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Old 05-27-2014, 08:01 PM   #1
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RV levelers theory of operation?

The other evening around the campfire I was musing as to exactly how RV levelers operate. On my Sightseer with Power Gear Jacks, the fronts go down first. What determines how far they initially go down. Is it a set time of hydraulic pump on? Is it determined by an electronic level sensor? Is it determined by a certain volume of fluid pumped?
Then the rear levelers come into play. Am I correct in assuming at this point that an electronic sensor determines how far they go down?
Finally, side to side leveling occurs using only the left or right rear levelers, which I also assume is determined by an electronic level sensor. Then they continue fine tuning until I end up pretty high.
If I use automatic leveling the chassis always ends up much higher than if I use the manual mode. It does end up level in auto mode so I assume the level adjustment setting is correct. It would sure be nice to pull in and hit auto level and be done with it and not be so high up.

If you know the theory of operation I would love to hear it.

If you have an answer as why auto level ends up higher than I think necessary, that would be great also.
Thanks,
Al
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Old 05-27-2014, 09:19 PM   #2
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Depends on your make/model leveling jacks mfgr. I have HWH hydraulic leveling jacks. When I touch the on button twice for automatic leveling mode, the fronts extend (assuming I'm on a front-low site) until the leveling sensor detects movement, it pauses a second then continues the sequence by further extending the front jacks until the sensor detects side-to-side level must be corrected, once side-to-side is level it continues front-to-back leveling, once that is accomplished the jacks not used to accomplish level are extended until movement is detected(for MH stabilization), then the system extends or retracts jacks to again correct level requirements.
I do not have any documentation or proof that is how HWH designed this system, that is just how mine work.
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Old 05-28-2014, 11:03 AM   #3
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Hi Ray,
Thanks for the response. Sounds pretty much as expected. Do you have any idea of how the system senses movement and when to stop. Do you think that there may be pressure sensors as well as the level sensor involved in the process? I see that you mention that yours will actually retract a jack in certain situations. I pretty sure that mine wont do that. Perhaps it's one reason mine ends up so far off the ground.
Al
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Old 05-28-2014, 12:23 PM   #4
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The leveling sensor determines everything. It's location is determined by Winnebago, most of the time the leveling sensor/board is underneath the coach. There is a thread in this forum discussing it in detail. my leveling board/sensor went bad.fI had it repaired under the GS extended service contract, and the technician moved the mounting location to the LF basement compartment ceiling, which is very convenient for re-adjusting level condition.
I don't think there are pressure sensors involved, it's all determined by movement of the leveling board.
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Old 05-28-2014, 03:34 PM   #5
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I also have the Power Gear jacks. They operate differently than HWH. When they level side to side, they raise the low rear jack and lower the opposite front jack. In order to accomplish this they raise the front end higher than might be necessay.
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Old 05-28-2014, 07:40 PM   #6
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Thank you for the replies. I wonder how many successfully use the auto level feature vs those that manually level to keep the coach height to a minimum and doesn't require using an extra step outside to climb in comfortably?
Al
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Old 05-30-2014, 02:57 PM   #7
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Quote:
Originally Posted by atodalen View Post
Thank you for the replies. I wonder how many successfully use the auto level feature vs those that manually level to keep the coach height to a minimum and doesn't require using an extra step outside to climb in comfortably?
Al
atodalen,
Our coach, an '04 Itasca Horizon 36GD with the C-7 330 CAT, is equipped with the HWH 625 Computerized Leveling System. I have two PDFs that explain the exact sequence of events for that particular system. Now, for one thing, it may (most likely will) have somewhat different operating characteristics based in a gas rig or a diesel rig. The reason, not many gas units have air bag suspension that I know of. So, with the 625 system, the air has to be depleted prior to the jack system beginning it's operation.

And, using an auto leveling system is kind of dependent on just how far off level you are, prior to beginning. I make the decision to use the Auto feature as opposed to doing it manually. If I determine the system will be over taxed because of too far off level in the beginning, I compensate in a multitude of ways. And then, I use the manual system. But, that's another story.

Anyway, many campgrounds/RV Parks, have somewhat fairly level spots. If that's the case, I use the Auto level system. And, this is the way it works, as described in the HWH manuals.

1. The parking brake set, the ignition is turned OFF.
2. Then, you can use the ACC position of the ignition switch for the next part.
3. Push the "On" button once to turn the system on.
4. Push it again, to start the Auto Leveling system.

When that system is activated, it takes over the depleting of the air bags. When they've been bled for approximately 20-25 seconds, the jack system is initialized.

5. The system looks for "Yellow" lights on the control panel. Those indicate which side/end is un level.
6. If it sees a yellow light on either side, it will begin sending down those jacks on that side which displays the yellow, un level light. It will continue sending the jacks down, and, upon contact with the ground, will raise the coach, on that side, 'till the yellow light is out.

7. Then, it will extend the jack that represents the un level end, based on the yellow light. Upon contact with the ground, it will run "both" jacks (one's already in contact with the ground from the previous operation) until the yellow light is out.

At this time, there are only three jacks down.

8. Now, it will send down the fourth jack. Upon contact with the ground, it (that jack only) will raise the coach, approximately 3/4" to 1", just for stabilization. Once that "inch" is seen by the auto-level sensor, the entire system is shut down and turned OFF.

And that's how the 625 Computerized Leveling System is supposed to work, based on how the manual states it. Ours does all those steps, in that order, each and every time, to the letter. It has never lifted the coach, any higher than it needs to, to achieve a level status. I've read many times that folks have coaches climb way to high, using the auto level system.

I guess we've been lucky. When we begin the leveling operation, the coach drops around 3"-4" inches due to the depletion of the air bags. Then, the jacks, again based on a somewhat fairly level pad, will raise it, approximately the same 3" - 4", based on what it (the sensor) sees it needs to accomplish full level. If I over estimate it's (The Auto leveling) capability, it will let me know. It does so by prematurely shutting down the system and telling me on the panel: "Excessive Slope" If I see that, then take over manually and compensate as needed.
Scott
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Old 05-30-2014, 03:53 PM   #8
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I have a 2008 Winnebago Destination 39W with the Kwikee hydraulic leveling system. The leveling sensor takes care of it all, but in my case the left sides come down first, then the right side, then whatever is needed to level. In the Auto Level mode it does give it an extra kick or two versus using the manual mode but that makes the coach much more stable. When I do use the manual mode I will bump up each side just a little to obtain that stability. Just touching the surface to level will still allow the coach to rock when walking in it.

There are time, and the manual states, that when leveling one jack could be off the ground (not touching the groudn). In that case I will manually extend that side. When doing this the jack that is touching will not move until the one not touching hits the ground, then they will both raise that side. When I feel the bump I stop or extend more for stability.

My control lights work differently than previously described. When all lights are lit I am level. The unlit lights are the side that needs leveling and the auto-mode will bump until all lights are on. Once the coach is level a combination of two buttons on the control panel will synchronize it to that same degree of levelness.
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Old 05-30-2014, 09:42 PM   #9
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There's certainly quite a few variations in how different systems function. It seems the DPs have a leg up on us gassers in that once they dump air the leveling starts much lower to the ground. My original intent was to try and understand what makes them tick in the way of sensors, etc rather than the sequence of operation. It looks like after reading your replies that they are pretty much controlled by the level sensor alone. I thank you all for your input.
Al
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Old 05-30-2014, 09:45 PM   #10
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I could have just said, "They are controlled by the level sensor," but that would not have been as much fun.
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Old 05-30-2014, 09:47 PM   #11
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I could have just said, "They are controlled by the level sensor," but that would not have been as much fun.
Roger that.
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Old 05-30-2014, 10:33 PM   #12
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According to the operator's manual HWH jacks also make use of a pressure sensor on each jack:

Quote:
During the automatic leveling sequence, after the system has extended the appropriate jacks to level the vehicle and has turned the yellow level indicator lights off, the system will then stabilize the vehicle.... Stabilizing the vehicle is accomplished by extending any jacks to the ground that were not used to level the vehicle. This is done by monitoring a pressure switch on each jack. Any jack used to stabilize the vehicle will lift the vehicle approximately one (1) inch. This "bumps" the vehicle up slightly when stabilizing...
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Old 06-01-2014, 12:05 PM   #13
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Quote:
Originally Posted by atodalen View Post
There's certainly quite a few variations in how different systems function. It seems the DPs have a leg up on us gassers in that once they dump air the leveling starts much lower to the ground. My original intent was to try and understand what makes them tick in the way of sensors, etc rather than the sequence of operation. It looks like after reading your replies that they are pretty much controlled by the level sensor alone. I thank you all for your input.
Al
atodalen,
Yes, trying to understand many RV functions and how they "Tic" is part of, "the way the work". One can answer many of the questions on these forums with very simple and "low volume" answers but, many times, the "short" answer does not answer the question. While my answer may have been long winded, it does show and state, what happens and when it happens which, at least on my system (and many others with a DP) for the most part, explains what makes it "tick".

Yep, you can say "a sensor" does the job. But, that type of answer may, or may not help with the original question. I apologize for elaborating.
Scott
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Old 06-01-2014, 08:25 PM   #14
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atodalen,
I apologize for elaborating.
Scott
I'm sorry that what I said caused you to feel that way. It certainly wasn't my intent to sound unappreciative. One of my many character flaws I guess. I like to think of myself as a lifelong learner and try to digest as much information as possible in items that I have an interest in. You as well as others with a lot of experience have spent a great deal of time trying to help myself and anyone who asks for help and I really appreciate it. Thanks for your detailed input!
However, there is hardware and software involved to cause that sequence of events for our units to end up level without popping windshields and twisting frames and that's what I was angling for. What really is creating that sequence to occur? Call me hardheaded, but I still question whether a level sensor alone can accomplish it, perhaps with some finely tuned coding based on timing loops. But I suspect there is more to it than that. I don't know the specifics of the level sensors involved but I have doubts that they are able to tweak to the degree of knowing the difference between merely level and then going a bit further to stabilize the coach based on a binary level/not level signal. How does it know to bump it up after level for stability? It's in the code I imagine but then, how does it know how far to bump it up when stabilizing? What or how is it measured or determined? How does it know when the jack has touched the ground? cbeierl mentioned that HWH does indeed use a pressure switch on each jack according to a quote from the manual. That takes some of the mystery out of for me.

With that said, I'd sure love to see the commented coding for the Power Gear levelers, as if that's ever going to happen.

I know, who cares how it does it as long as it works. Another of my character flaws, curiosity.
Al
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Old 06-01-2014, 11:24 PM   #15
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atodalen,
No apologies necessary. You are simply digging deeper into the workings of basically a complicated system that not very many on here understand. The problem with our new and electronic world is, while it's more efficient and, modern, it's also more complicated in terms of computers and electronics that make decisions on what's what and where's where.

My explanation of how my (and other coaches equipped with the 625 HWH Computerized Leveling system) system works basically was right out of the HWH manual. Some of that wording you used is right over my head in terms of "timing loops" and others.

I know that my system works exactly how it's supposed to in the manual. And that includes the little "Bump up" for stabilization on the last operation, of the last-up jack. It could, as Chris stated, be a pressure thing on the jack itself or, it could be a timing thing based on the jack reaction after it encounters the ground which, would instantaneously, put more pressure on that part of the system. You got me partner.

As far as the coach being dead-a$$ level each and every time, using the auto-leveling system, it's pretty darn close but, not ALWAYS perfect. Every once in a while, I might, (I say MIGHT) have to bump up a side or end to my satisfaction. But, that doesn't happen very often.

When we encounter way un level camp spots, I don't even THINK about using the auto leveling system. I break out the blocks etc. and drive up on whatever's needed to preliminarily level the rig before I employ the jack system. That way, I don't do any frame twisting, windshield popping, door jamming, etc. The jacks are used for "FINE TUNING" the level operations only, in that situation. It's a bit of work that way but, it's our coach and I'm the one who has to fix it if I break it because of being lazy and trying to make a jack system do so much work. It's a preference thing.
Scott
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