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Old 11-19-2022, 09:00 AM   #1
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Urgent - Can't Depart - Air Bags won't Air Up - Can I manually air them up?

Current situation - Everything prepared to leave, air bags would not air up. I cycled the jack system 3 times completely but no joy - I can't travel until air bags are up

Background -
Unit - 2008 Tiffin Phaeton, 40' DP, 25,000 miles on it, freightliner chassis Cummins engine, HWH leveling and slide system (for 2 slides)
Prior issue -
- about 6 months ago once the air bags didn't air up, I called freightliner, they said it was either the front ride height controller or the pilot dump valve. They told me to cycle the system and retry. I cycled it and it aired up. They told me it was likely a particle in the front ride height controller, it cleared and so now should be fine, nothing else to do
- later this repeated. cycling it resolved repeat problems.
- I replaced the front ride height control valve (Haldex from freightliner)
- One time I arrived at a campground and the system wouldn't dump. Upon leaving everything worked normally, and it worked normally at the next park.
- In October 2022 I stopped at Bay Diesel in Red Bay, I had them replace the rear ride height control valves (Haldex from Freightliner) and the freightliner pilot dump valve. They also adjusted the ride height to specs all around.
- Subsequent to Red Bay, I parked twice and the system operated normally
- So 3rd park since Red Bay, I arrived everything worked normally. upon leaving after 2 weeks everything when normally except the air bags won't inflate. I cycled the system 3 times. I opened the HWH control panel at the dash and checked the connector on the back and it seemed well set. I checked the wiring plugs on the main control board and plugs seemed well set.
- I believe I can manually push a button on the freightliner pilot dump valve under the RV and manually inflate the air bags. Has anyone done this? is there any safety issue in doing this? I would have to find a way to raise the unit to be able to get under it to the pilot dump right behind the generator.
Thank you in advance
- Is there any other way to manually inflate the air bags?
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Old 11-19-2022, 09:15 AM   #2
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Try releasing the parking brake and/or start engine and put in gear. Push "Stow" button on touch pad.
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Old 11-19-2022, 09:25 AM   #3
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With your tanks at pressure, engine off, do you hear any air leakage?

There is a PPV (Pressure Protection Valve) between the tanks and the suspension to save tank pressure for brake operation in the event of an air bag failure, your issue sounds like the PPV is not allowing air into the suspension system.
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Old 11-19-2022, 09:31 AM   #4
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where is PPV located

where is that PPV valve located?
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Old 11-19-2022, 09:39 AM   #5
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I had the same thing occasionally with our Phaeton about three years ago. Believe it or not it was the master solenoid on the HWH pump that was not passing power to the dump valve. I could cycle the ignition off and on a few times and it would go to working. I replaced the solenoid and have not had any problem since. Measure the voltage across the large terminals when the coach is in "slides ready" condition (parking brake set and key on) to see if the voltage is the same. If it's not, the solenoid contacts are burned or corroded. You can jumper across the two large terminals to pass power. Also, check all of the inline fuses on the hydraulic pump as power to the dump valve is controlled through the HWH controller.
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Old 11-19-2022, 09:45 AM   #6
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Quote:
Originally Posted by swduns View Post
where is that PPV valve located?
With 10 years between our chassis being built, I cannot say where it would be on your Freightliner chassis.

You'll need and air system diagram from Freightliner.
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Old 11-19-2022, 09:48 AM   #7
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I released the air parking brakes, put it in gear, then put the air parking brake back on and the bags air'd up

Clearly I still have a problem but I'm going to travel and fix the root problem at my next destination.

Thanks for everyone's input
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Old 11-19-2022, 11:13 AM   #8
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Take a look at the back side of the parking brake and clean any electrical connections. Also, the parking brake valve at the back side of the instrument panel may be going south on you.

When you can, crawl under the MH and locate the valve that controls the air. It will probably be behind the generator and in front of the fuel tank, up high with several air lines into the main body. It is about the size of an adult hand with modules on each-side end. The modules have two wires each. The modules are the solenoids that move the valve. There are two brass buttons on the bottom. The passenger side is the dump side the driver's side is the inflate side.

Take the solenoids free of the valve body. There is a small, about 1", set screw that backs off and allows the solenoid to be removed. Remove the solenoid and clean it with Scotch Brite or similar and reinstall. Those solenoids are on a shaft that can get corroded.

Good luck with the fix and safe travels.
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Old 11-21-2022, 08:33 AM   #9
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I made it to my destination with no problem
I'm here for 6 weeks so I plan to find the root cause of this problem while I'm here.
Sadly one of my two furnaces quit early this morning so I have to fix it to. It is only two years old. I didn't get into RV'g just to work on it constantly .....

Given I was able to air up the air bags after cycling the parking brake and putting it into gear .... does that provide a clue as to the source of the issue ... does that say its not the HWH system signal to the pilot dump valve and its not the dump valve (new), but something in the air system, like parking brake valve, PPV or other?

Thoughts?

I plan to call Tiffin and Freightliner. I've pulled the air brakes pneumatic diagram and have been studying it. I'm an engineer but an electrical engineer. I'm figuring the pneumatic diagram out but its taking time to figure out ... what is a inversion valve/what does it do, etc ... also I've read the literature on the HWH system. The LED lights on the control panel seems like they will provide a clue, assuming the air bag issue can be repeated and sustained while I trouble shoot it .... I don't enjoy this side of RV'g ....
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Old 11-21-2022, 10:48 AM   #10
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I read in a HWH trouble shooting paper some time ago about the retraction of the jacks and the inflation of the air bags. The publication said to always press the STOW button when starting the engine in preparation to move the MH. That would place the shuttle valve on the manifold to the driver side of the manifold and allow the air bags to inflate. The shuttle valve in the manifold moves to the passenger side to deflate the air bags. With that note, I would have to assume that the issue of the bags not inflating is not an isolated occurrence. They also mentioned that releasing the parking brake or placing the transmission in gear would accomplish the same thing, airing up the bags.

My approach would be to follow that procedure as stated and see what you get. Replacing the manifold valve is about a $400 item, if I remember correctly. I think the bags not inflating is just a thing that happens when the retraction of the jacks and the inflation of the bags get out of sequence. Pressing the STOW button realigns the sequencing and makes the system happy.
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Old 11-23-2022, 10:00 AM   #11
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Quote:
Originally Posted by rvbiker45 View Post
I read in a HWH trouble shooting paper some time ago about the retraction of the jacks and the inflation of the air bags. The publication said to always press the STOW button when starting the engine in preparation to move the MH. That would place the shuttle valve on the manifold to the driver side of the manifold and allow the air bags to inflate. The shuttle valve in the manifold moves to the passenger side to deflate the air bags. With that note, I would have to assume that the issue of the bags not inflating is not an isolated occurrence. They also mentioned that releasing the parking brake or placing the transmission in gear would accomplish the same thing, airing up the bags.

My approach would be to follow that procedure as stated and see what you get. Replacing the manifold valve is about a $400 item, if I remember correctly. I think the bags not inflating is just a thing that happens when the retraction of the jacks and the inflation of the bags get out of sequence. Pressing the STOW button realigns the sequencing and makes the system happy.
Thanks for your feedback, I hunt down that HWH troubleshooting verbiage. I did have the dump valve replaced last month at red bay as well as the 3 ride height control valves. when a problem is intermittent it is hard to troubleshoot. unfortunately the problem occurs when its my last day at a park and I've planned to leave early due to a long drive. I'm currently at my son's farm for 6 weeks, for the holidays, and I will operate the system several times while I'm here to see if it reoccurs and I can troubleshoot it
There are several methods of troubleshooting - One troubleshooting method is - Troubleshooting by substitution - which is replacing parts and see if that fixes it. That is what I've done to date as the problem is intermittent. I was wondering how cycling the parking brake resolves the problems so your info is helpful.

Note - I have been talking to freightliner, tiffin, bay diesel, and HWH in an effort to track down the problem.

thanks for your feedback
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Old 11-26-2022, 05:17 PM   #12
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What model of HWH leveling system do you have?
I have a 610 and I manually dumped my air bags (pressed dump on control panel) but didn't drop the leveling jacks. A while later I tried to air up by starting the engine and it wouldn't air up. I decided to air it up by connecting my shop compressor to the front air inlet (actually had to change it to the "new" standard air inlet connector), which happened.
Then I dumped the air by pressing the on button twice and it dumped as expected and leveled. Then I pressed "Store" and the system operated as expected.
The next time I started the engine, the coach aired up as expected.
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Old 11-27-2022, 07:40 PM   #13
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My HWH system is a 625 series system
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Old 11-29-2022, 11:26 PM   #14
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Quote:
Originally Posted by RKins View Post
What model of HWH leveling system do you have?
I have a 610 and I manually dumped my air bags (pressed dump on control panel) but didn't drop the leveling jacks. A while later I tried to air up by starting the engine and it wouldn't air up. I decided to air it up by connecting my shop compressor to the front air inlet (actually had to change it to the "new" standard air inlet connector), which happened.
Then I dumped the air by pressing the on button twice and it dumped as expected and leveled. Then I pressed "Store" and the system operated as expected.
The next time I started the engine, the coach aired up as expected.
The dump valves are installed by the coach mfgr. and are not part of the HWH leveling system. When dump only is selected, the 12V dump valves remain open when the HWH panel is turned off. Thus no air to springs.

When the entire sequence is not completed, the computer sorta loses it place. It cost me $160 to learn that from a mobile repairman.
What you did allowed the HWH control box to regain its memory-so to speak.


swduns; HWH 625 leveling system service manual
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