I'm replacing the D-2 governor. From the looks of it and the how tough it was to break the mounting bolts loose, I'm guessing it has been in there a long time. Anyhow, I was just plugging the unused ports when I noticed the existing D-2 has an open port. It's threaded and leads into the unit just like the others. Is this port normally left open? Thanks.
jor
Blow off?
Correct, blow off or vent, must be left open to cycle
Excellent. Thanks, guys.
jor
jor,
That is the exhaust port and should be left open. When transitioning to cut-in, air from the unloader port escapes and the unloader valves re-seat so the compressor starts compressing again. My unloader valves were stuck shut and the compressor was always building air.
Jerry
I am a strong believer that that open exhaust port located on the Governor is an easy way for dirt, water, and you name it to get into the unit. We recommend a brass elbow & barb fitting with a foot or so of rubber hose facing down. This will allow the governor to exhaust, and prevent wash water, and other debris from falling into it.
Here's a couple of excellent demo videos on the operation of the air governor and unloader. If the exhaust port on the governor is plugged the unloader valves will stay closed and the compressor keeps building air.
I had to replace the stuck closed unloader valves on mine. You can test them with a supply of air from a small portable compressor connected to the unloader port as shown in the video. If the unloader valves are stuck closed the big compressor will run all the time even though the governor still controls the cut-in and cut-out psi. The result is an overworked compressor that never gets a break!
Jerry
http://www.youtube.com/watch?v=9Vb32PL1PVU
http://www.youtube.com/watch?v=y6u_hFztHZo
Got the new D2 in. Replaced the steel fittings with brass and adopted Barry's exhaust hose scheme. Upped the air pressure to about 120psi.
I need to replace the air dryer but it might be more than I want to handle. It looks tough to remove and all the fittings have suffered many northern winters. I may have someone else do it. Never know though!
jor
John, Cindy & I changed our air dryer with a NAPA bought rebuilt in a campground on a picnic table. Price was good and it came with new filters. Removing air hose flare fittings were not a problem. Removing NPT right angle fittings were difficult but doable with a pipe wrench. Take photo before taking apart to help fitting angles. Brass 'econ' valve must be transferred and maybe cleaned out or replaced.
Good time to make and test emergency bypass fittings.
Remanufactured Haldex Air Dryer (http://www.foreforums.com/index.php?topic=13726.msg77099#msg77099)
Haldex Isolation Valve (http://beamalarm.com/Documents/haldex_isolation_valve.html)
Emergency Air Dryer Bypass (http://beamalarm.com/Documents/emergency_air_dryer_bypass.html)
Just a quick note about the hose fittings which are a JIC (37 degree flare) style:
It's important to not tighten them too much or else it can actually cause a leak by deforming the seal surface.
I know Cummins in recent years has converted the fuel system on some engines from JIC to O-Ring Face Seal because of this.
The O-Ring Face Seal is a flat surface with an o-ring in a groove on one side - it can't be damaged by over tightening - except by stripping threads - which is well beyond what even a garage gorilla would apply.
The link below is a simple and easy method to tighten JIC fittings. The size dash numbers are 1/16" of an inch. Most hoses measure about 1/4" over the dash size on the OD. You will also find the dash numbers at the end of the hose and fitting part numbers if the lettering is still legible on the hose or fitting.
How to Tighten JIC Fittings (http://www.new-line.com/information/how-to-tighten-jic-fittings)
John, interesting info indeed. Thanks
JohnH
"Upped the air pressure to about 120psi." Jor, is that the upper limit (where the air system purges)? Is that what your dash gauge shows?
I know that at least some D2 governors are adjustable, and I think mine is one of those. While driving, the air pressure goes up to just over 120 by the dash gauge, then slowly drops to about 110, then climbs back up to just over 120. This cycle takes several minutes. I know I have some air leaks, but haven't taken the time yet to track them down.
Yes. Mine was about 105. Lots of threads on this. One advantage of a higher number is you can air your tires with the coach air with less difficulty.
That's normal behavior.
I'm still chasing leaks. I found two yesterday in the entry step system but I could not locate any others. I lose all air overnight.
jor
That is pretty neat. I always second guess myself when tightening those things. Just never quite sure how tight. I'm printing this one out. Thanks.
jor
Jor- I had Issac at Old Town Motorcoach replace my air dryer. He struggled big time with some of the fittings with 2 pipe wrenches and a vise. If you know Issac and see how big and strong he is, I was glad I made the decision to have him replace it instead of me.
^.^d ^.^d
X2. I took ours apart in our driveway. It IS do-able, but may require some creative ways of applying sufficient leverage. Think BIG wrenches and long cheater pipes...loud 4-letter words directed at the fittings...several rest breaks in the shade to "cool off".
David, it is normal for air pressure to be lost while driving, from air bag movements that trigger ride height valve exhausting. And we all see the dance between about 120 psi and 90 psi over and over, more so on rear where there is more body movement. We also set ours to about 120 psi max, easy to change by removing top plastic cap on governor and rotating adjusting screw. Another advantage of raising is staying above HWH low pressure warning buzzer set point.
I see yours has the isolation valve as does ours. Is your air compressor a Holset? I remember reading somewhere that the Bendix and Wabco compressors don't require it.
Don
It's a Bendix AD-9, and that's the way it was rigged when we bought the coach. I ass-u-me that it is correct - seems to work fine. I replaced the isolation valve with a brand new one on the last rebuild.
...loud 4-letter words directed at the fittings...Chuck I thought I was the only one who cursed like Ralphy from "A Christmas Story" when working on difficult projects. And i suppose the priest wasn't throwing water on me to cool me off???