Eng air compressor cycling

[William Mathews]

While going doen the road, the eng. comp. cycles from 1 to 5 minutes. When stopped, eng running, the comp. does not cycle. When stopped, brake on, I get out to listen for air leak, but hear none. When stopped, eng off, brake on, I listen for air and hear none. When park, air press. will bleed down to 85 psi in 3 days, down to 60 psi in 5 days. In 2 weeks the press will be almost zero. I think going down the road, the ride height valves are adding and releasing press as you bounce along. But cycling that much seems excessive to me. Any thoughts/advice would be welcome.
Bill M
o3 Cont.

[Joel Weiss]

My MH behaves exactly the same and I've been told there is nothing wrong with it.  The loss of pressure over multiple days is not something these systems are rated for; air brake performance tests are concerned with pressure loss in "minutes" not "hours."

[Edward Buker]

My coach is a 2002 Marquis and it uses a lot of air going down the road similar to what yours does. I have even seen it cycle in a bit less than a minute at times on a rough non paved section of a road being repaired. You may want to block the wheels and turn the parking brake off which will flow air to the rear chambers to hold them off and see that there are no leaks there by watching the guage with engine off.  My leak down rates are similar to yours with the coach standing still and the engine off. I was told that the valving on these coaches is very dynamic with higher flow rates and faster response times then we were used to in older coaches and these higher flow leveling valves were used to enhance the ride performance and stability. I have learned to live with that compressor cycling and keep one eye on the guage a bit. Might be good if others chimed in with their compressor cycling experince also to see the range of normal. Five minutes would be longer then I get on the long end I think...

Later Ed

[Gerald Farris]

Bill,
Your air system is performing within specifications with the pressure reading that you listed. If you have an air leveling system, your air system will not go to zero in both tanks if it is on, because the electric leveling system compressor will run enough to keep the tank that is supplying the leveling system supplied.

Gerald

[William Mathews]

Thanks for those inputs as I was a little concerned about how often the eng. comp. cycles. When I park here at the house, I don't use air bag leveling as the parking spot is pretty level. Thanks for that tip about blocking the wheels and leaving the brake off, I'll do that. I only mentioned the brake in the original post so people wouldn't think I was getting out with the eng. running and no blocks or brake.
Bill M
03 Contessa

[Edward Buker]

Gerald while we are on the subject of the coach compressed air system, I have noticed something on mine that I am not sure is normal for others. When I dump air for leveling, I will hold the air dump button until the green needle drops to near zero manually before I start the leveling system air dump and begin the hydraulic "ride" of my leveling system. The red needle seems to drop with the green to a point, maybe 50lbs (not sure), and then stay. That is normal (I think) as a safety reserve pressure point. What happens next is over a period of the next few days some amount of air will slowly bleed from the red into the tank associated with the green needle. That raises the coach off the hydraulic level system axle pads somewhat which alters the coach level some and I have to manually dump the air several times more to settle back down on the hydraulic axle pads before all of this air is fully depleted. It is not such a big deal but I am thinking some check valve has a slow leak within the system maybe. I was wondering if you had some idea regarding this issue or if some other owner with this SMC leveling system has witnessed the same thing. It may be normal that the valving/check valve has this leak rate, it is very slow.

 I think you folks with air leveling could have the same situation but would never notice it due to the fact that your air leveling would maintain proper pressure itself while at rest or the tank or line (green needle) that I need at 0PSI would have pressure in it and therefor the air would not pass.

Happy 4th to all and a thanks to all that served....Later Ed

[Gerald Farris]

Ed,
I think that the conditions that you stated are fairly normal, however I am certain, since I almost always air level my coach. However on the few times that I do level hydraulically, I have never noticed the air suspension reinflating after leveling. Although since my coach has HWH systems, there may be no correlation between the two coaches.

Gerald