[qcj]

Just got back from a trip yesterday and on the way back, I noticed that the supply air tank gauge would drop to 90 lbs and immediately go to 115 lbs. then drop back to 90 lbs. in a period of about a minute. I ask my wife, which can hear better than I, to walk around the coach when we got home and coach in storage and engine off to see if she could hear any air leaks. As fast as it was going down it should be heard. She or I could not hear anything, and the gauge did not move. My 110 volt compressor cuts on about every hour and a half. How long it has been doing this I don't know, because I usually just glance down at the gauges then back to road. The brake gauge is working as it should. Whats going on here?

[Fulltiming]

How long does it take to drop from 115 to 90 and how long does it take to go back to 115. Incidentally, both of these pressures are lower than my system which cycles in at 105 psi and the compressor cuts off again at 125 psi. As you are traveling down the road, the air suspension is in travel mode and the bumps and undulations in the road result in air being vented from the suspension system. Fast acting ride height valves will bleed down the air system much faster than slow acting ride height valves. My coach has the blue plastic replacement ride height valves (fast acting) and they seem to cause the air system to discharge air and thus kick in the engine driven air compressor somewhat faster than the original black ride height valves did prior to the time that they developed cracks and started leaking huge amounts of air.

When the coach is not in motion, the affect of the valves dumping when a wheel drops is eliminated so you would likely not hear a leak. If the valves are cracked, you will hear a BIG leak but you certainly have part of your air system tight if your 110 volt compressor only kicks in every hour and a half. When my ride height valve bodies cracked, it depended on the level of that valve as to whether it leaked like crazy or didn't leak at all when the coach was stationary.

Depending on the frequency of the engine driven compressor kicking in, your situation could be normal. If the frequency of the engine driven compressor cycling has changed dramatically then you may have a valve issue.

[rheavn]

By your description, you only have a leak when the engine is running? What does the supply guage do once you shut off the engine? Does it go to zero in just a few minutes? If it was leaking when the engine was off the 110V compressor would be running every minute or so. A compressor that runs every 1 1/2 hours indicates only very small air leaks in your auxiliary air system.

I agree with Michael. If air is not leaking with the engine off, I would be looking closely at the six packs(front and rear) and the ride height control valves with the engine running.

[Chester Stone]

Chappell, with your compressor starting up after an hour and a half, you likely have a leak, but not enough to change the gauge every minute. First, I would check to be sure there is no water in the air tank. Secondly, you can purchase a cheap air gauge to install in the air tank bay at the "T" just above the cut off switch. At the moment I cannot recall the brand, but you can purchase from Harbor Freight a tool that can hear an air leak that the human ear cannot. This tool helped me locate many air leaks and my compressor seldom runs now.

[qcj]

Michael, to answer you question. It will cycle from 90 to 115 in about one minute, very quickly. You can see the needle drop and see the needle come back up. When engine is not running the 110 comp. will cycle from about 75 cut on to about 95 cut off. When engine running the two brake needles stay at about 110 lbs unless I apply the brakes then the white needle will drop but quickly come back up.

Steve the supply gauge will stay at the pressure it was when the engine is cut off. Yesterday it was at 110 lbs and stayed there. Did not move while I was unloading the coach. Probably 10 minutes. Of course it will slowly go down until it is about 75 then the 110 cuts in in an hour or so. There should not be any or a very little water in the rear tank. I pulled the lanyard on the rear tank, the only tank that has a lanyard, before I left for home, a little over 200 miles. Not much water came out. Drained the other front tanks and the small tank in the rear wheel well before I left.
Thinking back, one thing I do remember is yesterday when we pull over for lunch I did not have the 110 comp. on because I was on inverter and the supple gauge was on zero when I cranked the engine after being there for about 30 minutes. I thought that was strange at the time. I was in ride height. Now when I put the coach up yesterday I raised the coach up as high as it would go and blocked it. Maybe if I left it in ride height things would have been different. Maybe it is the six pack. I'm going to change the oil before my next trip and I will run the engine to warm up the oil and after I've changed the oil I will remove the blocks crank the engine and bring it down to ride height and do some checking at the six packs, etc. I doubt one would be able to hear a leak with the engine ruining but I will have my wife give it a try. Any other suggestion will be appreciated.

[qcj]

I must say that yesterday when I stopped for lunch it was 12 degrees out and I just thought that was the reason for the drop in air.

[Richard]

I suspect, as others, that you have a ride height valve issue. It is entirely possible that one could have iced up on you. Before I went any further, I would wait till the temp is above freezing, and go for a drive and see if it repeats. Ice causes all kinds of weirdness in the pneumatic system.

[rheavn]

This tool has been very helpful for me to find air leaks. I could hear a leak like you describe with this tool even with the engine running. I will have the tool at the rally in June that any one is welcome to use.

http://www.amazon.com/Inficon-711-202-G1...on+whisper

Disclaimer: Others have used this tool with less successful results. Also there are many other tool makers of similar tools.

[qcj]

Richard, that is a good idea. It was very cold, but dry and I had only one thing on my mind and that was to get home before anything fell out of the sky. The sun was not out. I did have trouble opening a couple of my bay doors that were iced up. I was at this park (Ink Lake State Park) W. of Austin, TX for about a week and for most of the time the weather was great. We planned to leave Sunday but very cold with frozen rain so decided to wait until yesterday.
I just got back from the MH, and I cut the 110 comp. off and watch the air pressure and it lost 15 pounds in a little over an hour and it was 44 degrees inside the storage. This is about what it has been doing. When the weather is warmer it loses less.
Steve I bought one of these things and I have trouble hearing anything with it even with muffs. I know you do well with yours and that is great. When in Ark. you need to show me what I am doing wrong.

[smagown]

My supply gauge was erratic and wouldn't pump up and I knew I didn't have a leak big enough for the supply side not to release the emergency brake at around 65 lbs. The only leaks I have had this big were a cracked height control valve and the hose coming off the Aux compressor broke. I replaced the big air dryer filter behind the driver's side tag and drained my tanks and the problem was solved. I then installed the air dryer with the electric solenoid on the Aux compressor. Now when the compressor stops, the valve opens and drains the water out of the bowl. In our humid climate the bowl could fill in a day. So far so good.