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Topic: We have a situation. Cycling air pressure  (Read 1024 times) previous topic - next topic

We have a situation. Cycling air pressure

Rolling down interstate 65mph and both air gauges are cycling. They pump up to 120 and after 30 secs, they slowly go down to 100psi, then pumps back up! Normal operation? Possible leak? Suggested actions.
Thanks

Re: We have a situation. Cycling air pressure

Reply #1 –
Yes, something is wrong.  That is way too fast for air pressure to cycle from cut-out to cut-in.

Could be an air leak, could be a defective air dryer, etc.

But, DO diagnose and fix this.

Re: We have a situation. Cycling air pressure

Reply #2 –
Hi John,
When you come to a rest area or someplace you can safely park, leave the engine running and lift your engine hatch. When you hear the compressor kick off shut off the engine from the rear and listen for air. Most likely the dryer, but could be a hose. If it is the dryer, follow this thread.

Air Dryer Bypass Demo

Chuck

Re: We have a situation. Cycling air pressure

Reply #3 –
We stopped at a truck stop. It was chilly this morning, high 30s. Any chance the temp affected it? Cycle times have increased with no action from me. Cycle time of the compressor is now about 4.5 minutes. What is normal cycle time?  Thanks all.

Re: We have a situation. Cycling air pressure

Reply #4 –
Cycle time depends on air use of suspension and brakes.  No average time is recommended as a diagnostic tool.

If suspension is aired up and you are not on the brakes, while parked, you could well more than make it through happy hour before it cycles.

As several of us have already said, the air dryer, particularly if it has not been replaced in the last 3 year would be atthe top of the "suspect list", particularly if cycle times have now increased.  Not likely a large leak would "repair itself", but a sticking valve in the dryer could.

Re: We have a situation. Cycling air pressure

Reply #5 –
If you are stopped then there is no up and down wheel movement from driving and less air gets used by the ride height valves. A rough or uneven roads will use more air.  Do your air pressure gauges show pressure when you tuen the ignition off?  If ao watch to see what happens in 10 min or so.  If they do not then wait 10 min and turn the ignition on to power the gauges.

If you are using more ir while driving then it could be either of the six pack level control manifolds or a ride height control valve.  Or any number of other parts in the air system.

Re: We have a situation. Cycling air pressure

Reply #6 –
Ok, after sitting 15 min with engine off, the top air gauge has held steady at 110 psi, bottom air gauge has bled off 4 pounds to 106.

Re: We have a situation. Cycling air pressure

Reply #7 –
First things first, Navybean, welcome to the list, and congratulations on purchasing your last motorhome first.
Secondly, I imagine it's tough your not being able to hand your new-to-you Foretravel off to the crew chief with a list of repair items, but really, everything is going to be alright.  We're here for you.

Roger and Susan!  Do I understand correctly that the air suspension doesn't have a built in time delay when traveling over undulations in the pavement?

Art & Lynn

Re: We have a situation. Cycling air pressure

Reply #8 –
Funny thing watching the air gauges cycles, took a bird strike to the right windscreen! No damage just a loud thud and back to watching the gauges!

Re: We have a situation. Cycling air pressure

Reply #9 –
Seems to be acting normal now! Will let you know down the road how it is going.

Re: We have a situation. Cycling air pressure

Reply #10 –
There may be some time delay but this is mechanical system. Tire goes up relative to coach, ride height valve lever goes up which signals the level manifold to add air to the air bag to push the coach up.  On a smooth road not much happens. On a wavy road or on a windy day this is busy.

Re: We have a situation. Cycling air pressure

Reply #11 –
John,

Again, your symptoms suggest an air dryer needing replacement/complete service.  Put that on your short term "to do list".

My recommendation is a FACTORY (i.e. the factory that made it) reman.  Everything but the metal housing would be brand new-- valves, filters, heater, but prices less than brand new. I would not get a "replaces XX" dryer that may/very likely is of lesser quality.

Re: We have a situation. Cycling air pressure

Reply #12 –
Thanks all! My blood pressure is getting back to normal.

Re: We have a situation. Cycling air pressure

Reply #13 –
Quote from: wolfe10 –
John,

Again, your symptoms suggest an air dryer needing replacement/complete service.  Put that on your short term "to do list".

My recommendation is a FACTORY (i.e. the factory that made it) reman.  Everything but the metal housing would be brand new-- valves, filters, heater, but prices less than brand new. I would not get a "replaces XX" dryer that may/very likely is of lesser quality.

What would be your choice new DA34100 at $341 or DA33100 remanufactured for $254.  I have had no luck in determining how the newer model is different/better?? 

Re: We have a situation. Cycling air pressure

Reply #14 –
Tommy,

Suggest you e-mail Haldex and ask:

Are all connections on the new generation the same as your current one (provide model number of old one)?  Assume the reman unit IS.

What are the advantages of the new generation dryer?

Yes, inquiring minds want to know.

Re: We have a situation. Cycling air pressure

Reply #15 –
As Roger says, rough or winding roads use more air as the ride height valve levers move to add or dump air. I would also add that a properly adjusted ride height valve has a neutral or dead spot before the orifice lines up. In other words a very slight movement of the tire doesn't add or dump air until the orifices inside the valve line up. More movement of the levers progressively opens or closes the valve. It isn't a binary (on/off) process, but rather a linear progression. It isn't quite the same as the HWH Active Air used these days, but the system does a pretty good job at counteracting body roll under most conditions. When driving twisty roads with the driver's side window open, I can hear the system dumping air from the high side when there is a hillside to reflect the sound back to me. I have always been impressed with how little body roll on winding roads. It is especially easy to notice when going up or down a tight radius onramp. Love the stability of the ride! Having had a school bus driving job one summer in which I would sometimes feel like the bus was going to tip over in those situations, I was immediately sold by how stable our coach felt from the very first test drive.
Don

Quote from: Roger & Susan in Home2 –
There may be some time delay but this is mechanical system. Tire goes up relative to coach, ride height valve lever goes up which signals the level manifold to add air to the air bag to push the coach up.  On a smooth road not much happens. On a wavy road or on a windy day this is busy.

Re: We have a situation. Cycling air pressure

Reply #16 –
The rear more than the front, every coach lean or suspension movement is a dump & fill operation, many times a normal situation.  Faster, bumpier, turning cause air loss. If driving slow on smother roads reduces the air loss everything may be normal.

Re: We have a situation. Cycling air pressure

Reply #17 –
Quote from: wolfe10 –
Tommy,

Suggest you e-mail Haldex and ask:

Are all connections on the new generation the same as your current one (provide model number of old one)?  Assume the reman unit IS.

What are the advantages of the new generation dryer?

Yes, inquiring minds want to know.

Per Tech support at Haldex: 
The DA33100X is a screw on filter and the Da34100 is a bolt on Filter.  So if space is a problem when replacing the filter the DA33100x needs about 1" more clearance to change the filter.  There is no performance difference in the two. Earlier models of DA34100 did not match bolt pattern, but I believe current ones provide a bracket to match?
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Re: We have a situation. Cycling air pressure

Reply #18 –
Went out today to start to replace the air dryer. Raised the coach and attempted to place safety stands. I have the 12 inch harbor freight specials. All would go in except the left front. It was about 1/2 inch short. Tried a second time with same results. Left side amber light illuminated on HWH panel. I then heard a significant air leak from the driver side rear. Located a pin hole leak in one of the air bags.  1. Would this cause the cycling of the air system that I experienced at the start of this thread? 2. How to proceed? It is the forward left rear airbag. I think 8 new bags are in my future but in the meantime, how hard is it to replace that particular bag? Does Napa carry the bags?

I removed the safety stand in front to avoid twisting the coach.  4 stands in place on the rear.

Thanks in advance. Complete newb, feeling a little overwhelmed, but still in the fight.

John

Re: We have a situation. Cycling air pressure

Reply #19 –
That could have been your air leak at the beginning. Changing one air bag is not a good idea. If you are going to change all of them there is a thread about air bags less than $100 posted recently. If you are not going to change them yourself you could stick a tubeless tire repair in the hole to drive to where you would have it done. Many members have done it themselves including me. Read all the posts before attempting as there are several different ways to do it. I did it without removing the fenders and it made the job much more difficult. Sometimes to get one of the front safety stands in, after raising I raise the rear on the side the stand wouldn't go in on and then install the stand.