-
Purge Valve on AD-2 Air Dryer
Last week service was completed on the subject dryer that included removing and throughly cleaning the internals, installing a new dessicant kit, verifying voltage at the electrical terminal, measuring resistance across the thermostat, heater, and heater element. All were within the limits specified by Bendix. The only part not checked was the purge valve because the large nut on the end cap would not budged. How does one verify that a purge valve is working properly?
In testing and checking for leaks, the following was noted:
- In bringing all tanks back up to pressure, the “piss off”seemed muffled.
- There were no leaks at the dryer.
- The primary dash pressure gauge reading increased from the normal of around 125 psi to just over 130 psi. The secondary gauge reading remained just over 120 psi.
- The brakes past the DOT brake test although the recovery time was a bit slow – around 3 minutes.
- Although no leaks were observed in the work performed, a leak was noted in the rear left 5-way 3- position Norgren valve. Air was being expelled from a tiny rectangular notch where the 1/4 ” lines connect to the number 12 position. Tightening the four mounting screws did not correct the problem.
- Exercising the level low switches on the dash did not appear to move the bus beyond driving height. Nothing was checked in the steer compartment due to time constraints.
- The pressure gauge readings on the dash remained constant after 30 minutes or more later.
Your thoughts on these results would be appreciated.
While under the bus, brakes were adjusted. Many thanks to Jon for his excellent article on adjusting brakes.
Best Regards to All,
-
2 Replies
-
Tom,
My impression of your dryer purge valve operation was that it is functioning as it should. The pressure on your coach I believe is independent of the dryer and is regulated at the compressor.
As to your question regarding the leaking Norgren, the end caps are unlikely to ever have pressure behind them unless air is leaking past the spool. Tightening the end cap will not solve the problem which is probably going to be cured with new spools or O rings for the existing spools. For what it is worth the 12 air port when pressurized maintains an open path between ports #1 and #2 by shifting the internal spool. That might be on a trivia quiz.
-
Jon,
Thanks for your help and response. I’ve come along way in understanding the pneumatics on my coach thanks to Hector, Tom and you but I probably couldn’t pass your quiz. I tend to freeze up when taking a quiz – its the age thing you know. Us old farts are slow on recall!
Log in to reply.