Slides and altitude

Here is an interesting one. We are presently on an extended trip that covers areas from sea level to over 12,000 feet. The bus has been parked from sea level to 9700 feet. At sea level up to 5000 feet both slides work normally. Above 5000 and to 7000 feet I get an error when trying to open rear slide. The error message translates to "cannot deflate seal." I checked the pressure and it is normal at 7-8 lbs. Above 7000 both slides have error message and very difficult to either put slides in or out. Then traveled back down to 5000 feet and slides work normally again.

Any ideas? Has anyone else had similar problems?

Thank you

Hi Kim. That is very interesting. In McCall, Idaho the elevation is around 5000 feet and I have had no problems. I would think the seals are expanded a little more maybe and the presets for deflating are not recognizing the seals are not fully deflated. Maybe if you adjust the pressure down a little it would be enough of an adjustment so the seals would deflate totally.

Hello Gary,

I tried that, and did not get any change. I will be at 7500 feet Sunday, and will try that again. I guess this bus, made in Florida just does not like the higher elevations. I am going to try and call Bill Jensen to see if he has any ideas. I will try on Wednesday when have a break from work. At the present time I am in NJ, while the bus is in colorado.

What exactly do you mean when you say very difficult to open?

Going slow, excessive draw, noises, hard getting released and locked?

I think I would be worried about doing other damage.

I agree, very curious problem. You seam to be on to something.

Kim, I would suspect that it is the atmospheric pressure causing the problem. We brought a couple bags of potato chips with us when we first arrived at Yellowstone, and they expanded to almost twice the size. I was told that sometimes many of the bags in the grocery store will expand until they blow up. I suspect the added pressure is causing problems with your air seals. Hopefully, there is a simple solution.

Dale has it right.

If you deflate a slide seal to some value such as 3 PSI at sea level, that internal pressure increases as the altitude increases.

That suggests to me that the deflation portion of the cycle is a timed event rather than controlled by a pressure switch. The engineers probably set the control sequence allowing some time value for deflation. I find that odd because if the system senses internal seal pressure, wouldn't it make sense to use the pressure it senses to advance the sequence to the next part of the cycle instead of just reporting an error?

Hello everyone,

With the Prevost slides the air seal must be deflated prior to the pins unlocking. If the system does not think the seals are delflated, the pins will not unlock, and the slides will not move. You get an error code which translates to the seals not being deflated. That is what happens in the coach.

If trying to close, the seals also have to deflate prior to the motion of the slide.

I feel the altitude is causing the problem; however, I do not understand why.

The good news is that the problems have for the most part been in moving the slides OUT. WE are able to live very easily without the slides out. If this happens in moving the slides in, then we are going to have to use the manual override which is NO FUN.

Kim,

I will be interested in the diagnosis / solution. Where do you get the error message? We just returned from a trip to Montana and Wyoming and had no trouble with deployment of the slides. Of course, our highest camping elevation was in West Yellowstone, MT which is about 6,700 feet elevation. We would like to take the bus to Colorado next summer for some Jeeping. We like to go to Creede which is at 8,800 feet elevation and Breckenridge at 9,600 feet elevation. Please let us know what you learn.

Loc

The message actually comes from the light on the slide switches. Checking the documentation with the coach shows that two flashes (quick and short) followed by a space equates to the seal not deflating properly.

Well, e have the answer. I spoke with Bill Jensen of Prevost today. He is always willing to help, and a wealth of information. As soon as I started to describe the problem he knew the answer.

When at altitude some coaches with slides have this problem. It relates to how much of a column of mercury (pressure) the switch must see to for it to think that the seal has been completely deflated. If you follow the line from the pressure rheostat you will find a switch for each slide. Just above that there is a small straight headed screw. Turn each of those (one for each slide) 1 turn clockwise. Then the switch will recognize when the vacuum has been achieved even at altitude.

I will be back at 7000 feet Sunday and will let you know if this has worked. I am sure it will since Bill knew exactly what the problem was when I spoke with him.