Low Air Suspension Issue

[OldForester]

We have an issue that's been going on with our coach for a couple years, and was worse this year on our annual Palm Springs 3 1/2 month journey. That issue is slowness in building up air pressure for the suspension when the coach is in colder temperatures.

When the outside air temperature is below approximately 50, and we have parked at least overnight and dumped the air, the coach when started will take longer to build up the air pressure until the warning light for "low air suspension" goes out and the spitter valve releases. Then if we start to move the coach we will get the "low air suspension" light come back on and the warning buzzer sound. Additionally, if we engage and release the parking brake, the button feels like it has low air pressure behind it.

If we wait a minute or two and drive the coach, all the low air issues will go away, unless it is near freezing. If it's that cold, we may have to move and stop the coach 5 or 6 times in a few hundred yards to get completely get rid of the buzzer, warning light, and soft feel to the parking brake.

Once we get past this stop and start routine, it's fine and we drive for the rest of the day with no issues. It happened on the way down to Palm Springs from Tacoma in December, and it happened on the way back last week, once we got inside the Oregon border and the temps went down to about 45 at night.

In various conversations over the last few months the most common suggestions was water in the air lines, which should go away with a lot of driving. We have driven it a lot since, and we still have the problem when the outside temperature gets below 50 degrees or so. Above that, there appear to be no problems.

A year ago we had the emergency brake switch checked for air leakage due to the "feel" issue, and the lines leading to it had some leakage. That problem was fixed, but the problem has persisted. Currently there doesn't feel like there's any air leakage around the brake switch.

Has anybody had this problem and fixed it? I've thought about an air pressure gauge but I get the same result by putting the parking brake on or off -- the "feel" tells me a lot about air pressure. Plus the gauge wouldn't tell me where the problem is.

Thoughts?

[EngineerMike]

If you have never replaced or rebuilt your air dryer, it may be time. IIRC it has desiccant in in to dry air before the unit heats up. After it has heat, the heat should dehydrate the desiccant. However, the stuff doesn't last an infinite number of cycles and the dryer needs to be serviced. I might have read somewhere you can blow the wet desiccant into the lines if you let it go too far, or maybe its too late at night and that's all just cobwebs fuzzing up my recollection. But I'm pretty sure you need to service the dryer every 3-5 years depending on run time & ambient conditions of service.

Although we don't use the air dryer for brakes, just suspension and filling tires, I goog'd "air dryer brakes" and got this link among other stuff. Searching iRV2 from the Forums root page will bring up several threads on dryer service that make interesting reading.

[Old Scout]

You didnt mention how often you use the moisture drain in the air filter/oil chk compartment. I probably dont use the drain enough but in addition to the air dryer, blowing the moisture out of the system via the air drain on a regular basis has to be a good thing--especially, if you are in a humid/cold climate.

[Basil Shannon]

Quote:

Originally Posted by OldForester When the outside air temperature is below approximately 50, and we have parked at least overnight and dumped the air, the coach when started will take longer to build up the air pressure until the warning light for "low air suspension" goes out and the spitter valve releases. Then if we start to move the coach we will get the "low air suspension" light come back on and the warning buzzer sound. Additionally, if we engage and release the parking brake, the button feels like it has low air pressure behind it. If we wait a minute or two and drive the coach, all the low air issues will go away, Thoughts?

We have seen this same issue a couple times in Palm Springs no less. I reset the brake, let the engine run for a few minutes and the problem goes away.

I have often wondered if there was some kind of maintenance required for the air dryer, a Haldex PURest in my coach. I found a Freightliner document that says you should replace the cartridge every 36 months or more often in humid climates.
Air Dryer Maintenance
WRV never covered it in our owner's manuals.

Anybody out there doing periodic maintenance on the air dryer?

[John&Nancy]

Old,
I had exactly the same problem recently which turned out to be the little sensor circuit board that is located behind the dash to the right of the steering column. If I remember correctly it is behind the lower of the two oval plates that are attached with two screws. I think it cost around $50 to replace.
John

[Algoma]

In my case the problem turned out to be a bad air compressor. Before you tear your coach apart looking for an obscure problem get Cummins to check the compressor output. I did have a leaky air bag in front and I rebuilt the air dryer (bad check valve) but having done all those it was still slow to air up unless I ran the engine fast. I did replace the idiot lights with pressure gauges so I can spot any future problems early.

[EngineerMike]

You can check the compressed air system by adapting a simple 0-160 (common pressure range, probably available for about $12 @ HD or Lowes but you'll need a coupla fittings including the Amflo type air chuck nipple) pressure gauge for insertion into the air hose fitting supplied on Alpines for at least some time, maybe forever. On my 06 it was in last bay, behind batteries; on 08 it is in PS tank bay. I plug in my gauge and watch pressure go to about 135, then cycle down as it is used in bags, etc. to about 120, then up to 135, repeat, repeat. If you know what the compressor (& blow-off, & bags, etc.) usually do after doing this exercise once, you can recheck at any time to see the compressed air system is operating properly.

[OldForester]

I am thinking it is the air dryer issue as EMike says, so we are going to check that and service it at the dealer next week. His thought is also the air dryer. As I said earlier, there's no issue maintaining air pressure after it warms up a while and we've moved it a quarter mile or so with repeated stop and starts. It can't be leaking when warm, because I can stop it after driving for no more than 15 minutes or so, shut it off for a few hours and then start it up and drive away with plenty of air pressure in the bags. It's just overnight, after dumping air, and when it's cold, and it only lasts until I go through this stop/start routine.

[EngineerMike]

For those who are tempted to swear at their Alpines due to maintenance issues, here is a note from a Country Coach owner about the air dryer maintenance:

We purchased a replacement cartridge from CC a few years ago (close to $200) and intended to have the existing one replaced. I had Buddy Gregg price the labor in Knoxville and I believe that they estimated it at 5 - 6 hours after putting the coach on a lift. Its above the axle and I believe that there are a number of things that have to be disconnected in order to get it out. They were not very enthusiastic about it, and I wasn't ready to bite the bullet. I also had a local mobile mechanic look at it and he didn't want to try it without a lift. Not a very smart design for something that should be replaced periodically. I need to get it done sometime, but.........
The Alpine drier location is easily reached behind the air filter on coaches up thru 07 and ahead of the air filter on 08/9's.

[Algoma]

I purchased my replacement cartridge on E-Bay for about $25. You may also need to replace the purge valve if it has not been looked at for a long time. Also have a look at the check valve on the output side. The Bendix instructions are very detailed on how to do this service. What is not clear is that most Cummins engines use the "AD-9 Drop-In" version which is identified by a small hose that goes from the output of the dryer back to the input side. Only matters if you go for an exchange unit as the other parts are common.

[Coin-Op]

The air dryer on my coach has a small amount of oil in the purge exhaust. Per a call to Mark @ Haldex technical services 1-800-643-2374 "Haldex Purest Air Dryer should be inspedter every year. If green residue is found on the middle or edges of the filter its time to replace it, also if purge exhaust has oil in it replace the filter.

[Old Rv'er]

Well, when I get home I will do mine, since the coach was built in 06 as an 07 and was not purchased until 08, so it must be due if for no other reason than age.

Basil - APEX owners, was/do/is there a manual from WRV just for APEX's? If so can someone make me a copy as all I have is the Limited SE manual.

We are in Castle Rock, CO and snow is forcast for Thursday - Sunday. I am here for an aqua hot class.

[Basil Shannon]

Quote:

Originally Posted by Old Rv'er Basil - APEX owners, was/do/is there a manual from WRV just for APEX's? If so can someone make me a copy as all I have is the Limited SE manual.

Yes, there is an Apex owner's manual. I could run you a copy of my 2006 manual but it peculiar to my coach. The plumbing & electrical diagrams are different since I moved the washer/dryer from the back to forward of the toilet, added a 3rd AC unit, etc. A copy of a standard 2007 Apex manual would be better for you.

[Old Rv'er]

I will start a new thread, so all the apex owners can reply. The manual I have covers most of the issues, but we are a special breed. Thank you for your reply.