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Topic: Step cover (Read 550 times) previous topic - next topic

Step cover

Could someone explain how the air operated step cover works. Mine closes with good force but suddenly it has to be pushed closed. A good start would be how to get to the working parts.
Dub McBride 1996 270

Re: Step cover

Reply #1 –
Don't know much about 96 model year, I have 91 GV.
If they are using same mechanism, Most likely the cylinders need to be cleaned.

Air cylinder has two port controlled by 5 way air solenoid. 

One for air input, two for each air cylinder. On each cylinder one to push the rod out. the other port to push the rod in.

Very simple mechanism.

See  1991 Grand Villa Air step help for more information
1991 Grand Villa U300

Re: Step cover

Reply #2 –
Nice write up, think I've got this now. Thanks
Dub McBride 1996 270

Re: Step cover

Reply #3 –
Outside fold-down step and inside step-slide are controlled by compressed air.

Air brake tanks located above front axle have protection valves that supplies air to steps whenever tanks are above about 70 psi.

Outside drop-down step uses two matching dual-port air cylinders located in space behind the hinged step. On the outside backside of this space is a 12-volt pneumatic 4-port valve that controls the drop-down step. Control is automatic with valve's 12-volt ignition power going through a normally open magnetic switch mounted near door hinge.

When the 4-port valve has 12-volts, like when ignition is on and door is closed, compressed air is directed to the cylinder's open-end port retracting piston, pulling step closed. When 12-volts is not flowing to valve because ignition key is turned off OR door is opened which opens magnetic switch, the 4-port valve redirects compressed air  to the cylinder's closed-end port extending piston, forcing step down into open position. Air pressure will continue to force piston to remain in open down position until air tank gets below the protection valve setting which then cuts off all air pressure. Gravity will continue to keep step down.

Our coach has a seldom-used hidden toggle switch that uses battery power to simulate ignition being on, to force step up if there is air pressure and door is closed. This option can be helpful for increased security or if parking next to a high curb.

The 4-port valve has an input air pressure port, output port to closed end of cylinder, output port to open-end of cylinder, and exhaust port. When piston is moved with air pressure at one end of cylinder, the other end's port is directed to the valve's exhaust port allowing the piston to freely move. To slow down piston movement and prevent step slamming in each direction, the valve's exhaust port has an adjustable restrictor/damper that slows down air leaving cylinder.

The inside step slide uses an another identical 4-port valve also mounted on backside of step that directs air pressure to a single dual-port air cylinder that is attached to the center of the slide. Power to pneumatic valve is from two switches wired as 3-way, with one by driver's right knee ( which we never use ) and the main switch by the door on the cup-holder stand. The two switches will change each other's on & off position, so we leave driver's switch alone and use door switch with up for step covered & down for cover retracted.

It is felt that if step slide cylinder fails by leaking air pressure, it's location can make it difficult to replace. So, we made a modification to not keep cylinder seals under air pressure all the time. We can manually turn off air supply to cylinder after it moves fully open and closed. Without air pressure to keep the slide in position, slide could move on its own, but with horizontal movement drag, it never moves. But it can be manually pulled opened or pushed closed if desired when air pressure is exhausted.

For the outside hinged step, it is important that it always be forced down with air pressure, when door is opened, so we did not make any similar modification to extend the life the outside step cylinders.

We manually turn off air pressure to the inside step slide's 4-way pneumatic valve with an add-on 3-way valve on the air supply line that closes it off and also exhausts captive cylinder air pressure. This added-on valve is controlled by a small toggle switch next to the step slide switch on the cup-holder stand by the door.
 

Re: Step cover

Reply #4 –
That's a fantastic write up! I'm saving a pdf of this into my Foretravel files. Thank you.
1998 36 foot U270 Build No. 5328 WTFE, 900 watts solar, Victron controller, B2B, bat monitor, 600 AMPH lithium with 2018 Chevy Colorado toad, SKP #110239, Motorcade #17781, 2021 Escape 17B for when Coach is broken down and campsites are too small, retired and full-timer since Dec. 2020. Part of RV family since 1963.