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Author Topic: airpressure on C9 400HP 2007  (Read 942 times)

Uwe Schmalenbach

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airpressure on C9 400HP 2007
« on: April 15, 2017, 10:29:17 PM »
I have a 2007 Contessa 40' with a C9 400HP . Yesterday after starting the engine I got a "Low Air" sign and even after 20 min of engine running no air pressure. After tapping on the governor I finally got a slow buildup of air. On the recommendation of a mechanic I replaced the WABCO air dessicant cartridge of the air dryer and had a slow buildup of air pressure to about 135psi. During driving the coach for about 100 miles I noticed that the air pressure normally was at about 115-120psi but during long slow city downhill driving the pressure dropped to about 75psi and did not buildup during downhill driving but did build up when accelerating again on flat ground.

The long time of low air pressure during downhill driving concerns me because according to the operating manual the pressure should be between 115 and 135psi. The question is "what should I be doing to keep the air pressure above 75psi ?"

Should I replace the governor or what else?

Uwe Schmalenbach
2007 Contessa 40'
CAT C9 400 hp

Edward Buker

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Re: airpressure on C9 400HP 2007
« Reply #1 on: April 15, 2017, 11:29:35 PM »
Uwe,

This seems more like a volume of supplied air problem rather than the control of the compressor online or offline pressure that is controlled by the governor. If under highway travel the compressor cuts in at 115 lbs or so and off at 125lbs then the governor is working. You need to check the compressor output volume and if you have any air leaks in the system that is consuming air when it should not be. Leaky air line valve or fitting, open pressure relief valve etc.

Later Ed

Gerald Farris

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Re: airpressure on C9 400HP 2007
« Reply #2 on: April 16, 2017, 01:06:26 AM »
Uwe,
I can agree with Ed in that you should check thoroughly for any air leaks, but you description of no air pressure after 20 minutes of idling until you tapped on the governor, and then the air pressure came up, sounds like a bad compressor governor. Because a compressor governor can be problematic to locate when you are one the road, and they are only about $70 or so, I would change it.

I know how problematic it can be locating a governor because last fall, the governor failed on my coach one morning in the middle of Nevada and the closest replacement was a 8 hour round trip in the tow car and over an hour of work in 30 degree weather before I could move the coach to head for warm Arizona.

Gerald         
2002 Solitaire (2017 -  )
2000 Marquis, C12 (2004 - 2017)
1993 Patriot  (2000-2004)

Uwe Schmalenbach

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Re: airpressure on C9 400HP 2007
« Reply #3 on: April 19, 2017, 11:22:13 PM »
Thanks for the response. I replaced the governor and the dessicant cartridge but the real problem was that the turbo discharge valve, which is separate from the discharge valve on the WABCO air dryer, was leaking and also had to be replaced. In addition the governor had to be readjusted because it started with 150 psi pressure and opened the safety pressure release valve next to the generator. After 5 hours everything was working fine thanks to a good team at the FJM truck repair facility in San Jose Ca.
2007 Contessa 40'
CAT C9 400 hp

Joe Rhea

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Re: airpressure on C9 400HP 2007
« Reply #4 on: April 20, 2017, 12:24:34 AM »
UWE:
Where is the turbo discharge valve located I don't see the relation ship
2005 Monterey Laguna IV 40'
C-9 Cat 400 HP
San Leon, Tx.

Uwe Schmalenbach

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Re: airpressure on C9 400HP 2007
« Reply #5 on: April 21, 2017, 12:02:27 AM »
On the WABCO airdryer  the turbo discharge valve it located under the dryer close to the main discharge valve, on the Contessa in front of it
2007 Contessa 40'
CAT C9 400 hp

Joe Rhea

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Re: airpressure on C9 400HP 2007
« Reply #6 on: April 21, 2017, 12:50:25 AM »
Thanks
I found it on the cutaway of the drier
2005 Monterey Laguna IV 40'
C-9 Cat 400 HP
San Leon, Tx.

Joe Rhea

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Re: airpressure on C9 400HP 2007
« Reply #7 on: April 25, 2017, 04:11:06 PM »
I'm hoping someone has the Bendix part number for the air governor. I didn't see any numbers on the existing governor but I haven't pulled it off either. Just wanting to order one before I actually have a problem.
Thanks 
Joe Rhea
2005 Monterey Laguna IV 40'
C-9 Cat 400 HP
San Leon, Tx.

Lee Welbanks

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Re: airpressure on C9 400HP 2007
« Reply #8 on: April 25, 2017, 10:20:29 PM »
Joe, the Bendix part # 275491 it is whats call a D2.
Lee, Judy  & Pepper
06 Beaver Patriot Thunder
Wilmington IV 40
525 Cat, 4K Allison
2013 Honda CRV

Joe Rhea

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Re: airpressure on C9 400HP 2007
« Reply #9 on: April 25, 2017, 10:36:34 PM »
Thanks Lee
 I really appreciate it.
Joe
2005 Monterey Laguna IV 40'
C-9 Cat 400 HP
San Leon, Tx.

Lee Welbanks

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Re: airpressure on C9 400HP 2007
« Reply #10 on: April 26, 2017, 12:28:45 AM »
Joe, here's a link to a video of how one works and which line goes where.
https://www.youtube.com/watch?v=FHGcXvDmZ5E
Lee, Judy  & Pepper
06 Beaver Patriot Thunder
Wilmington IV 40
525 Cat, 4K Allison
2013 Honda CRV