounds like it didn’t drain cleanly whan the control valve opened, or a wheel valve didn't close immediately.
The problem with CTIS is it is hard to troubleshoot and look for leaks using the controller. It is way easier to manually pressurize the system to look for leaks and to trouble shoot other performance issues with the engine not running. you can do this 2 ways:
1. Under the passenger dash disconnect the output line from the PCU down to the wheels. Connect an air fitting to this line and feed it from a regulator set to ~60PSI. This will charge and supply the whole system and you can look for leaks. This is the best way to do an initial leak check.
2. fill the tanks and shutdown. With the controller disconnected, put a jumper in the cannon plug from H to R. With the main switch on, this will close the control solenoid and allow the system to hold pressure. Next momentarily jumper from H to B. This will open the supply valve and feed wet tank air into the system. It only takes a second of air to open the wheel valves and with the control valve closed the system should stabilize and set at tire pressure. You can jumper H to C, to open the deflate solenoid and test the dump valves. When done dumping remove H-C and again briefly jump H to B to give a shot of air to stop the dump, or remove H to R jumper or turn off the main sw to open control and vent the system. This is the best way to test PCU and wheel valve operation, but not a good way to look for leaks, as once pressurized, a leak can cause it to start dumping if the truck side leaks below tire pressure…
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